Provided by: monit_5.34.2-1_amd64 
NAME
Monit - utility for monitoring services on a Unix system
SYNOPSIS
monit [options] <arguments>
DESCRIPTION
Monit is a utility for managing and monitoring processes, programs, files, directories and
filesystems on a Unix system. Monit conducts automatic maintenance and repair and can
execute meaningful causal actions in error situations. E.g. Monit can start a process if
it does not run, restart a process if it does not respond and stop a process if it uses
too much resources. You can use Monit to monitor files, directories and filesystems for
changes, such as timestamps changes, checksum changes or size changes.
Monit is controlled via an easy to configure control file based on a free-format, token-
oriented syntax. Monit logs to syslog or to its own log file and notifies you about error
conditions via customisable alert messages. Monit can perform various TCP/IP network
checks, protocol checks and can utilise SSL for such checks. Monit provides a HTTP(S)
interface and you may use a browser to access the Monit program.
WHAT TO MONITOR?
You can use Monit to monitor daemon processes or similar programs running on localhost.
Monit is particularly useful for monitoring daemon processes, such as those started at
system boot time. For instance sendmail, sshd, apache and mysql. In contrast to many other
monitoring systems, Monit can act if an error situation should occur, e.g.; if sendmail is
not running, monit can start sendmail again automatically or if apache is using too many
resources (e.g. if a DoS attack is in progress) Monit can stop or restart apache and send
you an alert message. Monit can also monitor process characteristics, such as how much
memory or cpu cycles a process is using.
You can also use Monit to monitor files, directories and filesystems on localhost. Monit
can monitor these items for changes, such as timestamps changes, checksum changes or size
changes. This is also useful for security reasons - you can monitor the md5 or sha1
checksum of files that should not change and get an alert or perform an action if they
should change.
Monit can monitor network connections to various servers, either on localhost or on remote
hosts. TCP, UDP and Unix Domain Sockets are supported. Network test can be performed on a
protocol level; Monit has built-in tests for the main Internet protocols, such as HTTP,
SMTP etc. Even if a protocol is not supported you can still test the server because you
can configure Monit to send any data and test the response from the server.
Monit can be used to test programs or scripts at certain times, much like cron, but in
addition, you can test the exit value of a program and perform an action or send an alert
if the exit value indicates an error. This means that you can use Monit to perform any
type of check you can write a script for.
Finally, Monit can be used to monitor general system resources on localhost such as
overall CPU usage, Memory and System Load.
GENERAL OPERATION
The behaviour of Monit is controlled by command-line options and a run control file,
monitrc, the syntax of which we describe in a later section. Command-line options override
.monitrc declarations.
The default location for monitrc is ~/.monitrc. If this file does not exist, Monit will
try /etc/monitrc and a few other places. See FILES for details. You can also specify the
control file directly by using the -c command-line switch to monit. For instance,
$ monit -c /var/monit/monitrc
Before Monit is started the first time, you can test the control file for syntax errors:
$ monit -t
$ Control file syntax OK
If there was an error, Monit will print an error message to the console, including the
line number in the control file from where the error was found.
Once you have a working Monit control file, simply start Monit from the console, like so:
$ monit
You can change some configuration directives via command-line switches, but for simplicity
it is recommended that you put these in the control file.
Monit will detach from the terminal and run as a background process, i.e. as a daemon
process. As a daemon, Monit runs in cycles; It monitor services, then goes to sleep for a
configured period, then wakes up and start monitoring again in an endless loop.
Options
The following options are recognized by Monit. However, it is recommended that you set
options (when applicable) directly in the .monitrc control file.
-c file
Use this control file
-d n
Run Monit as a daemon once per n seconds. Or use "set
daemon" in monitrc.
-g name
Set group name for start, stop, restart, monitor, unmonitor,
status and summary action.
-l file
Print log information to this file. Or use "set log"
in monitrc.
-p pidfile
Use this lock file in daemon mode. Or use "set pidfile"
in monitrc.
-s statefile
Write state information to this file. Or use "set
statefile" in monitrc.
-B
Batch command line mode (no tabular output and no colors). Or
use "set terminal batch" in monitrc.
-I
Do not run in background mode (needed to run from init). Or use
"set init" in monitrc.
-i
Print Monit's unique ID
-r
Reset Monit's unique ID. Use with caution
-t
Run syntax check for the control file
-v
Verbose mode, work noisy (diagnostic output)
-vv
Very verbose mode, same as -v plus log stack-trace on error
-H [filename]
Print MD5 and SHA1 hashes of the file or of stdin if the
filename is omitted; Monit will exit afterwards
-V
Print version number and patch level
-h
Print a help text
Arguments
Once you have Monit running as a daemon process, you can call Monit with one of the
following arguments. Monit will then connect to the Monit daemon (on TCP port
127.0.0.1:2812 by default) and ask the Monit daemon to perform the requested action. In
other words; calling monit without arguments starts the Monit daemon, and calling monit
with arguments enables you to communicate with the Monit daemon process.
start all
Start all services listed in the control file and enable monitoring for them. If the
group option is set (-g), only start and enable monitoring of services in the named
group ("all" is not required in this case).
start <name|pattern>
Start the named service and enable monitoring for it. The name is a service entry name
from the monitrc file. You can use a regex pattern too (note that it is case
insensitive).
stop all
Stop all services listed in the control file and disable their monitoring. If the
group option is set, only stop and disable monitoring of the services in the named
group ("all" is not required in this case).
stop <name|pattern>
Stop the named service and disable its monitoring. The name is a service entry name
from the monitrc file. You can use a regex pattern too (note that it is case
insensitive).
restart all
Stop and start all services. If the group option is set, only restart the services in
the named group ("all" is not required in this case).
restart <name|pattern>
Restart the named service. The name is a service entry name from the monitrc file. You
can use a regex pattern too (note that it is case insensitive).
monitor all
Enable monitoring of all services listed in the control file. If the group option is
set, only start monitoring of services in the named group ("all" is not required in
this case).
monitor <name|pattern>
Enable monitoring of the named service. The name is a service entry name from the
monitrc file. Monit will also enable monitoring of all services this service depends
on. You can use a regex pattern too (note that it is case insensitive).
unmonitor all
Disable monitoring of all services listed in the control file. If the group option is
set, only disable monitoring of services in the named group ("all" is not required in
this case).
unmonitor <name|pattern>
Disable monitoring of the named service. The name is a service entry name from the
monitrc file. Monit will also disable monitoring of all services that depends on this
service. You can use a regex pattern too (note that it is case insensitive).
status [name|pattern]
Print service status information.
summary [name|pattern]
Print a short status summary.
report [up | down | initialising | unmonitored | total]
Report services state. The output can easily be parsed by scripts. Without options,
prints a short overview of the state of all services managed by Monit. The option, up
prints the number of all services in this state, down likewise and so on.
reload
Reinitialise a running Monit daemon, the daemon will reread its configuration, close
and reopen log files.
quit
Kill the Monit daemon process
validate
Check all services listed in the control file. This action is also the default
behaviour when Monit runs in daemon mode.
procmatch <regex>
Allows for easy testing of pattern for process match check. The command takes regular
expression as an argument and displays all running processes matching the pattern.
THE MONIT CONTROL FILE
Monit is configured and controlled via a control file called monitrc. The default location
for this file is ~/.monitrc. If this file does not exist, Monit will try /etc/monitrc,
then @sysconfdir@/monitrc and finally ./monitrc. If you build Monit from source, the value
of @sysconfdir@ can be given at configure time as ./configure --sysconfdir. For instance,
using ./configure --sysconfdir /var/monit/etc will make Monit search for monitrc in
/var/monit/etc
To protect the security of your control file and passwords the control file must have
read-write permissions no more than 0700 (u=xrw,g=,o=); Monit will complain and exit
otherwise.
When there is a conflict between the command-line arguments and the arguments in this
file, the command-line arguments takes precedence.
Monit uses its own Domain Specific Language (DSL); The control file consists of a series
of service entries and global option statements.
Comments begin with a '#' and extend through the end of the line. Otherwise the file
consists of a series of service entries or global option statements in a free-format,
token-oriented syntax.
You can use noise keywords like 'if', 'and', 'with(in)', 'has', 'us(ing|e)', 'on(ly)',
'then', 'for', 'of' anywhere in an entry to make it resemble English. They're ignored, but
can make entries much easier to read at a glance. Keywords are case insensitive.
There are three kinds of tokens: grammar, numbers (i.e. decimal digit sequences) and
strings. Strings can be either quoted or unquoted. A quoted string is bounded by double
quotes and may contain whitespace (and quoted digits are treated as a string). An unquoted
string is any whitespace-delimited token, containing characters and/or numbers.
On a semantic level, the control file consists of three types of entries:
1. Global set-statements
A global set-statement starts with the keyword "set" and the item to configure.
2. Global include-statement
The include statement consists of the keyword "include" and a glob string. This
statement is used to include configure directives from separate files.
3. One or more service entry statements.
Service checks
Each service entry consists of the keywords "check", followed by the service type. Each
entry requires a unique descriptive name, which may be freely chosen. This name is used by
Monit to refer to the service internally and in all interactions with the user. The name
is case insensitive.
Currently, nine types of check statements are supported:
Process
CHECK PROCESS <unique name> <PIDFILE <path> | MATCHING <regex>>
<path> is the absolute path to the program's pid-file. A pid-file is a file, containing a
Process's unique ID. If the pid-file does not exist or does not contain the PID number of
a running process, Monit will call the entry's start method if defined.
<regex> is an alternative to using PID files and uses process name pattern matching to
find the process to monitor. The top-most matching parent with highest uptime is selected,
so this form of check is most useful if the process name is unique. Pid-file should be
used where possible as it defines expected PID exactly. You can test if a process match a
pattern from the command-line using "monit procmatch "regex-pattern"". This will lists all
processes matching or not, the regex-pattern.
File
CHECK FILE <unique name> PATH <path>
<path> is the absolute path to the file. If the file does not exist, Monit will call the
entry's start method if defined, if <path> does not point to a regular file type (for
instance a directory), Monit will disable monitoring of this entry. If Monit runs in
passive mode or the start method is not defined, Monit will just send an alert on error.
Fifo
CHECK FIFO <unique name> PATH <path>
<path> is the absolute path to the fifo. If the fifo does not exist, Monit will call the
entry's start method if defined, if <path> does not point to a fifo type (for instance a
directory), Monit will disable monitoring of this entry. If Monit runs in passive mode or
the start method is not defined, Monit will just send an alert on error.
Filesystem
CHECK FILESYSTEM <unique name> PATH <string>
<path> is the path to the device/disk, mount point or NFS/CIFS/FUSE connection string. If
the filesystem becomes unavailable, Monit will call the service's start method if defined.
If Monit runs in passive mode or the start method is not defined, Monit will just send an
alert on error.
Directory
CHECK DIRECTORY <unique name> PATH <path>
<path> is the absolute path to the directory. If the directory does not exist, Monit will
call the entry's start method if defined. If <path> does not point to a directory, monit
will disable monitoring of this entry. If Monit runs in passive mode or the start methods
is not defined, Monit will just send an alert on error.
Remote host
CHECK HOST <unique name> ADDRESS <host>
The host address can be specified as a hostname string or as an IP-address string on a
dotted decimal format. Such as, "tildeslash.com" or "64.87.72.95".
System
CHECK SYSTEM <unique name>
The unique name is usually the local host name, but any descriptive name can be used. If
you use the variable $HOST as the name, it will expand to the hostname. This check allows
one to monitor general system resources such as CPU usage, total memory usage or load
average. The unique name is used as the system hostname in mail alerts and as the initial
name of the host entry in M/Monit.
Program
CHECK PROGRAM <unique name> PATH <executable file> [TIMEOUT <number> SECONDS]
<path> is the absolute path to the executable program or script. The status test allows
one to check the program's exit status. If the program does not finish executing within
<number> seconds, Monit will terminate it. The default program timeout is 300 seconds (5
minutes). The output of the program is recorded and made available in the User Interface
and in alerts, by default up to 512 bytes. You can change the output limit using the set
limits statement).
Network
CHECK NETWORK <unique name> <ADDRESS <ipaddress> | INTERFACE <name>>
<ipaddress> is the IPv4 or IPv6 address of the monitored network interface. It is also
possible to use interface name, such as "eth0" on Linux.
LOGGING
Monit will log status and error messages to a file or via syslog. Use the set log
statement in the monitrc control file.
To setup Monit to log to its own file, use e.g. set log /var/log/monit.log. Note, the
previous set logfile statement is deprecated, but can alternatively be used.
If syslog is given as a value for the "-l" command-line switch or the keyword set log
syslog is found in the control file, Monit will use the syslog system daemon to log
messages with a priority assigned to each message based on the context.
To turn off logging, simply do not set the log in the control file (and of course, do not
use the -l switch)
The format for an entry in the log file is:
[date] priority : message
for example:
[2020-08-12T16:35:00+0200] info : 'localhost' Monit started
TERMINAL OUTPUT
Monit uses ANSI escape sequences to colorise important parts of the command-line output,
if the terminal supports colors, and UTF-8 box characters for tabular output.
If you want to process the monit CLI output in a script, you can use either the -B option
or use the following statement in the monit configuration file to disable tabular output
and colors completely:
SET TERMINAL BATCH
DAEMON MODE
Use
SET DAEMON <seconds>
[[WITH] START DELAY <seconds>]
to specify Monit's poll cycle length and run Monit in daemon mode. You must specify a
numeric argument which is a polling interval in seconds.
In daemon mode, Monit detaches from the console, puts itself in the background and runs
continuously, monitoring each specified service and then goes to sleep for the given poll
interval, wakes up and start monitoring again in an endless cycle.
Alternatively, you can use the "-d" command line switch to set the poll interval, but it
is strongly recommended to set the poll interval in your ~/.monitrc file, by using set
daemon.
Monit will then always start in daemon mode. If you do not use this statement and do not
start monit with the -d option, Monit will just run through the service checks once and
then exit. This might be useful in some situations, but Monit is primarily designed to run
as a daemon process.
Calling "monit" with a Monit daemon running in the background sends a wake-up signal to
the daemon, forcing it to check services immediately. Calling "monit" with the quit
argument will kill a running Monit daemon process instead of waking it up.
The start delay option can be used to wait (once) before Monit starts checking services
after system reboot. Monit will by default start checking services immediately at startup.
INIT SUPPORT
The "set init" statement prevents Monit from transforming itself into a daemon process.
Instead Monit will run as a foreground process. (You should still use "set daemon" to
specify the poll cycle).
This is required to run Monit from init. Using init to start Monit is probably the best
way to run Monit if you want to be certain that you always have a running Monit daemon on
your system. Another option is to run Monit from crontab. In any case, you should make
sure that the control file does not have any syntax errors before you start Monit from
init or crontab (use "monit -t" to check).
To setup Monit to run from init, you can either use the "set init" statement in Monit's
control file or use the "-I" option from the command line. Here is what you must add to
"/etc/inittab":
# Run Monit in standard run-levels
mo:2345:respawn:/usr/local/bin/monit -Ic /etc/monitrc
After you have modified init's configuration file, you can run the following command to
re-examine /etc/inittab and start Monit:
telinit q
For systems without telinit:
kill -1 1
If Monit is used to monitor services that are also started at boot time (e.g. services
started via SYSV init rc scripts or via inittab) then, in some cases, a race condition
could occur. That is; if a service is slow to start, Monit can assume that the service is
not running and possibly try to start it and raise an alert, while, in fact the service is
already about to start or already in its startup sequence. Please see the FAQ for a
solution to this problem. The short version is to start Monit on a higher run-level after
system processes.
INCLUDE FILES
The Monit control file, "monitrc", can include additional configuration files. This
feature helps one to organise configuration into separate files instead of having
everything in one file, if you like this kind of thing. Include statements can be placed
at virtually any place in "monitrc" though the convention is at the bottom. The syntax is
the following:
INCLUDE <globstring>
The globstring is any kind of string as defined in glob(7). Thus, you can refer to a
single file or you can load several files at once. If you want to use whitespace in your
string the globstring needs to be embedded into quotes (') or double quotes ("). If the
globstring matches a directory instead of a file, it is silently ignored.
Any include statements in an included file are parsed as in the main control file.
If the globstring matches several results, the files are included in a non sorted manner.
If you need to rely on a certain order, you should avoid wild-card globbing and instead
specify the full path of files included.
An example,
include /etc/monit.d/*.cfg
This will load any file matching the globstring. That is, all files in /etc/monit.d that
ends with the prefix .cfg.
Up to 1024 include files are supported. If this limit is exceeded, Monit will report an
error.
SSL OPTIONS
Common SSL/TLS options can be set using the following statement and will apply to all SSL
connections made through Monit:
SET <SSL | TLS> [OPTIONS] {
VERSION: <AUTO | [-]SSLV2 | [-]SSLV3 | [-]TLSV1 | [-]TLSV11 | [-]TLSV12 | [-]TLSV13>, ...
VERIFY: <ENABLE | DISABLE>
SELFSIGNED: <ALLOW | REJECT>
CIPHERS: <string>
PEMFILE: <path>
PEMCHAIN: <path>
PEMKEY: <path>
CLIENTPEMFILE: <path>
CACERTIFICATEFILE: <path>
CACERTIFICATEPATH: <path>
}
VERSION set the specific SSL/TLS version to use. By default Monit uses AUTO. In AUTO mode,
only TLS 1.2 and 1.3 are allowed, all other protocols are considered obsolete. If you want
to use the obsolete protocol you must explicitly set the version. You can exclude the
protocol using the "-" prefix. Exclude list example:
set ssl {
version: auto -sslv2 -sslv3 -tlsv1 -tlsv11
} Example of allowed protocols list:
set ssl {
version: tlsv12 tlsv13
}
VERIFY enable SSL server certificate verification. This will verify and report an error if
the server certificate is not trusted, not valid or has expired. By default certificate
verification is disabled, though we recommend enabling it, otherwise there is no guarantee
that Monit speaks with the server you think it speaks with.
SELFSIGNED self-signed certificates are rejected by default. Use this option to allow
self-signed certificates. Warning: not recommended in production for security reasons, as
in such case the client cannot verify it talks to the correct server and attack types like
man-in-the-middle or DNS hijacking are possible).
CIPHERS override default SSL/TLS ciphers.
PEMFILE set the path to the SSL server certificate "database-file" in PEM format. This
options has effect only for the monit HTTP interface.
As an alternative to setting PEMFILE with a combined chain-key file, PEMCHAIN and PEMKEY
set the path to the SSL certificate chain respectively the server private key file in PEM
format. This options has effect only for the monit HTTP interface.
CLIENTPEMFILE set the path to the PEM encoded SSL client certificates database file. If
set, a client certificate authentication is enabled.
CACERTIFICATEFILE set the path to the PEM encoded file containing Certificate Authority
(CA) certificates. Monit uses OpenSSL's default CA certificates if this options is not
used (openssl version -d can be used to get the default CA certificates). Many
distributions comes with SSL and CA certificates already setup and using this option is
normally not necessary.
CACERTIFICATEPATH set the path to the directory containing Certificate Authority (CA)
certificates. Monit uses OpenSSL's default CA certificates if this options is not used.
Many distributions comes with SSL and CA certificates already setup and using this option
is normally not necessary.
The SSL options statement will globally apply to all SSL/TLS connection made through
Monit. SSL options can also be set in a local check, in mailserver settings or in the
mmonit statement, and will then override or extend the global settings.
To set global SSL options, put this statement near the top of your .monitrc file:
set ssl options {...}
Here is an example of setting both global and local SSL options:
# Enable certificate verification for all SSL connections
# Self-signed certificates are not allowed by default
set ssl options {
verify: enable
}
# Verify certificate (via global setting)
# Allow self-signed certificate for this check
check host example with address example.com
if failed
port 443
protocol https
with ssl options {selfsigned: allow}
then alert
# Do not verify example2.com's certificate (override global setting)
check host example2 with address example2.com
if failed
port 443
protocol https
with ssl options {verify: disable}
then alert
FIPS MODE
To enable FIPS mode (provided your OpenSSL library supports it), add this statement to
Monit control file:
SET FIPS
MONIT HTTPD
If specified in the control file, Monit will start with HTTP support. You can then use
Monit CLI to start and stop services, disable or enable service monitoring as well as view
the status of each service.
If HTTP support is enabled over TCP rather than over a Unix Socket, you can also view
Monit's informative dashboard in your web browser.
Note that if HTTP support is disabled, the Monit CLI interface will have reduced
functionality, as most CLI commands (such as "monit status") needs to communicate with the
Monit background process via the HTTP interface. We strongly recommend having HTTP support
enabled. If security is a concern, bind the HTTP interface to local host only or use Unix
Socket so Monit is not accessible from the outside.
UNIX SOCKET
Syntax for Unix Socket:
SET HTTPD UNIXSOCKET <path>
[UID <uid | username>]
[GID <gid | groupname>]
[PERMISSION <octal number>]
ALLOW <user:password>+
Example:
set httpd unixsocket /var/run/monit.sock
allow username:password
UNIXSOCKET set the path to the Unix Socket Monit should bind to and listen on.
UID Socket owner (optional, defaults to the user who executes Monit)
GID Socket group (optional, defaults to primary group of the user who executes Monit)
PERMISSION Socket permissions - absolute octal mode (optional, process UMASK is applied by
default)
TCP PORT
Syntax for TCP port:
SET HTTPD PORT <number>
[ADDRESS <hostname | IP-address>]
[[with] SSL {pemfile: <path>}]
ALLOW <user:password | IP-address | IP-range>+
PORT set the port Monit should bind to and listen on. Monit is usually setup on port 2812.
Example:
set httpd port 2812
allow username:password
You can now use <http://localhost:2812/> to access Monit's web interface from a browser,
after you have entered username and password as credentials. You might need to use double
quotes around the password if it contains special chars such as "p@ssw:r#".
ADDRESS make Monit listen on a specific interface only. For example if you don't want to
expose Monit's web interface to the network, bind it to localhost only. Monit will accept
connections on any addresses if the ADDRESS option is not used:
set httpd
port 2812
use address 127.0.0.1
allow username:password
Monit HTTP over TCP supports both IP version 4 and 6. Support is transparent and does not
require any special configuration. If the bind address is not specified as in this
example:
set httpd
port 2812
allow ...
Monit will bind to and listen on port 2812 on all interfaces, both IPv4 and IPv6 if
available. To force Monit HTTP to only listen on and accept connections over IP version 6,
specify an IPv6 address:
set httpd
port 2812
use address "fe80::222:19ff:fe53:6c59"
allow ...
Likewise, to force Monit HTTP to only listen on and accept connections over IP version 4,
specify an IPv4 address:
set httpd
port 2812
use address 62.109.39.247
allow ...
SSL settings
SSL enable SSL/TLS for Monit's web interface. See options for full list of SSL options.
PEMFILE sets the path to the PEM encoded file, which contains the server's private key and
certificate. This file should be stored in a safe place on the filesystem and should have
strict permissions, no more than 0700.
As an alternative PEMCHAIN and PEMKEY sets the path to separate PEM encoded certificate
chain and private key file. The key file should be stored in a safe place on the
filesystem and should have strict permissions, no more than 0700.
Example for using pemfile:
set httpd
port 2812
with ssl {
pemfile: /etc/ssl/certs/monit.pem
}
allow myuser:mypassword
Example for using separate certificate chain and key:
set httpd
port 2812
with ssl {
pemchain: /etc/ssl/certs/monit.chain.pem
pemkey: /etc/ssl/certs/monit.key.pem
}
allow myuser:mypassword
You can now use <https://localhost:2812/> to access the Monit web server over a TLS
encrypted connection.
Self-signed server certificates note: The Monit CLI works on a client-server basis and
uses the Monit HTTP GUI to collect status from the Monit daemon and pass commands like
start/stop to it. As self-signed certificates are rejected by default for security
reasons, the CLI won't work unless you explicitly allow it by using the SELFSIGNED: ALLOW
option:
set httpd
port 2812
with ssl {
pemfile: /etc/ssl/certs/monit.pem
selfsigned: allow
}
allow myuser:mypassword
CLIENTPEMFILE enables a client certificate based authentication and sets the path to a PEM
encoded database file, that contains a list of allowed client certificates. A connecting
client has to provide a certificate known to Monit (listed in clientpemfile), otherwise it
is rejected. This file must also include all necessary CA certificates. By default self-
signed client certificates are rejected for security reasons, if you want to allow self-
signed client certificates (recommended only for testing), you have to allow it explicitly
using the SELFSIGNED: ALLOW option (see the example above). See your browser's
documentation for how to import client certificate to it.
Example:
set httpd
port 2812
with SSL {
pemfile: /etc/ssl/certs/monit.pem
clientpemfile: /etc/ssl/certs/monit-client.pem
}
Monit version signature
SIGNATURE can be used to hide Monit version from the HTTP response header and error pages.
For example:
set httpd
port 2812
signature disable
allow myuser:mypassword
Authentication
Access to the Monit web interface is controlled primarily via the ALLOW option which is
used to specify authentication and authorise only specific clients to connect.
If the Monit command line interface is being used, at least one cleartext password is
necessary (see below), otherwise the Monit command line interface will not be able to
connect to the Monit web interface.
Clients that try to connect to Monit, but submit a wrong username and/or password are
logged with their IP-address.
Client certificates
This authentication method is a strong authentication mechanism and employ HTTPS client
certificates to verify the authenticity of a connecting client. Clients must posses a
Public Key Certificate known by Monit. The client must connect to Monit over SSL and Monit
will ask the client to send its certificate. Upon receiving the certificate Monit compares
the certificate to certificates located in the CLIENTPEMFILE file. Access is granted if
the client certificate is in this file. See SSL settings for details.
Basic Authentication
Monit supports Basic Authentication as described in RFC 2617.
In short; a server challenge a client (e.g. a Browser) to send authentication information
(username and password) and if accepted, the server will allow the client access to the
requested document.
The biggest weakness with Basic Authentication is that username and password is sent in
clear-text over the network (i.e. base64 encoded). It is therefore recommended that you
do not use this authentication method unless you run Monit with ssl support. With ssl, it
is safe to use Basic Authentication since all HTTP data, including Basic Authentication
headers will be encrypted.
Cleartext user and password
Monit will use Basic Authentication if an allow statement contains a username and a
password separated with a single ':' character.
Note: Special characters can be used, but for non-alphanumerics the password has to be
quoted.
Syntax:
ALLOW <username>:<password>
Host and network allow list
Monit maintains an access-control list of hosts and networks allowed to connect. You can
add as many hosts as you want to, but only hosts with a valid domain name or its IP
address are allowed.
Monit will query a name server to check any hosts trying to connect. If a host (client) is
trying to connect, but cannot be found in the access list or cannot be resolved, Monit
will shutdown the connection to the client promptly.
Control file example:
set httpd port 2812
allow localhost
allow my.other.work.machine.com
allow 10.1.1.1
allow 192.168.1.0/255.255.255.0
allow 10.0.0.0/8
Clients, not mentioned in the allow list and trying to connect to Monit will be denied
access and are logged with their IP-address.
PAM
PAM is supported on platforms which provide PAM (such as Linux, macOS, FreeBSD, NetBSD).
Syntax:
ALLOW @<group>
where "group" is the group name allowed to access Monit's web interface. Monit uses a PAM
service called monit for PAM authentication, see the PAM manual page for detailed
instructions on how to set the PAM service and PAM authentication plugins.
Sample PAM service for Monit on macOS (store as "/etc/pam.d/monit" file):
# monit: auth account password session
#auth sufficient pam_securityserver.so
#auth sufficient pam_unix.so
auth sufficient pam_opendirectory.so
auth required pam_deny.so
account required pam_permit.so
password required pam_deny.so
session required pam_permit.so
And a similar PAM service for Monit on Linux (store as "/etc/pam.d/monit" file):
# monit: auth account password session
auth sufficient pam_unix2.so
auth required pam_deny.so
account required pam_permit.so
password required pam_deny.so
session required pam_permit.so
A "monitrc" config which only allows group "admin" and "staff" authenticated via PAM to
access the web interface:
set httpd
port 2812
allow @admin
allow @staff readonly
htpasswd file
Alternatively you store credentials in a "htpasswd" formatted file (one user:passwd entry
per line), like so: allow [cleartext|crypt|md5] /path [users]. The default is cleartext
passwords. In case passwords are digested it is necessary to specify the cryptographic
method. If you do not want all users in the password file to have access to Monit, you can
specify only those users that should have access in the allow statement. Otherwise all
users are added.
Example1:
set httpd port 2812
allow md5 /etc/httpd/htpasswd john paul ringo george
If you use this method together with a host list, then only clients from the listed hosts
will be allowed to connect to the Monit HTTP server and each client will be asked to
provide a username and a password.
Example2:
set httpd port 2812
allow localhost
allow 10.1.1.1
allow hauk:"passw@rd"
If you only want to use Basic Authentication, then just provide allow entries with
username and password or password files as in example 1 above.
Read-only users
Further it is possible to define some users as read-only. A read-only user can read the
Monit web pages but will not get access to push-buttons and cannot change a service from
the web interface.
set httpd port 2812
allow admin:password
allow hauk:password read-only
allow @admins
allow @users read-only
A user is set to read-only by using the read-only keyword after username:password. In the
above example the user hauk is defined as a read-only user, while the admin user has all
access rights.
Read-only http server
Finally is is possible to restrict the entire web interface as read-only. All users,
regardless if defined with or without the read-only keyword, have only the permissions
described above. When using this setting it is recommend to set up a UNIXSOCKET as well,
otherwise the monit CLI will not work.
set httpd
port 2812
read-only
unixsocket /run/monit.socket
allow @users
ALERT MESSAGES
Monit will raise an alert in the following situations:
o A service does not exist (e.g. process is not running)
o Cannot read service data (e.g. cannot get filesystem usage)
o Execution of a service related script failed (e.g. start failed)
o Invalid service type (e.g. if path points to directory instead of file)
o Custom test script returned error
o Ping test failed
o TCP/UDP connection and/or port test failed
o Resource usage test failed (e.g. cpu usage too high)
o Checksum mismatch or change (e.g. file changed)
o File size test failed (e.g. file too large)
o Timestamp test failed (e.g. file is older then expected)
o Permission test failed (e.g. file mode doesn't match)
o An UID test failed (e.g. file owned by different user)
o A GID test failed (e.g. file owned by different group)
o A process's PID changed out of Monit's control
o A process's PPID changed out of Monit control
o Too many service recovery attempts failed
o A file content test found a match
o Filesystem flags changed
o A service action was performed by administrator
o A network link down or up
o A network link capacity changed
o A network link saturation failed
o A network link upload/download rate failed
o Monit was started, stopped or reloaded
To get an alert via e-mail, set the alert target using the global "set alert" statement
(for all services) or the "alert" statement in the context of a service entry (for a
single service).
Setting an alert recipient
If an event occurs, Monit will send an alert. There are two kinds of alert statement:
global and local.
Global syntax:
SET ALERT mail-address [[NOT] {event, ...}] [REMINDER cycles]
Example:
set alert foo@bar
will send a default email to the address foo@bar whenever any event occurs on any service.
If you want to send alert messages to more email addresses, add a "set alert 'email'"
statement for each address.
It is also possible to use the local alert statement in the context of a service check to
enable alert for the given service only:
ALERT mail-address [[NOT] {event, ...}] [REMINDER cycles]
Local alert example:
check host myhost with address 1.2.3.4
if failed port 3306 protocol mysql then alert
if failed port 80 protocol http then alert
alert foo@baz # Local service alert
You can combine global and local alert statements. If there is a conflict, the local alert
has precedence and overrides the global statement.
Setting an event filter
If you only want an alert message sent for certain events, list them in an "{event, ...}"
block, e.g.:
set alert foo@bar only on { timeout, nonexist }
The event list can also be negated to send alerts for all events except those which are
listed, by prepending the list with the word "not". For example, to receive all alerts
except notification about Monit program start and stop:
set alert foo@bar but not on { instance }
Here is a list of all possible event types emitted by Monit. Values from the first column
can be used in the event filter list mentioned above:
Event: | Failure state: | Success state:
---------------------------------------------------------------------
action | "Action failed" | "Action done"
checksum | "Checksum failed" | "Checksum succeeded"
bytein | "Download bytes exceeded" | "Download bytes ok"
byteout | "Upload bytes exceeded" | "Upload bytes ok"
connection | "Connection failed" | "Connection succeeded"
content | "Content failed", | "Content succeeded"
data | "Data access error" | "Data access succeeded"
exec | "Execution failed" | "Execution succeeded"
fsflags | "Filesystem flags failed" | "Filesystem flags succeeded"
gid | "GID failed" | "GID succeeded"
icmp | "Ping failed" | "Ping succeeded"
instance | "Monit instance changed" | "Monit instance changed not"
invalid | "Invalid type" | "Type succeeded"
link | "Link down" | "Link up"
nonexist | "Does not exist" | "Exists"
packetin | "Download packets exceeded" | "Download packets ok"
packetout | "Upload packets exceeded" | "Upload packets ok"
permission | "Permission failed" | "Permission succeeded"
pid | "PID failed" | "PID succeeded"
ppid | "PPID failed" | "PPID succeeded"
resource | "Resource limit matched" | "Resource limit succeeded"
saturation | "Saturation exceeded" | "Saturation ok"
size | "Size failed" | "Size succeeded"
speed | "Speed failed" | "Speed ok"
status | "Status failed" | "Status succeeded"
timeout | "Timeout" | "Timeout recovery"
timestamp | "Timestamp failed" | "Timestamp succeeded"
uid | "UID failed" | "UID succeeded"
uptime | "Uptime failed" | "Uptime succeeded"
Each alert recipient can have it's own filter, for example:
set alert foo@bar { nonexist, timeout, resource, icmp, connection }
set alert security@bar on { checksum, permission, uid, gid }
set alert admin@bar
Setting an error reminder
Monit by default sends just one notification if a service failed and another when/if it
recovers. If you want to be notified that the service is still in a failed state, you can
use the reminder option in the alert statement:
SET ALERT mail-address [WITH] REMINDER [ON] number [CYCLES]
For example if you want to be notified each tenth cycle if a service remains in a failed
state, you can use:
alert foo@bar with reminder on 10 cycles
Likewise if you want to be notified on each failed cycle, you can use:
alert foo@bar with reminder on 1 cycle
Disabling alerts for some service
To suppress alerts for some user and service, add the "noalert" statement in the context
of a service check.
NOALERT mail-address
Example (send all alerts to foo@bar except for service p3):
set alert foo@bar
check process p1 with pidfile /var/run/p1.pid
check process p2 with pidfile /var/run/p2.pid
check process p3 with pidfile /var/run/p3.pid
noalert foo@bar
Message format
The alert message format can be modified by using the "set mail-format" statement:
SET MAIL-FORMAT {mail-format}
Example:
set mail-format {
from: Monit Support <monit@foo.bar>
reply-to: support@domain.com
subject: $SERVICE $EVENT at $DATE
message: Monit $ACTION $SERVICE at $DATE on $HOST: $DESCRIPTION.
Yours sincerely,
monit
}
The from: option is the sender's email address for Monit alerts. A sender's name is
optional, but if used, requires that the subsequent email-address is enclosed in angle
brackets as in the example above.
The reply-to: option can be used to set the reply-to mail header, optionally with a name.
The subject: option sets the message subject and must be on only one line.
The message: option sets the mail body. This option should always be the last in a mail-
format statement. The mail body can be as long as needed, but must not contain the block-
closing '}' character.
You need not use all options, only the option which you want to override. For example to
globally change the sender address only:
set mail-format { from: bofh@foo.bar }
The subject and body may contain $NAME variables, which are expanded by Monit. Here is a
list of variables that can be used when composing an alert message.
• $EVENT
A string describing the event that occurred.
• $SERVICE
The service name
• $DATE
The current time and date (RFC 822 date style).
• $HOST
The name of the host Monit is running on
• $ACTION
The name of the action which was done by Monit.
• $DESCRIPTION
The description of the error condition
Setting a mail server for alert delivery
The mail server Monit should use to send alert messages is defined with a "set mailserver"
statement:
SET MAILSERVER
<hostname|ip-address>
[PORT number]
[USERNAME string] [PASSWORD string]
[using SSL [with options {...}]
[CERTIFICATE CHECKSUM [MD5|SHA1] <hash>],
...
[with TIMEOUT X SECONDS]
[using HOSTNAME hostname]
Multiple mail servers can be set by using a comma separated list. If Monit cannot connect
to the first server, it will try the next in the list and so on.
The port statement allows one to override the default SMTP port (465 for SSL, or 25 for
TLS and non secure connection).
Monit supports AUTH PLAIN and AUTH LOGIN for SMTP authentication. You can set a username
and a password using the USERNAME and PASSWORD options.
You can set SSL/TLS options for the connection and also check a SSL certificate checksum.
The default connection timeout is 5 seconds. You can rise this limit using the TIMEOUT
option.
Example (setting two mail servers for failover):
set mailserver smtp.gmail.com, smtp.other.host
By default, Monit uses the local host name in SMTP HELO/EHLO and in the Message-ID header.
You can override this using the HOSTNAME option.
Event queue
If no mail server is available, Monit can queue events in the local file-system for retry
until the mail server recovers.
If Monit is used with M/Monit, the event queue provides a safe event store for M/Monit in
the case of temporary problems.
The event queue is persistent across Monit restarts and provided that the back-end
filesystem is persistent, across system restart as well.
By default, the queue is disabled and if the alert handler fails, Monit will simply drop
the alert message.
To enable the event queue, add the following statement:
SET EVENTQUEUE BASEDIR <path> [SLOTS <number>]
The <path> is the path to the directory where events will be stored.
Optionally if you want to limit the queue size, use the slots option to only store up to
number event messages.
Example:
set eventqueue basedir /var/monit slots 5000
If you are running more then one Monit instance on the same machine, you must use
separated event queue directories.
SERVICE METHODS
Each service can have associated start, stop and restart methods which Monit can use to
execute action on the service.
Syntax:
<START | STOP | RESTART> [PROGRAM] = "program"
[[AS] UID <number | string>]
[[AS] GID <number | string>]
[[WITH] TIMEOUT <number> SECOND(S)]
If the "program" is a shell script it must begin with "#!" and the remainder of the first
line must specify an interpreter for the program. e.g. "#!/bin/sh"
The "program" must also be executable (for example mode 0755).
It's possible to write scripts directly into the program this way:
stop = "/bin/sh -c 'kill -s SIGTERM `cat /var/run/process.pid`'"
By default the program is executed as the user under which Monit is running. If Monit is
running as root, you may optionally specify the UID and GID the executed program should
switch to.
Example:
check process mmonit with pidfile /usr/local/mmonit/mmonit/logs/mmonit.pid
start program = "/usr/local/mmonit/bin/mmonit" as uid "mmonit" and gid "mmonit"
stop program = "/usr/local/mmonit/bin/mmonit stop" as uid "mmonit" and gid "mmonit"
In the case of a process check, Monit will wait up to 30 seconds for the start/stop action
to finish before giving up and report an error. You can override this timeout using the
TIMEOUT option or globally using the set limits.
Example:
check process foobar with pidfile /var/run/foobar.pid
start program = "/etc/init.d/foobar start" with timeout 60 seconds
stop program = "/etc/init.d/foobar stop"
SERVICE POLL TIME
Services are checked regularly in an interval defined by the "set daemon n" statement.
Checks are performed in the same order as they are written in the ".monitrc" file, except
if dependencies are setup between services, where pre-requisite services are tested first.
It is possible to modify a service check schedule by using the "every" statement.
There are three variants:
1. A poll cycle multiple
EVERY [number] CYCLES
2. Cron-style
EVERY [cron]
3. Negative Cron-style (do-not-check)
NOT EVERY [cron]
A cron-style string consist of 5 fields separated with white-space. All fields are
required:
Name: | Allowed values: | Special characters:
---------------------------------------------------------------
Minutes | 0-59 | * - ,
Hours | 0-23 | * - ,
Day of month | 1-31 | * - ,
Month | 1-12 (1=jan, 12=dec) | * - ,
Day of week | 0-6 (0=sunday, 6=saturday) | * - ,
The special characters:
Character: | Description:
---------------------------------------------------------------
* (asterisk) | The asterisk indicates that the expression will
| match for all values of the field; e.g., using
| an asterisk in the 4th field (month) would
| indicate every month.
- (hyphen) | Hyphens are used to define ranges. For example,
| 8-9 in the hour field indicate between 8AM and
| 9AM. Note that range is from start time until and
| including end time. That is, from 8AM and until
| 10AM unless minutes are set. Another example,
| 1-5 in the weekday field, specify from monday to
| friday (including friday).
, (comma) | Comma are used to specify a sequence. For example
| 17,18 in the day field indicate the 17th and 18th
| day of the month. A sequence can also include
| ranges. For example, using 1-5,0 in the weekday
| field indicate monday to friday and sunday.
Example 1: Check once per two cycles
check process nginx with pidfile /var/run/nginx.pid
every 2 cycles
Example 2: Check every workday between 8AM to 7PM
check program checkOracleDatabase
with path /var/monit/programs/checkoracle.pl
every "* 8-19 * * 1-5"
Example 3: Do not run the check in the backup window on Sunday between 0AM to 3AM,
otherwise run the check with the regular poll cycle frequency.
check process mysqld with pidfile /var/run/mysqld.pid
not every "* 0-3 * * 0"
Limitations:
The current scheduler is poll cycle based. If a service check is scheduled with the every
cron statement, Monit will check if the current time match the cron-string pattern. If it
does, then the check is performed otherwise it is skipped. The cron specification does not
guarantee when exactly the test will run, this depends on the default poll time and the
length of the check cycle. In other words, we cannot guarantee that Monit will run on a
specific time. Therefore we strongly recommend to use an asterix in the minute field or at
minimum a range, e..g. 0-15. Never use a specific minute as Monit may not run on that
minute.
We will address this limitation in a future release and convert the scheduler from serial
polling into a parallel non-blocking scheduler where checks are guaranteed to run on time
and with seconds resolution.
SERVICE GROUPS
Service entries in the control file, monitrc, can be grouped together by the group
statement. The syntax is simply (keyword in capital):
GROUP groupname
With this statement it is possible to group similar service entries together and manage
them as a whole. Monit provides functions to start, stop, restart, monitor and unmonitor a
group of services, like so:
To start a group of services from the console:
monit -g <groupname> start
To stop a group of services:
monit -g <groupname> stop
To restart a group of services:
monit -g <groupname> restart
A service can be added to multiple groups by using more than one group statement:
group www
group filesystem
SERVICE MONITORING MODE
Monit supports two monitoring modes: active and passive.
Syntax:
MODE <ACTIVE | PASSIVE>
In active mode, Monit will pro-actively monitor a service and in case of problems raise
alerts and restart the service. Active is the default mode.
The passive mode is similar to the active mode, except if the service fails, monit will
not try to fix a problem by restarting the service and will raise alerts only.
SYSTEM REBOOT AND SERVICE STARTUP
Monit supports three reboot modes: start, nostart and laststate.
Syntax:
ONREBOOT <START | NOSTART | LASTSTATE>
In start mode, Monit will always start the service automatically on reboot, even if it was
stopped before restart. This is the default mode and used if onreboot is not specified.
In nostart mode, the service is never started automatically after reboot. This mode is
intended for a high-availability solutions with active/passive clusters. For example, a
service group HA, consisting of e.g. a mobile IP alias and an application server, is
started on host H1, host H2 is backup and heartbeat is in place between both hosts. The
service group HA must be started on one node only. If H1 dies, H2 takes over the HA group.
If H1 reboots, it is important that it won't try to start the HA group also. Even though
the group was active on H1 before it crashed, as HA is running on H2 now.
In laststate mode, a service's monitoring state is persistent across reboot. For instance,
if a service was started before reboot, it will be started after reboot. If it was stopped
before reboot, it will not be started after and so on.
The default ONREBOOT START mode can be overridden globally:
SET ONREBOOT <START | NOSTART | LASTSTATE>
SERVICE RESTART LIMIT
Monit provides a restart limit mechanism for situations where a service simply refuses to
start or respond over a longer period.
The restart limit mechanism is based on number of service restarts and number of poll-
cycles. For example, if a service had x restarts within y poll-cycles (where x <= y) then
Monit will perform an action (for example unmonitor the service). If a timeout occurs,
Monit will send an alert message if you have register interest for this event.
The syntax for the timeout statement is as follows (keywords are in capital):
IF <number> RESTART <number> CYCLE(S) THEN <action>
The action value is either one of common actions or TIMEOUT (for backward compatibility,
equals to UNMONITOR action).
Here is an example where Monit will unmonitor the service if it was restarted 2 times
within 3 cycles:
if 2 restarts within 3 cycles then unmonitor
To have Monit check the service again after monitoring was disabled, run "monit monitor
servicename" from the command line.
Example for setting custom exec on timeout:
if 5 restarts within 5 cycles then exec "/foo/bar"
Example for stopping the service:
if 7 restarts within 10 cycles then stop
SERVICE DEPENDENCIES
If specified in the control file, Monit can do dependency checking before start, stop,
monitoring or unmonitoring of services. The dependency statement may be used within any
service entries in the Monit control file.
The syntax for the depend statement is simply:
DEPENDS on service[, service [,...]]
Where service is a check service entry name used in your ".monitrc" file, for instance
apache or datafs.
You may add more than one service name of any type or use more than one depend statement
in an entry.
Services specified in a depend statement will be checked during
stop/start/monitor/unmonitor operations.
If a service is stopped or unmonitored it will stop/unmonitor any services that depends on
itself.
If the service is started, all services which this service depends on will be started
before starting this service. if start of some service failed, the service with
prerequisites will NOT be started and the, but will remember that it should start and will
retry next cycle.
If a service is restarted, it will first stop any active services that depend on it and
after it is started, start all depending services that were active before the restart
again.
Here is an example where we set up an apache service entry to depend on the underlying
apache binary. If the binary should change an alert is sent and apache is not monitored
anymore. The rationale is security and that Monit should not execute a possibly cracked
apache binary.
(1) check process apache with pidfile "/var/run/httpd.pid"
(2) depends on httpd
(3) ...
(4)
(5) check file httpd with path /usr/bin/httpd
(6) if failed checksum then stop
The first entry is the process entry for apache. The second line sets up a dependency
between this entry and the service entry named httpd in line 5. A dependency tree works as
follows, if an action is conducted in a lower branch it will propagate upward in the tree
and for every dependent entry execute the same action. In this case, if the checksum
should fail in line 6 then an stop action is executed and apache binary is not checked
anymore. But since the apache process entry depends on the httpd entry this entry will
also execute the stop action. In short, if the checksum test for the httpd binary file
should fail, both the check file httpd and the check process apache entry are stopped.
A dependency tree is a general construct and can be used between all types of service
entries and span many levels and propagate any supported action (except the exec action
which will not propagate upward in a dependency tree for obvious reasons).
Here is another different example. Consider the following common server setup:
WEB-SERVER -> APPLICATION-SERVER -> DATABASE -> FILESYSTEM
(a) (b) (c) (d)
You can set dependencies so that the web-server depends on the application server to run
before the web-server starts and the application server depends on the database server and
the database depends on the filesystem to be mounted before it starts. See also the
example section below for examples using the depend statement.
Here we describe how Monit will function with the above dependencies:
If no services are running
Monit will start the servers in the following order: d, c, b, a
If all servers are running
When you run 'monit stop all' this is the stop order: a, b, c, d. If you run 'Monit
stop d' then a, b and c are also stopped because they depend on d and finally d is
stopped.
If a does not run
Monit will start a
If b does not run
Monit will first stop a then start b and finally start a if b is up again.
If c does not run
Monit will first stop a and b then start c and finally start b then a.
If d does not run
Monit will first stop a, b and c then start d and finally start c, b then a.
If the control file contains a depend loop.
A depend loop is for example; a->b and b->a or a->b->c->a.
When Monit starts it will check for such loops and complain and exit if a loop was
found. It will also exit with a complaint if a depend statement was used that does not
point to a service in the control file.
SERVICE TESTS
LIMITS
You can configure and set various limits to tweak buffer sizes and timeouts used by Monit.
In most situations the default values are fine. If needed, below are the limits you can
currently modify in Monit.
Syntax:
SET LIMITS {
PROGRAMOUTPUT: <number> <unit>,
SENDEXPECTBUFFER: <number> <unit>,
FILECONTENTBUFFER: <number> <unit>,
HTTPCONTENTBUFFER: <number> <unit>,
NETWORKTIMEOUT: <number> <timeunit>
PROGRAMTIMEOUT: <number> <timeunit>
STOPTIMEOUT: <number> <timeunit>
STARTTIMEOUT: <number> <timeunit>
RESTARTTIMEOUT: <number> <timeunit>
EXECTIMEOUT: <number> <timeunit>
}
Where:
unit is "B" (byte), "kB" (kilobyte) or "MB" (megabyte)
timeunit is "MS" (millisecond) or "S" (second)
Options legend:
----------------------------------------------------------------------------------
| Option | Description | Default |
----------------------------------------------------------------------------------
| programOutput | limit for check program output (truncated after) | 512 B |
| sendExpectBuffer | limit for send/expect protocol test | 256 B |
| fileContentBuffer | limit for file content test (line) | 512 B |
| httpContentBuffer | limit for HTTP content test (response body) | 1 MB |
| networkTimeout | timeout for network I/O | 5 s |
| programTimeout | timeout for check program | 300 s |
| stopTimeout | timeout for service stop | 30 s |
| startTimeout | timeout for service start | 30 s |
| restartTimeout | timeout for service restart | 30 s |
| execTimeout | timeout for test action exec | nolimit |
----------------------------------------------------------------------------------
GENERAL SYNTAX
Monit offers several if-tests you can use in a 'check' statement to test various aspects
of a service.
You can test both for a predefined value or for a range and take actions if the value
changes.
General syntax for testing a specific value or range:
IF <test> THEN <action> [ELSE <action>]
The action is evaluated each time the <TEST> condition is true. Success action is optional
and executed only when the state changes from failure to success. If success action is not
set, Monit will send a recovery alert by default.
General syntax for a value change test:
IF CHANGED <test> THEN <action>
The action is executed each time the value changes. Monit will remember the new value and
will trigger event if the value change again.
ACTION
Each test can have associated alert, start, stop, restart, unmonitor or exec methods which
Monit can use to execute actions or programs on the service. The success action also
supports the ignore method.
Syntax:
ALERT | IGNORE | START | STOP | RESTART | UNMONITOR
or:
EXEC "program"
[[AS] UID <number | string>]
[[AS] GID <number | string>]
[[WITH] TIMEOUT <number> SECOND(S)]
[REPEAT EVERY [<number>] CYCLE(S)]
In each test you must select the action to be executed from this list:
• ALERT sends the user an alert event on each state change.
• RESTART restarts the service and send an alert. Restart is performed by calling the
service's registered restart method or by first calling the stop method followed by
the start method if restart is not set.
• START starts the service by calling the service's registered start method and send an
alert.
• STOP stops the service by calling the service's registered stop method and send an
alert. If Monit stops a service it will not be checked by Monit anymore nor restarted
again later. To reactivate monitoring of the service again you must explicitly enable
monitoring from the web interface or from the console.
• EXEC can be used to execute an arbitrary program and send an alert. If you choose this
action you must state the program to be executed and if the program requires arguments
you must enclose the program and its arguments in a quoted string. You may optionally
specify the uid and gid the executed program should switch to upon start. The program
is executed only once if the test fails. You can enable execute repetition if the
error persists for a given number of cycles. For instance:
if failed <test> then exec "/usr/local/bin/sms.sh"
as uid "nobody" and gid "nobody"
repeat every 5 cycles
Remember, if Monit is run by root, then all programs executed by Monit will be started
with superuser privileges unless the uid and gid extension is used.
• UNMONITOR will disable monitoring of the service and send an alert. The service will
not be checked by Monit anymore nor restarted again later. To reactivate monitoring
of the service you must explicitly enable monitoring from the web interface or from
the console.
• IGNORE can be used in the action to not generate an alert once the check reenters the
state.
FAULT TOLERANCE
By default an action is executed if it matches and the corresponding service is set in an
error state. However, you can require a test to fail more than once before the error event
is triggered and the service state is changed to failed. This is useful to avoid getting
alerts on spurious errors, which can happen, especially with network tests.
Syntax:
FOR <X> CYCLES ...
or:
<X> [TIMES WITHIN] <Y> CYCLES ...
The condition can be used both for failure and success action.
The first, simpler and recommended format requires "X" consecutive events before switching
the state:
if failed
port 80
for 3 cycles
then alert
The second format is more advanced and allows one to tolerate intermittent issues, but
still catch excessive problems, where the service is flapping between error and success
states frequently.
For example if every second cycle fails (1-0-1-0-1-0-...), then "for 2 cycles" condition
will never match, despite the service having problems. The following statement will catch
such a state:
if failed
port 80
for 3 times within 5 cycles
then alert
Example which sets multiple error levels and actions:
check filesystem rootfs with path /dev/hda1
if space usage > 80% for 5 times within 15 cycles then alert
if space usage > 90% for 5 cycles then exec '/try/to/free/the/space'
Note: the maximum value for cycles is 64.
EXISTENCE TESTS
This test allows one to trigger an action based on the monitored object existence. It is
supported for process, file, directory, filesystem and fifo services.
If no existence test is defined, the implicit non-existence test with restart action is
activated, so for example if the process stops, Monit will restart it.
There are two types of existence tests:
NON-EXIST
This test will trigger an action if the object does not exist. It can be used for example
to make sure apache is running, data filesystem is mounted, etc.
IF [DOES] NOT EXIST THEN <action>
action is a choice of "ALERT", "RESTART", "START", "STOP", "EXEC" or "UNMONITOR".
Example: Exec a script if a filesystem does NOT exist:
check filesystem disk1 with path /dev/sda1
if does not exist then exec "/sbin/mount..."
EXIST
This test is the inverse of the non-existence test: it will trigger an action if the
object DOES exist. It can be used for example to kill a process which shouldn't be
running.
IF [DOES] EXIST THEN <action>
action is a choice of "ALERT", "RESTART", "START", "STOP", "EXEC" or "UNMONITOR".
Example: kill a process that should not run:
check process vmware matching "vmware"
if exist then exec "/usr/bin/pkill -9 vmware"
Example: Alert if a file exist which shouldn't
check file x with path /some/path/x
if exist then alert
RESOURCE TESTS
Monit can examine how much resources a service is using. This test can only be used within
a system or process service entry in the Monit control file.
Depending on system or process characteristics, services can be stopped or restarted and
alerts can be generated. Thus it is possible to utilise systems which are idle and to
spare system under high load.
Syntax:
IF <resource> <operator> <value> THEN <action>
operator is a choice of "<", ">", "!=", "==" in C notation, "gt", "lt", "eq", "ne" in
shell sh notation and "greater", "less", "equal", "notequal" in human readable form (if
not specified, default is EQUAL).
value is either an integer or a real number.
action is a choice of "ALERT", "RESTART", "START", "STOP", "EXEC" or "UNMONITOR".
resource set depends on the service type:
System resource tests
LOADAVG([1min|5min|15min]) [PER CORE] refers to the system's load average. The load
average is the number of processes in the system run queue per CPU core, averaged over the
specified time period. Example:
if loadavg (1min) per core > 2 for 15 cycles then alert
if loadavg (5min) per core > 1.5 for 10 cycles then alert
if loadavg (15min) per core > 1 for 8 cycles then alert
If you'll omit the per core option, the test will check the total load average regardless
of CPU cores count.
CPU([user|system|wait|nice|hardirq|softirq|steal|guest|guestnice]) is the percent of time
the system spend in given type of task:
user
The CPU is running code in user space mode, which includes any process that doesn't
belong to the kernel, such as webservers, databases, shells and desktop related
programs.
system
The CPU is running the kernel, which includes drivers and other kernel modules. The
kernel also handles requests from user space processes like memory allocation, disk
and network I/O and creating child processes.
wait
I/O wait is when the CPU was idle while waiting for an I/O operation from disk or
network to complete.
nice
The nice statistics accounts for user space processes that are running with altered
priority (higher or lower then normal).
hardirq
The kernel is servicing hardware interrupt requests. Hardware interrupts come from
peripherals like keyboard, network interfaces, disks, system clock, etc.
softirq
The kernel is servicing software interrupt requests. Software interrupts come from
processes running in the system.
steal
This applies only to virtual machines on a hypervisor. The steal time shows the
percentage of time a virtual machine had to wait the real CPU while the hypervisor was
servicing another virtual machine. If this number remains high, the host system is too
busy and may need more physical CPUs or offload some virtual machines to another host.
guest
This applies only to host machines running a hypervisor. It shows time spent running a
virtual CPU for guest operating systems under the control of the Linux kernel. This
value is already included in "user" statistics.
guestnice
This applies only to host machines running a hypervisor. It shows time spent running a
virtual CPU for guest operating systems under the control of the Linux kernel, with
altered priority. This value is already included in "nice" statistics.
The user/system/wait/nice/hardirq/softirq/steal/guest/guestnice modifier is optional and
the support depends on platform (Linux support depends on kernel version, all statistics
are available since kernel 2.6.33):
-----------------------------------------------------------------------------------------------
| Platform | user | nice | system | wait | hardirq | softirq | steal | guest | guest nice |
-----------------------------------------------------------------------------------------------
| AIX | X | | X | X | | | | | |
| DragonFlyBSD | X | X | X | | X | | | | |
| FreeBSD | X | X | X | | X | | | | |
| Linux | X | X | X | X | X | X | X | X | X |
| MacOS | X | X | X | | | | | | |
| NetBSD | X | X | X | | X | | | | |
| OpenBSD | X | X | X | | X | | | | |
| Solaris | X | | X | X | | | | | |
-----------------------------------------------------------------------------------------------
Example:
if cpu usage > 95% for 10 cycles then alert
MEMORY is the system memory usage [%] or absolute value [B, kB, MB, GB]. Example:
if memory usage > 75% for 5 cycles then alert
SWAP is the swap usage of the system [%] or absolute [B, kB, MB, GB]. Example:
if swap usage > 20% for 10 cycles then alert
Process resource tests
CPU is the CPU usage of the process itself [%]. Monit calculates the CPU usage based on
number of threads vs. available CPU cores. If the process has one thread, the 100% CPU
usage equals to 100% utilization of one CPU core. If it has 2 threads, 100% CPU usage is
reported when it uses 2 CPU cores on 100%, etc. If the process has more threads then the
machine's available CPU cores, then the 100% CPU usage corresponds to utilization of all
available CPU cores. Example:
if cpu > 10% for 5 cycles then restart
TOTAL CPU is the total CPU usage of the process and its children in (percent). You will
want to use TOTAL CPU typically for services like Apache web server where one master
process forks child processes as workers. Example:
if total cpu > 50% for 10 cycles then restart
THREADS is the number of processes' threads. Example:
if threads > 3 then alert
CHILDREN is the number of child processes of the process. Example:
if children > 10 then alert
MEMORY is the memory usage of the process itself, [%] or absolute value [B, kB, MB, GB].
Example:
if memory usage > 8 MB then alert
TOTAL MEMORY is the memory usage of the process and its child processes in either percent
or as an amount [B, kB, MB, GB]. Example:
if total memory usage > 1% for 10 cycles then alert
PROCESS I/O ACTIVITY TEST
Monit can test process's filesystem read and write activity. This test can only be used in
the context of a process service type. Monit will normally need to run as the root user to
access this metrics.
The OS usually supports the per-process I/O metrics by bytes or by operations.
Some platforms allows one to differentiate the I/O subset that required physical storage
access from generic I/O which was handled by cache. Note that as the physical I/O is
usually aligned to the filesystem page, there may be difference between the total and
physical I/O even if the process tried to read just 1 byte.
Per-process I/O activity statistics by platform:
---------------------------------------------------------------
| Platform | Operation | Byte (physical) | Byte (generic) |
---------------------------------------------------------------
| AIX | X | | |
| DragonFlyBSD | X | | |
| FreeBSD | X | | |
| Linux | X | X | X |
| MacOS | | X | |
| NetBSD | X | | |
| OpenBSD | X | | |
| Solaris | X | | |
---------------------------------------------------------------
Read: bytes per second (generic)
Syntax:
IF READ [ACTIVITY] <operator> <number> <unit>/S THEN action
operator is a choice of "<",">","!=","==" in c notation, "gt", "lt", "eq", "ne" in shell
sh notation and "greater", "less", "equal", "notequal" in human readable form (if not
specified, default is EQUAL).
unit is a choice of "B","KB","MB","GB" or long alternatives "byte", "kilobyte",
"megabyte", "gigabyte", "percent".
action is a choice of "ALERT", "RESTART", "START", "STOP", "EXEC" or "UNMONITOR".
Example:
check process p...
if read activity > 1 MB/s then alert
Read: bytes per second (physical storage)
Syntax:
IF DISK READ [ACTIVITY] <operator> <number> <unit>/S THEN action
operator is a choice of "<",">","!=","==" in c notation, "gt", "lt", "eq", "ne" in shell
sh notation and "greater", "less", "equal", "notequal" in human readable form (if not
specified, default is EQUAL).
unit is a choice of "B","KB","MB","GB" or long alternatives "byte", "kilobyte",
"megabyte", "gigabyte", "percent".
action is a choice of "ALERT", "RESTART", "START", "STOP", "EXEC" or "UNMONITOR".
Example:
check process p...
if disk read activity > 1 MB/s then alert
Read: operations per second
Syntax:
IF DISK READ [ACTIVITY] <operator> <number> operations/S THEN action
operator is a choice of "<",">","!=","==" in c notation, "gt", "lt", "eq", "ne" in shell
sh notation and "greater", "less", "equal", "notequal" in human readable form (if not
specified, default is EQUAL).
action is a choice of "ALERT", "RESTART", "START", "STOP", "EXEC" or "UNMONITOR".
Example:
check process p...
if disk read activity > 500 operations/s then alert
Write: bytes per second (generic)
Syntax:
IF WRITE [ACTIVITY] <operator> <number> <unit>/S THEN action
operator is a choice of "<",">","!=","==" in c notation, "gt", "lt", "eq", "ne" in shell
sh notation and "greater", "less", "equal", "notequal" in human readable form (if not
specified, default is EQUAL).
unit is a choice of "B","KB","MB","GB" or long alternatives "byte", "kilobyte",
"megabyte", "gigabyte", "percent".
action is a choice of "ALERT", "RESTART", "START", "STOP", "EXEC" or "UNMONITOR".
Example:
check process p...
if write activity > 1 MB/s then alert
Write: bytes per second (physical storage)
Syntax:
IF DISK WRITE [ACTIVITY] <operator> <number> <unit>/S THEN action
operator is a choice of "<",">","!=","==" in c notation, "gt", "lt", "eq", "ne" in shell
sh notation and "greater", "less", "equal", "notequal" in human readable form (if not
specified, default is EQUAL).
unit is a choice of "B","KB","MB","GB" or long alternatives "byte", "kilobyte",
"megabyte", "gigabyte", "percent".
action is a choice of "ALERT", "RESTART", "START", "STOP", "EXEC" or "UNMONITOR".
Example:
check process p...
if disk write activity > 1 MB/s then alert
Write: operations per second
Syntax:
IF DISK WRITE [ACTIVITY] <operator> <number> operations/S THEN action
operator is a choice of "<",">","!=","==" in c notation, "gt", "lt", "eq", "ne" in shell
sh notation and "greater", "less", "equal", "notequal" in human readable form (if not
specified, default is EQUAL).
action is a choice of "ALERT", "RESTART", "START", "STOP", "EXEC" or "UNMONITOR".
Example:
check process p...
if disk write activity > 500 operations/s then alert
FILE CHECKSUM TEST
The checksum statement may only be used in a file service entry and can be used to check
the file's MD5 or SHA1 checksum.
Check specific checksum:
IF FAILED [MD5|SHA1] CHECKSUM [EXPECT checksum] THEN action
Check any file changes:
IF CHANGED [MD5|SHA1] CHECKSUM THEN action
The choice of MD5 or SHA1 is optional. MD5 features a 128 bits checksum (32 bytes hex
encoded string) and SHA1 a 160 bits checksum (40 bytes hex encoded string). If this option
is omitted, Monit will try to guess the method from the EXPECT string or use MD5 as the
default checksum.
"expect" is optional and if used, specifies the md5 or sha1 string Monit should expect
when testing a file's checksum. Monit will then not compute an initial checksum for the
file, but instead use the string you submit. For example:
if failed
checksum expect 8f7f419955cefa0b33a2ba316cba3659
then alert
You can, for example, use the GNU utility md5sum(1) or sha1sum(1) to create a checksum
string for a file and use this string in the expect-statement.
Reloading a server if its configuration file was changed:
check file apache_conf with path /etc/apache/httpd.conf
if changed checksum then exec "/usr/bin/apachectl graceful"
action is a choice of "ALERT", "RESTART", "START", "STOP", "EXEC" or "UNMONITOR".
TIMESTAMP TEST
The timestamp statement may only be used in a file, fifo or directory service entry.
Relative timestamp syntax:
IF <ACCESS TIME | ATIME | MODIFICATION TIME | MTIME | CHANGE TIME | CTIME | TIME[STAMP]> <operator> <value> [unit] THEN <action>
Timestamp change syntax:
IF CHANGED <ACCESS TIME | ATIME | MODIFICATION TIME | MTIME | CHANGE TIME | CTIME | TIME[STAMP]> THEN action
There are four timestamp test types:
ACCESS (ATIME)
Test the timestamp which is updated whenever the object is accessed, for
example the file is read. Filesystem usually allows one to disable atime
updates using mount options, so this test will work only if the filesystem
performs atime updates.
CHANGE (CTIME)
Test the timestamp which is updated whenever the object metadata such as
owner, group, permissions or hard link count are changed.
MODIFICATION (MTIME)
Test the timestamp which is updated whenever the object content is modified.
The file modification timestamp is updated whenever the file is truncated or
written to. The directory modification timestamp is updated whenever some
files/subdirectories were added to the directory or removed from that
directory.
DEFAULT (LATEST OF CHANGE AND MODIFICATION TIMES)
If no specific timestamp type is set, the latest of change and modification
timestamps is checked. This test allows for simple testing of any object
modification (data and metadata).
operator is a choice of "<", ">", "!=", "==" in C notation, "GT", "LT", "EQ", "NE" in
shell sh notation and "NEWER, "OLDER", "GREATER", "LESS", "EQUAL", "NOTEQUAL" in human
readable form (if not specified, default is EQUAL).
value is a time watermark.
unit is either "SECOND(S)", "MINUTE(S)", "HOUR(S)" or "DAY(S)".
action is a choice of "ALERT", "RESTART", "START", "STOP", "EXEC" or "UNMONITOR".
For example to reload apache if the configuration file changed:
check file apache_conf with path /etc/apache/httpd.conf
if changed timestamp then exec "/usr/bin/apachectl graceful"
For example to test directory for file addition or removal:
check directory bar path /foo/bar
if changed timestamp then alert
Example for sending alert if a log file is not updated for more than 1 hour:
if timestamp is older than 1 hour then alert
FILE SIZE TEST
The size statement may only be used in a check file service entry. If specified in the
control file, Monit will compute a size for a file.
Testing specific size or range:
IF SIZE [[operator] value [unit]] THEN action
Testing size changes:
IF CHANGED SIZE THEN action
operator is a choice of "<", ">", "!=", "==" in C notation, "GT", "LT", "EQ", "NE" in
shell sh notation and "GREATER", "LESS", "EQUAL", "NOTEQUAL" in human readable form (if
not specified, default is EQUAL).
value is a size watermark.
unit is a choice of "B","KB","MB","GB" or long alternatives "byte", "kilobyte",
"megabyte", "gigabyte". If it is not specified, "byte" unit is assumed by default.
action is a choice of "ALERT", "RESTART", "START", "STOP", "EXEC" or "UNMONITOR".
For example to send an alert if the file is too large:
check file mydb with path /data/mydatabase.db
if size > 1 GB then alert
FILE CONTENT TEST
The content statement can be used to incrementally test the content of a text file by
using regular expressions.
Syntax:
IF CONTENT <operator> <regex|path> THEN action
operator is either a "=" for match or "!=" for no-match.
regex is a string containing the extended regular expression. See also regex(7).
path is an absolute path to a file containing extended regular expression on every line.
See also regex(7).
action is a choice of "ALERT", "RESTART", "START", "STOP", "EXEC" or "UNMONITOR".
On startup the read position is set to the end of the file and Monit continues to scan to
the end of the file on each cycle.
If the file size should decrease or inode changed, the read position is set to the start
of the file.
Only lines ending with a newline character are inspected.
By default only the first 511 characters of a line are inspected. You can increase the
limit using the set limits statement.
IGNORE CONTENT <operator> <regex|path>
Lines matching an IGNORE are not inspected during later evaluations. IGNORE CONTENT has
always precedence over IF CONTENT.
All IGNORE CONTENT statements are evaluated first, in the order of their appearance.
Thereafter, all the IF CONTENT statements are evaluated.
For example:
check file syslog with path /var/log/syslog
ignore content = "monit"
if content = "^mrcoffee" then alert
FILESYSTEM MOUNT FLAGS TEST
Monit can test the filesystem mount flags for changes. This test is implicit and Monit
will send alert in case of failure by default.
This test is useful for detecting changes of filesystem flags such as if the filesystem
become read-only (on disk error) or mount flags were changed (such as nosuid).
The syntax for the fsflags statement is:
IF CHANGED FSFLAGS THEN action
action is a choice of "ALERT", "RESTART", "START", "STOP", "EXEC" or "UNMONITOR".
Example:
check filesystem rootfs with path /
if changed fsflags then exec "/my/script"
SPACE USAGE TEST
Monit can test a filesystem or a disk for space usage. This test may only be used in the
context of a filesystem service type.
Filesystems usually have some space reserved for the root user (ca. 1-5%), so non-
superusers cannot write to a nearly full filesystem. If you set a limit for the filesystem
which is used by non-root users you might want to consider these reserved blocks when
setting the limit. You can use Monit itself to view the reserved blocks percentage by
using the CLI status command or the HTTP interface for the given filesystem.
Syntax:
IF SPACE operator value unit THEN action
or:
IF SPACE FREE operator value unit THEN action
operator is a choice of "<",">","!=","==" in c notation, "gt", "lt", "eq", "ne" in shell
sh notation and "greater", "less", "equal", "notequal" in human readable form (if not
specified, default is EQUAL).
unit is a choice of "B","KB","MB","GB", "%" or long alternatives "byte", "kilobyte",
"megabyte", "gigabyte", "percent".
action is a choice of "ALERT", "RESTART", "START", "STOP", "EXEC" or "UNMONITOR".
Example:
check filesystem rootfs with path /
if space usage > 90% then alert
INODE USAGE TEST
Monit can test filesystem inode usage. This test may only be used in the context of a
filesystem service type.
Syntax:
IF INODE(S) operator value [unit] THEN action
or:
IF INODE(S) FREE operator value [unit] THEN action
operator is a choice of "<",">","!=","==" in c notation, "gt", "lt", "eq", "ne" in shell
sh notation and "greater", "less", "equal", "notequal" in human readable form (if not
specified, default is EQUAL).
unit is optional. If not specified, the value is an absolute count of inodes. You can use
the "%" character or the longer alternative "percent" as a unit.
action is a choice of "ALERT", "RESTART", "START", "STOP", "EXEC" or "UNMONITOR".
Example:
check filesystem rootfs with path /
if inode usage > 90% then alert
DISK I/O TEST
Monit can test a filesystem read and write activity. This test may only be used in the
context of a filesystem service type.
The available I/O metrics depends on the platform and filesystem. Some platforms allows us
to get I/O activity for specific partition, others just for the whole disk. Some allows us
to get metrics for network filesystems, others just for block devices.
Platforms I/O metrics granularity and filesystem support in Monit:
---------------------------------------------------------------------------------------
| Platform | Granularity | Supported filesystems | TBD |
---------------------------------------------------------------------------------------
| AIX | per-disk | Disk io monitoring currently not supported | JFSx |
| DragonFlyBSD | per-disk | UFS | HAMMER |
| FreeBSD | per-disk | UFS, ZFS | |
| Linux | per-filesystem | EXTx, XFS, BTRFS, ZFS, NFS, CIFS | |
| MacOS | per-disk | HFS | |
| NetBSD | per-disk | FFS | NFS |
| OpenBSD | per-disk | FFS | |
| Solaris | per-filesystem | ZFS, UFS, NFS | |
---------------------------------------------------------------------------------------
Read: bytes per second
Syntax:
IF READ [RATE] <operator> <number> <unit>/S THEN action
operator is a choice of "<",">","!=","==" in c notation, "gt", "lt", "eq", "ne" in shell
sh notation and "greater", "less", "equal", "notequal" in human readable form (if not
specified, default is EQUAL).
unit is a choice of "B","KB","MB","GB" or long alternatives "byte", "kilobyte",
"megabyte", "gigabyte", "percent".
action is a choice of "ALERT", "RESTART", "START", "STOP", "EXEC" or "UNMONITOR".
Example:
check filesystem disk1...
if read rate > 1 MB/s then alert
Read: operations per second
Syntax:
IF READ [RATE] <operator> <number> operations/S THEN action
operator is a choice of "<",">","!=","==" in c notation, "gt", "lt", "eq", "ne" in shell
sh notation and "greater", "less", "equal", "notequal" in human readable form (if not
specified, default is EQUAL).
action is a choice of "ALERT", "RESTART", "START", "STOP", "EXEC" or "UNMONITOR".
Example:
check filesystem disk1...
if read rate > 500 operations/s then alert
Write: bytes per second
Syntax:
IF WRITE [RATE] <operator> <number> <unit>/S THEN action
operator is a choice of "<",">","!=","==" in c notation, "gt", "lt", "eq", "ne" in shell
sh notation and "greater", "less", "equal", "notequal" in human readable form (if not
specified, default is EQUAL).
unit is a choice of "B","KB","MB","GB" or long alternatives "byte", "kilobyte",
"megabyte", "gigabyte", "percent".
action is a choice of "ALERT", "RESTART", "START", "STOP", "EXEC" or "UNMONITOR".
Example:
check filesystem disk1...
if write rate > 1 MB/s then alert
Write: operations per second
Syntax:
IF WRITE [RATE] <operator> <number> operations/S THEN action
operator is a choice of "<",">","!=","==" in c notation, "gt", "lt", "eq", "ne" in shell
sh notation and "greater", "less", "equal", "notequal" in human readable form (if not
specified, default is EQUAL).
action is a choice of "ALERT", "RESTART", "START", "STOP", "EXEC" or "UNMONITOR".
Example:
check filesystem disk1...
if write rate > 500 operations/s then alert
Service time per operation
Service Time is the time taken to complete a read or a write operation. This is a fairly
important metric. If it grows, it means that the disk is not able to handle the operations
fast enough. Growth charts are available in M/Monit.
Syntax:
IF SERVICE TIME <operator> <number> <unit> THEN action
operator is a choice of "<",">","!=","==" in c notation, "gt", "lt", "eq", "ne" in shell
sh notation and "greater", "less", "equal", "notequal" in human readable form (if not
specified, default is EQUAL).
unit is "MS" (millisecond) or "S" (second)
action is a choice of "ALERT", "RESTART", "START", "STOP", "EXEC" or "UNMONITOR".
Example:
if service time > 10 milliseconds
for 3 times within 5 cycles
then alert
PERMISSION TEST
Monit can test the permissions of file objects. This test may only be used in the context
of a file, fifo, directory or filesystem service types.
Syntax for testing specific permissions:
IF FAILED PERM(ISSION) octalnumber THEN action
Syntax for testing any permission change:
IF CHANGED PERM(ISSION) THEN action
octalnumber defines permissions for a file, a directory or a filesystem as four octal
digits (0-7). Valid range is 0000 - 7777 (you can omit the leading zeros, Monit will add
the zeros to the left. For example, "640" is a valid value and matches "0640").
action is a choice of "ALERT", "RESTART", "START", "STOP", "EXEC" or "UNMONITOR".
Example:
check file shadow with path /etc/shadow
if failed permission 0640 then alert
UID TEST
Monit can monitor the owner user id (uid) of a file, fifo, directory or owner and
effective user of a process.
Syntax:
IF FAILED [E]UID <value> THEN action
value defines a user id either in numeric or in string form.
action is a choice of "ALERT", "RESTART", "START", "STOP", "EXEC" or "UNMONITOR".
Example:
check file shadow with path /etc/shadow
if failed uid "root" then alert
GID TEST
Monit can monitor the owner group id (gid) of a file, fifo, directory or process.
Syntax:
IF FAILED GID <value> THEN action
value defines a group id either in numeric or in string form.
action is a choice of "ALERT", "RESTART", "START", "STOP", "EXEC" or "UNMONITOR".
Example:
check file shadow with path /etc/shadow
if failed gid "shadow" then alert
HARDLINK TEST
The hardlink statement may be used in a check file, fifo or directory service entry. If
specified in the control file, Monit will compute the number of hard links for a file,
fifo or directory.
Testing a specific value:
IF HARDLINK [[operator] value] THEN action
Testing hardlink changes:
IF CHANGED HARDLINK THEN action
operator is a choice of "<", ">", "!=", "==" in C notation, "GT", "LT", "EQ", "NE" in
shell sh notation and "GREATER", "LESS", "EQUAL", "NOTEQUAL" in human readable form (if
not specified, default is EQUAL).
value is a watermark.
action is a choice of "ALERT", "RESTART", "START", "STOP", "EXEC" or "UNMONITOR".
For example to send an alert if the number of used hard links of a directory is too large:
check directory upload with path /data/upload
if hardlink > 32000 then alert
PID TEST
Monit can test the process's PID. Monit will send an alert in case the PID changed outside
of Monit's control.
Syntax:
IF CHANGED PID THEN action
action is a choice of "ALERT", "RESTART", "START", "STOP", "EXEC" or "UNMONITOR".
This test is useful to detect possible process restarts which has occurred in the
timeframe between two Monit testing cycles.
For example if someone changes sshd configuration and did sshd restart outside of Monit's
control you will be notified that the process was replaced by a new instance:
check process sshd with pidfile /var/run/sshd.pid
if changed pid then alert
PPID TEST
Monit can test the process's parent PID (PPID) for changes. Monit will send alert in the
case that the PPID changed outside of Monit control.
The syntax for the ppid statement is:
IF CHANGED PPID THEN action
action is a choice of "ALERT", "RESTART", "START", "STOP", "EXEC" or "UNMONITOR".
Example:
check process myproc with pidfile /var/run/myproc.pid
if changed ppid then exec "/my/script"
UPTIME TEST
The uptime statement may only be used in a process and system service type context.
Syntax:
IF UPTIME [[operator] value [unit]] THEN action
operator is a choice of "<", ">", "!=", "==" in C notation, "GT", "LT", "EQ", "NE" in
shell sh notation and "GREATER", "LESS", "EQUAL", "NOTEQUAL" in human readable form (if
not specified, default is EQUAL).
value is a uptime watermark.
unit is either "SECOND", "MINUTE", "HOUR" or "DAY" (it is also possible to use "SECONDS",
"MINUTES", "HOURS", or "DAYS").
action is a choice of "ALERT", "RESTART", "START", "STOP", "EXEC" or "UNMONITOR".
Example of restarting the process every three days:
check process myapp with pidfile /var/run/myapp.pid
start program = "/etc/init.d/myapp start"
stop program = "/etc/init.d/myapp stop"
if uptime > 3 days then restart
SECURITY ATTRIBUTE TEST
The security attribute statement may only be used in a process context.
Syntax:
IF FAILED SECURITY ATTRIBUTE <string> THEN <action>
string expected security attribute value
action is a choice of "ALERT", "RESTART", "START", "STOP", "EXEC" or "UNMONITOR".
Example for SELinux:
check process ntpd matching "ntpd"
if failed security attribute "system_u:system_r:ntpd_t:s0" then alert
Example for AppArmor:
check process ntpd matching "ntpd"
if failed security attribute "/usr/sbin/ntpd (enforce)" then alert
SYSTEM AND PER-PROCESS FILEDESCRIPTORS TEST
Monit can test the filedescriptors usage on the system and process level. You can check
either an absolute value or percentual usage of the current maximum. The per-process
percentual usage can be used only if the system exposes per-process maximum.
Syntax:
IF FILEDESCRIPTORS <operator> <number> [%] THEN action
For process only, you can also check accumulated number for the process and all its
children.
Syntax:
IF TOTAL FILEDESCRIPTORS <operator> <number> THEN action
operator is a choice of "<",">","!=","==" in c notation, "gt", "lt", "eq", "ne" in shell
sh notation and "greater", "less", "equal", "notequal" in human readable form (if not
specified, default is EQUAL).
number limit.
action is a choice of "ALERT", "RESTART", "START", "STOP", "EXEC" or "UNMONITOR".
Examples:
check system $HOST
if filedescriptors >= 90% then alert
check process myproc with pidfile /var/run/myproc.pid
if filedescriptors >= 90% then alert
if filedescriptors >= 99% then restart
if total filedescriptors > 5000 then alert
PROGRAM STATUS TEST
You can check the exit status of a program or a script. This test may only be used within
a check program service entry in the Monit control file.
Syntax for testing specific exit value:
IF STATUS operator value THEN action
Syntax for testing any exit value change:
IF CHANGED STATUS THEN action
operator is a choice of "<",">","!=","==" in c notation, "gt", "lt", "eq", "ne" in shell
sh notation and "greater", "less", "equal", "notequal" in human readable form (if not
specified, default is EQUAL).
action is a choice of "ALERT", "RESTART", "START", "STOP", "EXEC" or "UNMONITOR".
Example:
check program myscript with path /usr/local/bin/myscript.sh
if status != 0 then alert
Sample script for the above example (/usr/local/bin/myscript.sh):
#!/bin/sh
echo test
exit $?
You can also send parameters with the program:
check program list-files with path "/bin/ls -lrt /tmp/"
if status != 0 then alert
Arguments to the program or script is a sequence of whitespace separated strings. In the
above example the strings '-lrt' and '/tmp/' are arguments to the program '/bin/ls'. If
arguments are used, it is recommended to use quotes " to enclose the string, otherwise, if
no arguments are used, quotes are not needed.
Notes: If the program is a script, the interpreter is required in the first line. The
program or script must also be executable.
If Monit is run as the super user, you can optionally run the program as a different user
and/or group. In this example we run the ls program as user www and as group staff:
check program ls with path "/bin/ls /tmp"
as uid "www"
and gid "staff"
if status != 0 then alert
Monit will execute the program periodically and if the exit status of the program does not
match the expected result, Monit can perform an action. In the example above, Monit will
raise an alert if the exit value is different from 0. By convention, 0 means the program
exited normally.
Program checks are asynchronous. Meaning that Monit will not wait for the program to exit,
but instead, Monit will start the program in the background and immediately continue
checking the next service entry in monitrc. At the next cycle, Monit will check if the
program has finished and if so, collect the program's exit status. If the status indicate
a failure, Monit will raise an alert message containing the program's error (stderr)
output, if any. If the program has not exited after the first cycle, Monit will wait
another cycle and so on. If the program is still running after 5 minutes, Monit will kill
it and generate a program timeout event. It is possible to override the default timeout
(see the syntax below).
Multiple status tests can be used, for example:
check program hwtest with path /usr/local/bin/hwtest.sh
with timeout 500 seconds
if status = 1 then alert
if status = 3 for 5 cycles then exec "/usr/local/bin/emergency.sh"
PROGRAM OUTPUT CONTENT TEST
The content statement can be used to either test the content of a program by using regular
expressions or check for changes in the output.
Syntax:
IF CONTENT <operator> <regex> THEN action
IF CONTENT [NOT] CHANGED THEN action
operator is either a "=" for match or "!=" for no-match.
regex is a string containing the extended regular expression. See also regex(7).
action is a choice of "ALERT", "RESTART", "START", "STOP", "EXEC" or "UNMONITOR".
By default the output check is limited to 511 characters only. You can increase the limit
using the set limits statement.
Examples:
check program disk0_smart with path "/usr/sbin/nvme smart-log /dev/nvme0"
if content != "critical_warning[ ]+: 0" then alert
check program ip_route with path "/usr/bin/ip route"
if content changed then alert
NETWORK INTERFACE TESTS
Monit can check network interfaces for:
Status
Capacity
Saturation
Upload and download [bytes]
Upload and download [packets]
Link status
You can check the network link state. This test may only be used within a check network
service entry in the Monit control file.
Syntax:
IF LINK <DOWN|UP> THEN action
action is a choice of "ALERT", "RESTART", "START", "STOP", "EXEC" or "UNMONITOR".
The DOWN test will fail if the link/interface is down or link errors were detected.
Mixing "link up" and "link down" in the same "check network" is not supported.
Examples:
check network eth0 with interface eth0
if link down then alert
check network eth5 with interface eth5
if link up then exec "/usr/bin/monit start backup"
In case a link failed you can add a start and stop program to automatically restart the
interface which might help. (Substitute with the relevant network commands for your
system)
check network eth0 with interface eth0
start program = '/sbin/ipup eth0'
stop program = '/sbin/ipdown eth0'
if link down then restart
Link capacity
You can check the network link mode capacity for changes. This test may only be used
within a check network service entry in the Monit control file.
Syntax:
IF CHANGED LINK [CAPACITY] THEN action
action is a choice of "ALERT", "RESTART", "START", "STOP", "EXEC" or "UNMONITOR".
The test will match if the link mode has changed (e.g. maximum speed dropped) or if the
duplex mode has changed.
NOTE: not all interface types allow for capacity monitoring. Pseudo interfaces such as
loopback device or VMWare interfaces does not have a speed attribute.
Example:
check network eth0 with interface eth0
if changed link capacity then alert
Link saturation
You can check the network link saturation. Monit then computes the link utilisation based
on the current transfer rate vs. link capacity. This test may only be used within a check
network service entry in the Monit control file.
Syntax:
IF SATURATION operator value% THEN action
operator is a choice of "<",">","!=","==" in c notation, "gt", "lt", "eq", "ne" in shell
sh notation and "greater", "less", "equal", "notequal" in human readable form (if not
specified, default is EQUAL).
action is a choice of "ALERT", "RESTART", "START", "STOP", "EXEC" or "UNMONITOR".
NOTE: this test depends on the availability of the speed attribute and not all interface
types have this attribute. See the LINK SPEED test description.
Example:
check network eth0 with interface eth0
if saturation > 90% then alert
Link upload and download [bytes]
You can check a network link upload and download bandwidth usage, current transfer speed
and total data transferred in the last 24 hours. This test may only be used within a check
network service entry in the Monit control file.
Upload speed test syntax (per second):
IF UPLOAD operator value unit/S THEN action
Download speed test syntax (per second):
IF DOWNLOAD operator value unit/S THEN action
Total upload data test syntax:
IF TOTAL UPLOADED operator value unit IN LAST number time-unit THEN action
Total download data test syntax:
IF TOTAL DOWNLOADED operator value unit IN LAST number time-unit THEN action
operator is a choice of "<",">","!=","==" in c notation, "gt", "lt", "eq", "ne" in shell
sh notation and "greater", "less", "equal", "notequal" in human readable form (if not
specified, default is EQUAL).
unit is a choice of "B","KB","MB","GB" or long alternatives "byte", "kilobyte",
"megabyte", "gigabyte".
time-unit is a choice of "MINUTE(S)", "HOUR(S)", "DAY". NOTE: Monit maintains a rolling
count of total uploaded and downloaded bytes for the last 24 hours only. The value of
time-unit can therefore not specify a range wider than one day.
action is a choice of "ALERT", "RESTART", "START", "STOP", "EXEC" or "UNMONITOR".
Examples:
check network eth0 with interface eth0
if upload > 500 kB/s then alert
if total downloaded > 1 GB in last 2 hours then alert
if total downloaded > 10 GB in last day then alert
Link upload and download [packets]
You can check the network link upload and download packets count, current transfer rate
and total data transferred in last 24 hours. This test may only be used within a check
network service entry in the Monit control file.
Current upload bandwidth rate test syntax:
IF UPLOAD operator value PACKETS/S THEN action
Current download bandwidth rate test syntax:
IF DOWNLOAD operator value PACKETS/S THEN action
Total upload test syntax:
IF TOTAL UPLOADED operator value PACKETS IN LAST number time-unit THEN action
Total download test syntax:
IF TOTAL DOWNLOADED operator value PACKETS IN LAST number time-unit THEN action
operator is a choice of "<",">","!=","==" in c notation, "gt", "lt", "eq", "ne" in shell
sh notation and "greater", "less", "equal", "notequal" in human readable form (if not
specified, default is EQUAL).
time-unit is a choice of "MINUTE(S)", "HOUR(S)", "DAY". NOTE: Monit keeps total
upload/download statistics only for the last 24 hours. The time-unit value cannot
therefore span more than one day.
action is a choice of "ALERT", "RESTART", "START", "STOP", "EXEC" or "UNMONITOR".
Examples:
check network eth0 with interface eth0
if upload > 1000 packets/s then alert
if total uploaded > 900000 packets in last hour then alert
NETWORK PING TEST
Monit can perform a network ping test by sending ICMP echo request datagram packets to a
host and wait for the reply. This test can only be used within a check host statement.
Monit must also run as the root user in order to be able to perform the ping test (because
the ping test must use raw sockets which usually only the super user is allowed to).
Syntax:
IF <FAILED|SUCCEEDED> PING[4|6]
[COUNT number]
[SIZE number]
[RESPONSETIME operator number <MILLISECONDS|SECONDS>]
[TIMEOUT number SECONDS]
[ADDRESS string]
THEN action
If a DNS host name was used in the check host statement and the host name resolve to
several addresses (either IPv4 or IPv6), Monit will ping the first available address and
continue with the next address until one connection succeed or until there are no more
addresses left to try. You can force Monit to only ping IPv4 or IPv6 addresses by using
the PING4 or the PING6 keyword instead of PING.
The COUNT parameter specifies how many consecutive ping requests will be sent to the host
in one cycle at maximum. The default value is 3.
The SIZE parameter specifies the ping request payload size. Default is 64 bytes, minimum
is 8 bytes, maximum 1492 bytes.
The RESPONSETIME parameter sets the response time limit. operator is a choice of
"<",">","!=","==" in c notation, "gt", "lt", "eq", "ne" in shell sh notation and
"greater", "less", "equal", "notequal" in human readable form (if not specified, default
is EQUAL).
If no reply arrive within TIMEOUT seconds, Monit reports an error. If at least one reply
was received, the ping test is considered a success.
The ADDRESS parameter specifies source IP address.
Monit will, by default, send up to three ping request packets in one cycle to prevent
false alarm (i.e. up to 66% packet loss is tolerated). You can set the COUNT option to a
value between 1 and 20 to send more or fewer packets. If you require 100% ping success,
set the count to 1 (i.e. just one request will be sent, and if the packet was lost an
error will be reported).
Note that many ISPs have started to filter out ping or ICMP packets now, in which case
there will be no reply from the host.
If a ping test is used in a check host entry, this test is run first and if the test
should fail, we assume that the connection to the host is down and Monit will not continue
with any subsequent port tests.
Example:
check host mmonit.com with address mmonit.com
if failed ping then alert # IPv4 or IPv6
check host mmonit.com with address 62.109.39.247
if failed ping then alert # Address is IPv4 so IPv4 is preferred
or test that the system is explicit accessible via IPv4 and IPv6:
check host mmonit.com with address mmonit.com
if failed ping4 then alert # IPv4 only
if failed ping6 then alert # IPv6 only
or with all parameters; Send five 128 byte pings to mmonit.com and wait for up to 10
seconds for a reply
check host mmonit.com with address mmonit.com
if failed ping count 5 size 128 with timeout 10 seconds then alert
You can also watch host, that is supposed to be offline:
check host offlinehost with address 192.168.100.50
if succeeded ping then alert
CONNECTION TESTS
Monit can perform connection testing via network ports or via Unix sockets. A connection
test may only be used within a process or host service type context.
If a service listens on one or more sockets, Monit can connect to the port (using TCP or
UDP) and verify that the service will accept a connection and that it is possible to write
and read from the socket. If a connection is not accepted or if there is a problem with
socket I/O, Monit will execute a specified action.
For TCP/UDP ports monit can alert on successful connection, e.g. when a service like mysql
should not be publicly available.
TCP/UDP port test syntax:
IF <FAILED|SUCCEEDED>
[HOST string]
<PORT number>
[ADDRESS string]
[IPV4 | IPV6]
[TYPE <TCP|UDP>]
[<SSL|TLS> [with options {...}]
[CERTIFICATE CHECKSUM [MD5|SHA1] string]
[CERTIFICATE VALID for number DAYS]
[PROTOCOL protocol | <SEND|EXPECT> "string",...]
[RESPONSETIME operator number <MILLISECONDS|SECONDS>]
[TIMEOUT number SECONDS]
[RETRY number]
THEN action
Unix socket test syntax:
IF <FAILED|SUCCEEDED>
<UNIXSOCKET path>
[TYPE <TCP|UDP>]
[PROTOCOL protocol | <SEND|EXPECT> "string",...]
[RESPONSETIME operator number <MILLISECONDS|SECONDS>]
[TIMEOUT number SECONDS]
[RETRY number]
THEN action
Examples:
if failed port 80 then alert
if failed port 53 type udp protocol dns then alert
if succeeded host example.org port 3306 type tcp protocol mysql then alert
if failed unixsocket /var/run/sophie then alert
Options:
HOST hostname. Optionally specify the host to connect to. If the host is not given then
localhost is assumed if this test is used inside a process entry. If this test is used
inside a remote host entry then the entry's remote host is assumed.
PORT number. The port number to connect to
UNIXSOCKET path. Specifies the path to a Unix socket (local machine only).
ADDRESS string. The source IP address to use.
IPV4 | IPV6 . Optionally specify the IP version Monit should use when trying to connect to
the port. If not used, Monit will try to connect to the first available address (IPv4 or
IPv6). If multiple addresses are available and connection to one address failed, Monit
will try the next address and so on until a connection succeed or until there are no more
addresses left to try.
TYPE [TCP | UDP]. Optionally specify the socket type Monit should use when trying to
connect to the port. The different socket types are: TCP or UDP, where TCP is a regular
stream based socket, UDP, a datagram socket. The default socket type is TCP.
[SSL | TLS] [with options {...}]. Set SSL/TLS options and override global/default SSL
options. You can set the SSL/TLS version to use, whether to verify certificates, trust
self-signed certificates or set the SSL client certificates database-file for client
certificate authentication.
CERTIFICATE CHECKSUM [MD5|SHA1] hash. Verify the SSL server certificate by checking its
checksum. You can use either MD5 or SHA1 checksum (if you don't specify the type, Monit
will determine the digest based on the hash length). You can use the openssl command line
tool to get the checksum value for your certificate, which you can then use in Monit's
control file:
openssl x509 -fingerprint -sha1 -in server.crt | head -1 | cut -f2 -d'='
Example:
if failed
port 443
protocol https
and certificate checksum = "1ED948A6F4258ACAB964227EF4EB19FCC453B0F8"
then alert
CERTIFICATE VALID for number DAYS. Send an alert if the certificate will expire in the
given number of days. This test is pretty useful to get a notification when it is time to
renew your SSL certificate.
Example:
if failed
port 443
protocol https
and certificate valid > 30 days
then alert
PROTOCOL protocol. Optionally specify the protocol Monit should speak when a connection is
established. At the moment Monit knows how to speak:
APACHE-STATUS
DNS
DWP
FAIL2BAN
FTP
GPS
HTTP
HTTPS
IMAP
IMAPS
CLAMAV
LDAP2
LDAP3
LMTP
MEMCACHE
MONGODB
MQTT
MYSQL
MYSQLS
NNTP
NTP3
PGSQL
POP
POPS
POSTFIX-POLICY
RADIUS
RDATE
REDIS
RSYNC
SIEVE
SIP
SMTP
SMTPS
SPAMASSASSIN
SSH
TNS
WEBSOCKET
If the target server's protocol is not found in this list, simply do not specify the
protocol and Monit will use a default connection test.
RESPONSETIME parameter sets the response time limit. operator is a choice of
"<",">","!=","==" in c notation, "gt", "lt", "eq", "ne" in shell sh notation and
"greater", "less", "equal", "notequal" in human readable form (if not specified, default
is EQUAL).
TIMEOUT number SECONDS. Optionally specifies the connect and read timeout for the
connection. If Monit cannot connect to the server within this time it will assume that the
connection failed and execute the specified action. The default connect timeout is 5
seconds.
RETRY number. Optionally specifies the number of consecutive retries within the same
testing cycle in the case that the connection failed. The default is fail on first error.
action is a choice of "ALERT", "RESTART", "START", "STOP", "EXEC" or "UNMONITOR".
Specific protocol test options
GENERIC (SEND/EXPECT)
If Monit does not support the protocol spoken by the server, you can write your own
protocol-test using send and expect strings. The SEND statement sends a string to the
server port and the EXPECT statement compares a string read from the server with the
string given in the expect statement.
Syntax:
[<SEND|EXPECT> "string"]+
Monit will send a string as it is, and you must remember to include CR and LF in the
string sent to the server if the protocol expects such characters to terminate a string
(most text based protocols used over Internet do).
Monit will by default read up to 255 bytes from the server and use this string when
comparing the EXPECT string. You can override the default value using the set limits
statement.
You can use non-printable characters in a SEND string if needed. Use the hex notation,
\0xHEXHEX to send any char in the range \0x00-\0xFF, that is, 0-255 in decimal. For
example, to test a Quake 3 server:
send "\0xFF\0xFF\0xFF\0xFFgetstatus"
expect "sv_floodProtect|sv_maxPing"
If your system supports POSIX regular expressions, you can use regular expressions in the
EXPECT string, see regex(7) to learn more about the types of regular expressions you can
use in an expect string.
Since both regex and string compare operates on a zero terminated string, you cannot test
for '\0' in an EXPECT buffer since this character marks the end of the buffer. However, we
escape '\0' in the expect buffer as "\0" which you can test for. That is, '\' followed by
the ascii value for 0. For instance, here is how to test for an expect string that starts
with zero followed by any number of characters.
expect "^[\\]0.*"
Here is a simple SMTP protocol example:
if failed
port 25 and
expect "^220.*"
send "HELO localhost.localdomain\r\n"
expect "^250.*"
send "QUIT\r\n"
then alert
SEND/EXPECT can be used with any socket type, such as TCP sockets, UNIX sockets and UDP
sockets.
HTTP
Syntax:
PROTO(COL) HTTP
[USERNAME "string"]
[PASSWORD "string"]
[REQUEST "string"]
[METHOD <GET|HEAD>]
[STATUS operator number]
[CHECKSUM checksum]
[HTTP HEADERS list of headers]
[CONTENT < "=" | "!=" > STRING]
USERNAME is an optional username for Basic authentication
PASSWORD is an optional password for Basic authentication
REQUEST option can set an URL string specifying a document on the HTTP server. If the
request statement isn't specified, the default "/" page will be requested.
For example:
if failed
port 80
protocol http
request "/data/show?a=b&c=d"
then restart
METHOD set the HTTP request method. If not specified, Monit prefers the HTTP GET request
method, which is more common then the HEAD method. One may want to set the method
explicitly to HEAD to save the network bandwidth.
STATUS option can be used to explicitly test the HTTP status code returned by the HTTP
server. If not used, the HTTP protocol test will fail if the status code returned is
greater than or equal to 400. You can override this behaviour by using the status
qualifier.
For example to test that a page does not exist (the HTTP server should return 404 in this
case):
if failed
port 80
protocol http
request "/non/existent.php"
status = 404
then alert
CHECKSUM You can test the checksum of documents returned by a HTTP server. Either MD5 or
SHA1 hash can be used. Monit will not test the checksum for a document if the server does
not set the HTTP Content-Length header. A HTTP server should set this header when it
server a static document (i.e. a file). There are no limitation on the document size, but
keep in mind that Monit will use time to download the document over the network to compute
the checksum.
Example:
if failed
port 80
protocol http
request "/page.html"
checksum 8f7f419955cefa0b33a2ba316cba3659
then alert
HTTP HEADERS can be used to send a list of HTTP headers when using the HTTP protocol test.
For instance, the host header. If the host header is not set, Monit will use the hostname
or IP-address of the host as specified in the check host statement. Specifying a host
header is useful if you want to connect to and test a name-based virtual host. The syntax
for setting HTTP headers is
http headers [name:value, name:value,..]
where each name:value pair is separated with ','. If you need to use ':' in the value
string, for instance to set port number for a host header, you must enclose the value in
quotes. For example,
http headers [Host: "mmonit.com:443"]
In a check host context, using this statement might look like
check host mmonit.com with address mmonit.com
if failed
port 80 protocol http
with http headers [Host: mmonit.com, Cache-Control: no-cache,
Cookie: csrftoken=nj1bI3CnMCaiNv4beqo8ZaCfAQQvpgLH]
and request /monit/ with content = "Monit [0-9.]+"
then alert
Setting HTTP headers is associated with the HTTP protocol test and must come before
request as in the example above.
The CONTENT option sets the pattern which is expected in the data returned by the server.
If the pattern doesn't match, the test fails. In the example above, if the server does not
return a page with the name Monit followed by a version number the test will fail.
By default, at maximum 1MB of content is inspected. You can increase this limit using the
set limits statement.
For example:
if failed
port 80
protocol http
content = "foobar [0-9.]+"
then alert
APACHE-STATUS
The APACHE-STATUS test allows one to check server performance by examination of the status
page generated by Apache's mod_status, which is expected to be at its default address of
http://www.example.com/server-status.
Syntax:
PROTOCOL APACHE-STATUS [PATH <path>] [USERNAME <string>] [PASSWORD <string>] [<property> <operator> <number>]+
PATH is an optional path to apache status ("/server-status" by default)
USERNAME is an optional username for Basic authentication
PASSWORD is an optional password for Basic authentication
property is acronym for child status:
(1) logging (loglimit)
(2) closing connections (closelimit)
(3) performing DNS lookups (dnslimit)
(4) in keepalive with a client (keepalivelimit)
(5) replying to a client (replylimit)
(6) receiving a request (requestlimit)
(7) initialising (startlimit)
(8) waiting for incoming connections (waitlimit)
(9) gracefully closing down (gracefullimit)
(10) performing cleanup procedures (cleanuplimit)
operator is one of "<", "=", ">".
number is percentile numeric limit.
Each of these limits can be compared against a value relative to the total number of
active Apache child processes.
You can combine all of these tests into one expression or you can choose to test a certain
limit only. If you combine the limits you must connect them together using the OR keyword.
Example:
if failed port 80 protocol apache-status
loglimit > 10% or
dnslimit > 50% or
waitlimit < 20%
then alert
MQTT
Syntax:
PROTOCOL MQTT [USERNAME string PASSWORD string]
USERNAME MQTT username
PASSWORD MQTT password
Username and password (credentials) are optional. If not used, Monit will try anonymous
connect, which may trigger authorization error => credentials are recommended unless your
server allows anonymous connect.
Example:
check process mosquitto with pidfile /var/run/mosquitto.pid
start program = "/sbin/start mosquitto"
stop program = "/sbin/stop mosquitto"
if failed port 1883 protocol mqtt then alert
MYSQL
Syntax:
PROTOCOL MYSQL[S] [USERNAME string PASSWORD string [RSAKEY CHECKSUM string]]
USERNAME MySQL username.
PASSWORD MySQL password (special characters can be used, but for non-alphanumerics the
password has to be quoted).
RSKEY CHECKSUM If you use unsecured connection (plain MYSQL without TLS), you can set the
expected MD5 or SHA1 checksum of the server's RSA key to protect afainst man-in-the-middle
attacks. Monit will check the key fingerprint before sending the password to the server.
Username and password (credentials) are optional and if not set, Monit will perform the
test using anonymous login. This can cause an authentication error to be logged in your
MySQL log, depending on your MySQL configuration.
If credentials are set, Monit will try to login. Monit does not require any database
privileges, it just needs the database user. You might want to create standalone user for
Monit to use when testing, for example:
CREATE USER 'monit'@'host_from_which_monit_performs_testing' IDENTIFIED BY 'mysecretpassword';
FLUSH PRIVILEGES;
Example:
check process mysql with pidfile /var/run/mysqld/mysqld.pid
start program = "/sbin/start mysql"
stop program = "/sbin/stop mysql"
if failed
port 3306
protocol mysql username "foo" password "bar"
then alert
or with unix-socket start/stop commands
check process mysql with pidfile /var/run/mysqld/mysqld.pid
start program = "/usr/local/mysql/support-files/mysql.server start"
stop program = "/usr/local/mysql/support-files/mysql.server stop"
if failed
unixsocket /tmp/mysql.sock
protocol mysql username "foo" password "bar"
then alert
You can enable the TLS encryption for the test by using MYSQLS as protocol name:
if failed
port 3306
protocol mysqls username "foo" password "bar"
then alert
PGSQL
Syntax:
PROTOCOL PGSQL [USERNAME string] [PASSWORD string] [DATABASE string]]
USERNAME PostgreSQL username.
PASSWORD PostgreSQL password (special characters can be used, but for non-alphanumerics
the password has to be quoted).
DATABASE PostgreSQL database (defaults to the database that matches the username if not
set).
Username and password (credentials) are optional and if not set, Monit will perform the
test with hardcoded user=root and database=root, which may trigger errors in PostgreSQL
logs.
If credentials are set, Monit will try to login. You might want to create standalone user
for Monit to use when testing.
Monit currently supports only 'password' and 'md5' PostgreSQL authentication methods. If
the server asks for authentication method that Monit doesn't support (such as
'scram-sha-256'), Monit terminates the connection and the test succeeds (although monit
cannot authenticate, the server is communicating).
To allow access to Monit for testing purposes, one can create an account and allow access
for example like this:
PostgreSQL pg_hba.conf entry example:
# TYPE DATABASE USER ADDRESS METHOD
host test monit 127.0.0.1/32 md5
Monit configurations example:
check process postgresql with pidfile /var/run/postgresql/12-main.pid
start program = "/bin/systemctl postgresql start"
stop program = "/bin/systemctl postgresql stop"
if failed
port 5432
protocol pgsql username "monit" password "123456" database "test"
then alert
RADIUS
Syntax:
PROTOCOL RADIUS [SECRET string]
SECRET you may specify an alternative secret, default is "testing123".
For example:
check process radiusd with pidfile /var/run/radiusd.pid
start program = "/etc/init.d/freeradius start"
stop program = "/etc/init.d/freeradius stop"
if failed
host 127.0.0.1 port 1812 type udp protocol radius
secret pingpong
then alert
SIP
The SIP protocol is used by communication platform servers such as Asterisk and
FreeSWITCH.
Syntax:
PROTOCOL SIP [TARGET valid@uri] [MAXFORWARD n]
TARGET you may specify an alternative recipient for the message, by adding a valid sip uri
after this keyword.
MAXFORWARD Limit the number of proxies or gateways that can forward the request to the
next server. It's value is an integer in the range 0-255, set by default to 70. If max-
forward = 0, the next server may respond 200 OK (test succeeded) or send a 483 Too Many
Hops (test failed)
For example:
check host openser_all with address 127.0.0.1
if failed
port 5060 type udp protocol sip
with target "localhost:5060" and maxforward 6
then alert
SMTP
Syntax:
PROTOCOL SMTP[S] [USERNAME string PASSWORD string]
USERNAME SMTP username.
PASSWORD SMTP password (special characters can be used, but for non-alphanumerics the
password has to be quoted).
Credentials are optional and when used will perform authentication during testing so you
can test that authentication also works. We recommend using smtps if authentication is to
be used to encrypt the communication. If no credentials are set, Monit will just perform a
basic protocol test.
Example:
check process postfix with pidfile /var/spool/postfix/pid/master.pid
start program = "/etc/init.d/postfix start"
stop program = "/etc/init.d/postfix stop"
if failed
port 25
protocol smtp
then alert
Example using authentication and STARTTLS/SMTPS:
check process postfix with pidfile /var/spool/postfix/pid/master.pid
start program = "/etc/init.d/postfix start"
stop program = "/etc/init.d/postfix stop"
if failed
port 25
protocol smtps
username "foo"
password "bar"
then alert
WEBSOCKET
Syntax:
PROTOCOL WEBSOCKET
[REQUEST string]
[HOST string]
[ORIGIN string]
[VERSION number]
HOST you may specify an alternative Host header
REQUEST you may specify an alternative request, default is "/"
ORIGIN you may specify an alternative origin, default is "https://mmonit.com"
VERSION you may specify an alternative version, default is "0"
For example:
check host websocket.org with address "echo.websocket.org"
if failed
port 80 protocol websocket
host "echo.websocket.org"
request "/"
origin 'http://websocket.com'
version 13
then alert
MANAGE YOUR MONIT INSTANCES
M/Monit <https://mmonit.com> expands on Monit's capabilities and provides monitoring and
management of all your Monit enabled hosts.
M/Monit uses Monit as an agent. With regular intervals, Monit sends a status message to
M/Monit with a snapshot of the host it is running on.
M/Monit presents the collected data in charts and event logs and give you the option to
view key performance data of all your hosts in a modern, clean and well designed user
interface which also works on mobile devices.
From M/Monit, you can also start, stop and restart services on your hosts running Monit.
To send data to M/Monit, add the following statement to your Monit control file:
SET MMONIT <url>
[TIMEOUT <number> SECONDS]
[REGISTER WITHOUT CREDENTIALS]
[[WITH] HOSTGROUPS '[' "name", ... ']' ]
Example:
set mmonit https://monit:monit@192.168.1.10:8443/collector
Monit will register itself in M/Monit and will start sending status and event messages to
M/Monit. We recommend using https as in the example above to ensure that the communication
between Monit and M/Monit is secure.
The password should be URL encoded if it contains URL-significant characters like ":",
"?", "@".
The default timeout is 5 seconds, you can customise the timeout using the TIMEOUT option.
When Monit registers itself in M/Monit it sends credentials that can be used to perform
service actions from M/Monit. You can disable sending credentials by using REGISTER
WITHOUT CREDENTIALS and instead manually add credentials in M/Monit.
You can optionally add Monit to one or more M/Monit hostgroups. If the hostgroup doesn't
exist, it'll be created automatically. Example:
set mmonit
https://monit:monit@192.168.1.10:8443/collector
with hostgroups [ Oslo, "Mail servers" ]
CONFIGURATION EXAMPLES
The simplest form is just the check statement. In this example we check to see if our web
server is running and raise an alert if not:
check process nginx with pidfile /var/run/nginx.pid
To have Monit start the server if it's not running, add a start statement:
check process nginx with pidfile /var/run/nginx.pid
start program = "/etc/init.d/nginx start"
Here's a more advanced example for monitoring an apache web-server listening on the
default port number for HTTP and HTTPS. In this example Monit will restart apache if it's
not accepting connections at the port numbers. The method Monit use for restart is to
first execute the stop-program, then wait (up to 30s) for the process to stop and then
execute the start-program and wait (30s) for it to start. The length of start or stop wait
can be overridden using the 'timeout' option. If Monit was unable to stop or start the
service a failed alert message will be sent if you have requested alert messages to be
sent.
check process apache with pidfile /var/run/httpd.pid
start program = "/etc/init.d/httpd start" with timeout 60 seconds
stop program = "/etc/init.d/httpd stop"
if failed port 80 for 2 cycles then restart
if failed port 443 for 2 cycles then restart
This example demonstrate how you can run a program as a specified user (uid) and with a
specified group (gid). Many daemon programs can do the uid and gid switch by themselves,
but for those programs that does not (e.g. Java programs), monit's ability to start a
program as a certain user can be very useful. In this example we start the Tomcat Java
Servlet Engine as the standard nobody user and group. Please note that Monit can only
switch uid and gid for the program if the super-user is running Monit, otherwise Monit
will simply ignore the request to change uid and gid.
check process tomcat with pidfile /var/run/tomcat.pid
start program = "/etc/init.d/tomcat start"
as uid "nobody" and gid "nobody"
stop program = "/etc/init.d/tomcat stop"
# You can also use id numbers instead and write:
as uid 99 and with gid 99
if failed port 8080 then alert
In this example we use udp for connection testing to check if the name-server is running:
check process named with pidfile /var/run/named.pid
start program = "/etc/init.d/named start"
stop program = "/etc/init.d/named stop"
if failed port 53 use type udp protocol dns then restart
The following example illustrates how to check if the service 'sophie' is answering
connections on its Unix domain socket:
check process sophie with pidfile /var/run/sophie.pid
start program = "/etc/init.d/sophie start"
stop program = "/etc/init.d/sophie stop"
if failed unix /var/run/sophie then restart
In this example we check an apache web-server running on localhost which answers for
several IP-based virtual hosts or vhosts, hence the host statement before port:
check process apache with pidfile /var/run/httpd.pid
start "/etc/init.d/httpd start"
stop "/etc/init.d/httpd stop"
if failed host www.sol.no port 80 then alert
if failed host shop.sol.no port 443 then alert
if failed host chat.sol.no port 80 then alert
To make sure that Monit is communicating with a HTTP server a protocol test can be added:
check process apache with pidfile /var/run/httpd.pid
start "/etc/init.d/httpd start"
stop "/etc/init.d/httpd stop"
if failed
host www.sol.no port 80 protocol http
then alert
This example demonstrate a different way to check a web-server using the send/expect
mechanism:
check process apache with pidfile /var/run/httpd.pid
start "/etc/init.d/httpd start"
stop "/etc/init.d/httpd stop"
if failed
host www.sol.no port 80 and
send "GET / HTTP/1.1\r\nHost: www.sol.no\r\n\r\n"
expect "HTTP/[0-9\.]{3} 200.*"
then alert
Here we ping a remote host to check if it is up and if not, send an alert:
check host www.tildeslash.com with address www.tildeslash.com
if failed ping then alert
In the following example we ask Monit to compute and verify the checksum for the
underlying apache binary used by the start and stop programs. If the checksum test should
fail, monitoring will be disabled to prevent possibly restarting a compromised binary:
check process apache with pidfile /var/run/httpd.pid
start program = "/etc/init.d/httpd start"
stop program = "/etc/init.d/httpd stop"
if failed host www.tildeslash.com port 80 then restart
depends on apache_bin
check file apache_bin with path /usr/local/apache/bin/httpd
if failed checksum then unmonitor
In this example we ask Monit to test a document's checksum on a remote server. If the
checksum was changed we send an alert:
check host mmonit.com with address mmonit.com
if failed
port 80 protocol http and
request "/monit/dist/monit-5.7.tar.gz"
with checksum f9d26b8393736b5dfad837bb13780786
then alert
Here are a couple of tests for some popular communication servers, using the SIP protocol.
First we test a FreeSWITCH server and then an Asterisk server
check process freeswitch
with pidfile /usr/local/freeswitch/log/freeswitch.pid
start program = "/usr/local/freeswitch/bin/freeswitch -nc -hp"
stop program = "/usr/local/freeswitch/bin/freeswitch -stop"
if total memory > 1000.0 MB for 5 cycles then alert
if total memory > 1500.0 MB for 5 cycles then alert
if total memory > 2000.0 MB for 5 cycles then restart
if cpu > 60% for 5 cycles then alert
if failed
port 5060 type udp protocol SIP
target me@foo.bar and maxforward 10
then restart
check process asterisk
with pidfile /var/run/asterisk/asterisk.pid
start program = "/usr/sbin/asterisk"
stop program = "/usr/sbin/asterisk -r -x 'shutdown now'"
if total memory > 1000.0 MB for 5 cycles then alert
if total memory > 1500.0 MB for 5 cycles then alert
if total memory > 2000.0 MB for 5 cycles then restart
if cpu > 60% for 5 cycles then alert
if failed
port 5060 type udp protocol SIP
and target me@foo.bar maxforward 10
then restart
Some servers are slow starters, like for example Java based Application Servers. If we
want to keep the poll-cycle low (i.e. < 60 seconds) but allow some services to take its
time to start, the every statement is handy:
check process dynamo with pidfile /etc/dynamo.pid every 2 cycles
start program = "/etc/init.d/dynamo start"
stop program = "/etc/init.d/dynamo stop"
if failed port 8840 then alert
Here is an example where we group together two database entries so you can manage them
together, e.g.; 'Monit -g database start all'. The mode statement is also illustrated in
the first entry and have the effect that Monit will not try to (re)start this service if
it is not running:
check process sybase with pidfile /var/run/sybase.pid
start = "/etc/init.d/sybase start"
stop = "/etc/init.d/sybase stop"
mode passive
group database
check process oracle with pidfile /var/run/oracle.pid
start program = "/etc/init.d/oracle start"
stop program = "/etc/init.d/oracle stop"
if failed
port 9001 protocol tns
then restart
group database
This resource checks example will send an alert if CPU usage of the Apache's HTTP daemon
and its child processes goes beyond 60% for two cycles. Apache is restarted if the CPU
usage is over 80% for five cycles or the memory usage is over 100Mb for five cycles:
check process apache with pidfile /var/run/httpd.pid
start program = "/etc/init.d/httpd start"
stop program = "/etc/init.d/httpd stop"
if cpu > 40% for 2 cycles then alert
if total cpu > 60% for 2 cycles then alert
if total cpu > 80% for 5 cycles then restart
if mem > 100 MB for 5 cycles then stop
This examples demonstrate the timestamp statement with exec and how you may restart apache
if its configuration file was changed.
check file httpd.conf with path /etc/httpd/httpd.conf
if changed timestamp
then exec "/etc/init.d/httpd graceful"
In this example we demonstrate usage of the extended alert statement and a file check
dependency:
check process apache with pidfile /var/run/httpd.pid
start = "/etc/init.d/httpd start"
stop = "/etc/init.d/httpd stop"
alert admin@bar on {nonexist, timeout}
with mail-format {
from: bofh@$HOST
subject: apache $EVENT - $ACTION
message: This event occurred on $HOST at $DATE.
Your faithful employee,
monit
}
if failed host www.tildeslash.com port 80 then restart
depend httpd_bin
group apache
check file httpd_bin with path /usr/local/apache/bin/httpd
alert security@bar on {checksum, timestamp,
permission, uid, gid}
with mail-format {subject: Alaaarrm! on $HOST}
if failed checksum
and expect 8f7f419955cefa0b33a2ba316cba3659
then unmonitor
if failed permission 755 then unmonitor
if failed uid "root" then unmonitor
if failed gid "root" then unmonitor
if changed timestamp then alert
group apache
In this example, we demonstrate usage of the depend statement. In this case, we want to
start oracle and apache. However, we've set up apache to use oracle as a back end, and if
oracle is restarted, apache must be restarted as well.
check process apache with pidfile /var/run/httpd.pid
start = "/etc/init.d/httpd start"
stop = "/etc/init.d/httpd stop"
depends on oracle
check process oracle with pidfile /var/run/oracle.pid
start = "/etc/init.d/oracle start"
stop = "/etc/init.d/oracle stop"
if failed port 9001 for 5 cycles then restart
Next, we have 2 services, oracle-import and oracle-export that need to be restarted if
oracle is restarted, but are independent of each other.
check process oracle with pidfile /var/run/oracle.pid
start = "/etc/init.d/oracle start"
stop = "/etc/init.d/oracle stop"
if failed port 9001 for 3 cycles then restart
check process oracle-import
with pidfile /var/run/oracle-import.pid
start = "/etc/init.d/oracle-import start"
stop = "/etc/init.d/oracle-import stop"
depends on oracle
check process oracle-export
with pidfile /var/run/oracle-export.pid
start = "/etc/init.d/oracle-export start"
stop = "/etc/init.d/oracle-export stop"
depends on oracle
FILES
~/.monitrc
Default run control file
/etc/monitrc
If the control file is not found in the default
location and /etc contains a monitrc file, this
file will be used instead.
./monitrc
If the control file is not found in either of the
previous two locations, and the current working
directory contains a monitrc file, this file is
used instead.
~/.monit.pid
Lock file to help prevent concurrent runs (non-root
mode).
/run/monit.pid
Lock file to help prevent concurrent runs (root mode,
Linux systems, if /run directory is available).
/var/run/monit.pid
Lock file to help prevent concurrent runs (root mode,
Linux systems).
/etc/monit.pid
Lock file to help prevent concurrent runs (root mode,
systems without /var/run).
~/.monit.state
Monit saves its state to this file and utilises
information found in this file to recover from
a crash. This is a binary file and its content is
only of interest to monit. You may set the location
of this file in the Monit control file or by using
the -s switch when Monit is started.
~/.monit.id
Monit save its unique id to this file.
ENVIRONMENT
No environment variables are used by Monit. However, when Monit executes a
start/stop/restart program or an exec action, it will set several environment variables
which can be utilised by the executable to get information about the event, which
triggered the action.
The following environment variable is set for every program executed by monit, including
check program:
MONIT_SERVICE
The name of the service (from monitrc) for which the program is executed.
The following environment variables are only available in the service start/stop/restart
program and exec action context:
MONIT_EVENT
The event that occurred on the service
MONIT_DESCRIPTION
A description of the error condition
MONIT_DATE
The time and date (RFC 822 style) the event occurred
MONIT_HOST
The host the event occurred on
The following environment variables are only available in the check process
start/stop/restart program and exec action context:
MONIT_PROCESS_PID
The process pid. This may be 0 if the process was (re)started,
MONIT_PROCESS_MEMORY
Process memory. This may be 0 if the process was (re)started,
MONIT_PROCESS_CHILDREN
Process children. This may be 0 if the process was (re)started,
MONIT_PROCESS_CPU_PERCENT
Process cpu%. This may be 0 if the process was (re)started,
The following environment variables are only available for check program
start/stop/restart program and exec action context:
MONIT_PROGRAM_STATUS
The program status (exit value).
The following environment variables can be used for debugging:
SSLKEYLOGFILE
To debug the SSL/TLS connections, Monit supports the SSLKEYLOGFILE=<path> environment
variable in debug mode (with the -v option). The log file can be used with Wireshark
to decrypt the SSL/TLS communication (set the path to the logfile in Wireshark's
"Settings -> Protocols -> TLS -> (Pre)-Master-Secret log filename".
SIGNALS
If a Monit daemon is running, SIGUSR1 wakes it up from its sleep phase and forces a poll
of all services. SIGTERM and SIGINT will gracefully terminate a Monit daemon. The SIGTERM
signal is sent to a Monit daemon if Monit is started with the quit action argument.
Sending a SIGHUP signal to a running Monit daemon will force the daemon to reinitialise
itself, specifically it will reread configuration, close and reopen log files.
Running Monit in foreground while a background Monit daemon is running will wake up the
daemon.
NOTES
This is a very silent program. Use the -v switch if you want to see what Monit is doing,
and tail -f the log file. Optionally for testing purposes; you can start Monit with the
-Iv switch. Monit will then print debug information to the console, to stop monit in this
mode, simply press CTRL^C (i.e. SIGINT) in the same console.
The syntax (and parser) of the control file was inspired by Eric S. Raymond et al.'s
excellent fetchmail program. Some portions of this man page also receive inspiration from
the same authors.
COPYRIGHT
Copyright (C) 2001-2024 by Tildeslash Ltd. All Rights Reserved. This product is
distributed in the hope that it will be useful, but WITHOUT any warranty; without even the
implied warranty of MERCHANTABILITY or FITNESS for a particular purpose.
SEE ALSO
GNU text utilities; md5sum(1); sha1sum(1); openssl(1); glob(7); regex(7);
https://mmonit.com