Provided by: pcp_6.2.0-1.1build4_amd64 
NAME
pmcd - performance metrics collector daemon
SYNOPSIS
pmcd [-AfQSv?] [-c config] [-H hostname] [-i ipaddress] [-l logfile] [-L bytes] [-[n|N] pmnsfile] [-p
port[,port ...]] [-q timeout] [-s sockname] [-t timeout] [-T traceflag] [-U username] [-x file]
DESCRIPTION
pmcd is the collector used by the Performance Co-Pilot (see PCPIntro(1)) to gather performance metrics on
a system. As a rule, there must be an instance of pmcd running on a system for any performance metrics
to be available to the PCP.
pmcd accepts connections from client applications running either on the same machine or remotely and
provides them with metrics and other related information from the machine that pmcd is executing on.
pmcd delegates most of this request servicing to a collection of Performance Metrics Domain Agents (or
just agents), where each agent is responsible for a particular group of metrics, known as the domain of
the agent. For instance, the postgresql agent is responsible for reporting information relating to the
PostgreSQL database, such as the transaction and query counts, indexing and replication statistics, and
so on.
The agents may be processes started by pmcd, independent processes or Dynamic Shared Objects (DSOs, see
dlopen(3)) attached to pmcd's address space. The configuration section below describes how connections
to agents are specified.
Note that if a PDU exchange with an agent times out, the agent has violated the requirement that it
delivers metrics with little or no delay. This is deemed a protocol failure and the agent is
disconnected from pmcd. Any subsequent requests for information from the agent will fail with a status
indicating that there is no agent to provide it.
It is possible to specify access control to pmcd based on users, groups and hosts. This allows one to
prevent users, groups of users, and certain hosts from accessing the metrics provided by pmcd and is
described in more detail in the access control section below.
OPTIONS
The available command line options are:
-A Disable service advertisement. By default, pmcd will advertise its presence on the network using
any available mechanisms (such as Avahi/DNS-SD), assisting remote monitoring tools with finding it.
These mechanisms are disabled with this option.
-c config, --config=config
On startup pmcd uses a configuration file from either the $PCP_PMCDCONF_PATH, configuration variable
in /etc/pcp.conf, or an environment variable of the same name. However, these values may be
overridden with config using this option. The format of this configuration file is described below.
-f, --foreground
By default pmcd is started as a daemon. The -f option indicates that it should run in the
foreground. This is most useful when trying to diagnose problems with misbehaving agents.
-H hostname, --hostname=hostname
This option can be used to set the hostname that pmcd will use to represent this instance of itself.
This is used by client tools like pmlogger(1) when reporting on the (possibly remote) host. If this
option is not set, the pmcd.hostname metric will match that returned by pmhostname(1). Refer to the
manual page for that tool for full details on how the hostname is evaluated.
-i ipaddress, --interface=ipaddress
This option is usually only used on hosts with more than one network interface. If no -i options
are specified pmcd accepts connections made to any of its host's IP (Internet Protocol) addresses.
The -i option is used to specify explicitly an IP address that connections should be accepted on.
ipaddress should be in the standard dotted form (e.g. 100.23.45.6). The -i option may be used
multiple times to define a list of IP addresses. Connections made to any other IP addresses the
host has will be refused. This can be used to limit connections to one network interface if the
host is a network gateway. It is also useful if the host takes over the IP address of another host
that has failed. In such a situation only the standard IP addresses of the host should be given
(not the ones inherited from the failed host). This allows PCP applications to determine that a
host has failed, rather than connecting to the host that has assumed the identity of the failed
host.
-l logfile, --log=logfile
By default a log file named pmcd.log is written in the directory $PCP_LOG_DIR/pmcd. The -l option
causes the log file to be written to logfile instead of the default. If the log file cannot be
created or is not writable, output is written to the standard error instead.
-L bytes
PDUs received by pmcd from monitoring clients are restricted to a maximum size of 65536 bytes by
default to defend against Denial of Service attacks. The -L option may be used to change the
maximum incoming PDU size.
-n pmnsfile, --namespace=pmnsfile
Normally pmcd loads the default Performance Metrics Name Space (PMNS) from $PCP_VAR_DIR/pmns/root,
however if the -n option is specified an alternative namespace is loaded from the file pmnsfile.
-N pmnsfile, --uniqnames=pmnsfile
Same function as -n, except for the handling of duplicate Performance Metric Identifiers (PMIDs) in
pmnsfile - duplicate names are allowed with -n but they are not allowed with -N.
-p port, --port=port
Specify port to listen on. By default port 44321 is used.
-q timeout
The pmcd to agent version exchange protocol (new in PCP 2.0 - introduced to provide backward
compatibility) uses this timeout to specify how long pmcd should wait before assuming that no
version response is coming from an agent. If this timeout is reached, the agent is assumed to be an
agent which does not understand the PCP 2.0 protocol. The default timeout interval is three
seconds, but the -q option allows an alternative timeout interval (which must be greater than zero)
to be specified. The unit of timeout is seconds. Alternatively, if -q is not used, the
PMCD_CREDS_TIMEOUT environment valriable may be used to define the timeout interval.
-Q, --remotecert
Require that all remote client connections provide a certficate.
-s sockname, --socket=sockname
Specify the path to a local unix domain socket (for platforms supporting this socket family only).
The default value is $PCP_RUN_DIR/pmcd.socket.
-S, --reqauth
Require that all client connections provide user credentials. This means that only unix domain
sockets, or authenticated connections are permitted (requires secure sockets support). If any user
or group access control requirements are specified in the pmcd configuration file, then this mode of
operation is automatically entered, whether the -S flag is specified or not.
-t timeout
To prevent misbehaving clients or agents from hanging the entire Performance Metrics Collection
System (PMCS), pmcd uses timeouts on PDU exchanges with clients and agents running as processes. By
default the timeout interval is five seconds. The -t option allows an alternative timeout interval
in seconds to be specified. If timeout is zero, timeouts are turned off. It is almost impossible
to use the debugger interactively on an agent unless timeouts have been turned off for its "parent"
pmcd.
Once pmcd is running, the timeout may be dynamically modified by storing an integer value (the
timeout in seconds) into the metric pmcd.control.timeout via pmstore(1).
-T traceflag, --trace=traceflag
To assist with error diagnosis for agents and/or clients of pmcd that are not behaving correctly, an
internal event tracing mechanism is supported within pmcd. The value of traceflag is interpreted as
a bit field with the following control functions:
1 enable client connection tracing
2 enable PDU tracing
256 unbuffered event tracing
By default, event tracing is buffered using a circular buffer that is over-written as new events are
recorded. The default buffer size holds the last 20 events, although this number may be over-ridden
by using pmstore(1) to modify the metric pmcd.control.tracebufs.
Similarly once pmcd is running, the event tracing control may be dynamically modified by storing 1
(enable) or 0 (disable) into the metrics pmcd.control.traceconn, pmcd.control.tracepdu and
pmcd.control.tracenobuf. These metrics map to the bit fields associated with the traceflag argument
for the -T option.
When operating in buffered mode, the event trace buffer will be dumped whenever an agent connection
is terminated by pmcd, or when any value is stored into the metric pmcd.control.dumptrace via
pmstore(1).
In unbuffered mode, every event will be reported when it occurs.
-U username, --username=USER
User account under which to run pmcd. The default is the unprivileged "pcp" account in current
versions of PCP, but in older versions the superuser account ("root") was used by default.
-v, --verify
Verify the pmcd configuration file, reporting on any errors then exiting with a status indicating
verification success or failure.
-x file
Before the pmcd logfile can be opened, pmcd may encounter a fatal error which prevents it from
starting. By default, the output describing this error is sent to /dev/tty but it may redirected to
file.
-?, --help
Display usage message and exit.
CONFIGURATION
On startup pmcd looks for a configuration file named $PCP_PMCDCONF_PATH. This file specifies which
agents cover which performance metrics domains and how pmcd should make contact with the agents. An
optional section specifying access controls may follow the agent configuration data.
Warning: pmcd is usually started as part of the boot sequence and runs initially as root. The
configuration file may contain shell commands to create agents, which will be executed by root. To
prevent security breaches the configuration file should be writable only by root. The use of absolute
path names is also recommended.
The case of the reserved words in the configuration file is unimportant, but elsewhere, the case is
preserved.
Blank lines and comments are permitted (even encouraged) in the configuration file. A comment begins
with a ``#'' character and finishes at the end of the line. A line may be continued by ensuring that the
last character on the line is a ``\'' (backslash). A comment on a continued line ends at the end of the
continued line. Spaces may be included in lexical elements by enclosing the entire element in double
quotes. A double quote preceded by a backslash is always a literal double quote. A ``#'' in double
quotes or preceded by a backslash is treated literally rather than as a comment delimiter. Lexical
elements and separators are described further in the following sections.
AGENT CONFIGURATION
Each line of the agent configuration section of the configuration file contains details of how to connect
pmcd to one of its agents and specifies which metrics domain the agent deals with. An agent may be
attached as a DSO, or via a socket, or a pair of pipes.
Each line of the agent configuration section of the configuration file must be either an agent
specification, a comment, or a blank line. Lexical elements are separated by whitespace characters,
however a single agent specification may not be broken across lines unless a backslash is used to
continue the line.
Each agent specification must start with a textual label (string) followed by an integer in the range 1
to 510. The label is a tag used to refer to the agent and the integer specifies the domain for which the
agent supplies data. This domain identifier corresponds to the domain portion of the PMIDs handled by
the agent. Each agent must have a unique label and domain identifier.
For DSO agents a line of the form:
label domain-no dso entry-point path
should appear. Where,
label is a string identifying the agent
domain-no is an unsigned integer specifying the agent's domain in the range 1 to 510
entry-point is the name of an initialization function which will be called when the DSO is loaded
path designates the location of the DSO and this is expected to be an absolute pathname. pmcd
is only able to load DSO agents that have the same simabi (Subprogram Interface Model ABI,
or calling conventions) as it does (i.e. only one of the simabi versions will be
applicable). The simabi version of a running pmcd may be determined by fetching
pmcd.simabi. Alternatively, the file(1) command may be used to determine the simabi
version from the pmcd executable.
For a relative path the environment variable PMCD_PATH defines a colon (:) separated list
of directories to search when trying to locate the agent DSO. The default search path is
$PCP_SHARE_DIR/lib:/usr/pcp/lib.
For agents providing socket connections, a line of the form
label domain-no socket addr-family address [ command ]
should appear. Where,
label is a string identifying the agent
domain-no is an unsigned integer specifying the agent's domain in the range 1 to 510
addr-family designates whether the socket is in the AF_INET, AF_INET6 or AF_UNIX domain, and the
corresponding values for this parameter are inet, ipv6 and unix respectively.
address specifies the address of the socket within the previously specified addr-family. For unix
sockets, the address should be the name of an agent's socket on the local host (a valid
address for the UNIX domain). For inet and ipv6 sockets, the address may be either a port
number or a port name which may be used to connect to an agent on the local host. There is
no syntax for specifying an agent on a remote host as a pmcd deals only with agents on the
same machine.
command is an optional parameter used to specify a command line to start the agent when pmcd
initializes. If command is not present, pmcd assumes that the specified agent has already
been created. The command is considered to start from the first non-white character after
the socket address and finish at the next newline that isn't preceded by a backslash.
After a fork(2) the command is passed unmodified to execve(2) to instantiate the agent.
For agents interacting with the pmcd via stdin/stdout, a line of the form:
label domain-no pipe protocol command
should appear. Where,
label is a string identifying the agent
domain-no is an unsigned integer specifying the agent's domain
protocol The value for this parameter should be binary.
Additionally, the protocol can include the notready keyword to indicate that the agent must
be marked as not being ready to process requests from pmcd. The agent will explicitly
notify the pmcd when it is ready to process the requests by sending a PM_ERR_PMDAREADY PDU.
For further details of this protocol, including a description of the IPC parameters that
can be specified in a PMDA Install script with the ipc_prot parameter, see the relevant
section in PMDA(3).
command specifies a command line to start the agent when pmcd initializes. Note that command is
mandatory for pipe-based agents. The command is considered to start from the first non-
white character after the protocol parameter and finish at the next newline that isn't
preceded by a backslash. After a fork(2) the command is passed unmodified to execve(2) to
instantiate the agent.
ACCESS CONTROL CONFIGURATION
The access control section of the configuration file is optional, but if present it must follow the agent
configuration data. The case of reserved words is ignored, but elsewhere case is preserved. Lexical
elements in the access control section are separated by whitespace or the special delimiter characters:
square brackets (``['' and ``]''), braces (``{'' and ``}''), colon (``:''), semicolon (``;'') and comma
(``,''). The special characters are not treated as special in the agent configuration section. Lexical
elements may be quoted (double quotes) as necessary.
The access control section of the file must start with a line of the form:
[access]
In addition to (or instead of) the access section in the pmcd configuration file, access control
specifications are also read from a file having the same name as the pmcd configuration file, but with
'.access' appended to the name. This optional file must not contain the [access] keyword.
Leading and trailing whitespace may appear around and within the brackets and the case of the access
keyword is ignored. No other text may appear on the line except a trailing comment.
Following this line, the remainder of the configuration file should contain lines that allow or disallow
operations from particular hosts or groups of hosts.
There are two kinds of operations that occur via pmcd:
fetch allows retrieval of information from pmcd. This may be information about a metric (e.g.
its description, instance domain, labels or help text) or a value for a metric. See
pminfo(1) for further information.
store allows pmcd to be used to store metric values in agents that permit store operations.
This may be the actual value of the metric (e.g. resetting a counter to zero).
Alternatively, it may be a value used by the PMDA to introduce a change to some aspect of
monitoring of that metric (e.g. server side event filtering) - possibly even only for the
active client tool performing the store operation, and not others. See pmstore(1) for
further information.
Access to pmcd can be granted in three ways - by user, group of users, or at a host level. In the
latter, all users on a host are granted the same level of access, unless the user or group access control
mechanism is also in use.
User names and group names will be verified using the local /etc/passwd and /etc/groups files (or an
alternative directory service), using the getpwent(3) and getgrent(3) routines.
Hosts may be identified by name, IP address, IPv6 address or by the special host specifications
``"unix:"'' or ``"local:"''. ``"unix:"'' refers to pmcd's unix domain socket, on supported platforms.
``"local:"'' is equivalent to specifying ``"unix:"'' and ``localhost``.
Wildcards may also be specified by ending the host identifier with the single wildcard character ``*'' as
the last-given component of an address. The wildcard ``".*"'' refers to all inet (IPv4) addresses. The
wildcard ``":*"'' refers to all IPv6 addresses. If an IPv6 wildcard contains a ``::'' component, then
the final ``*'' refers to the final 16 bits of the address only, otherwise it refers to the remaining
unspecified bits of the address.
The wildcard ``*'' refers to all users, groups or host addresses, including ``"unix:"''. Names of users,
groups or hosts may not be wildcarded.
The following are all valid host identifiers:
boing
localhost
giggle.melbourne.sgi.com
129.127.112.2
129.127.114.*
129.*
.*
fe80::223:14ff:feaf:b62c
fe80::223:14ff:feaf:*
fe80:*
:*
"unix:"
"local:"
*
The following are not valid host identifiers:
*.melbourne
129.127.*.*
129.*.114.9
129.127*
fe80::223:14ff:*:*
fe80::223:14ff:*:b62c
fe80*
The first example is not allowed because only (numeric) IP addresses may contain a wildcard. The second
and fifth examples are not valid because there is more than one wildcard character. The third and sixth
contain an embedded wildcard, the fourth and seventh have a wildcard character that is not the last
component of the address (the last components are 127* and fe80* respectively).
The name localhost is given special treatment to make the behavior of host wildcarding consistent.
Rather than being 127.0.0.1 and ::1, it is mapped to the primary inet and IPv6 addresses associated with
the name of the host on which pmcd is running. Beware of this when running pmcd on multi-homed hosts.
Access for users, groups or hosts are allowed or disallowed by specifying statements of the form:
allow users userlist : operations ;
disallow users userlist : operations ;
allow groups grouplist : operations ;
disallow groups grouplist : operations ;
allow hosts hostlist : operations ;
disallow hosts hostlist : operations ;
list userlist, grouplist and hostlist are comma separated lists of one or more users, groups or
host identifiers.
operations is a comma separated list of the operation types described above, all (which
allows/disallows all operations), or all except operations (which allows/disallows all
operations except those listed).
Either plural or singular forms of users, groups, and hosts keywords are allowed. If this keyword is
omitted, a default of hosts will be used. This behaviour is for backward-compatibility only, it is
preferable to be explicit.
Where no specific allow or disallow statement applies to an operation, the default is to allow the
operation from all users, groups and hosts. In the trivial case when there is no access control section
in the configuration file, all operations from all users, groups, and hosts are permitted.
If a new connection to pmcd is attempted by a user, group or host that is not permitted to perform any
operations, the connection will be closed immediately after an error response PM_ERR_PERMISSION has been
sent to the client attempting the connection.
Statements with the same level of wildcarding specifying identical hosts may not contradict each other.
For example if a host named clank had an IP address of 129.127.112.2, specifying the following two rules
would be erroneous:
allow host clank : fetch, store;
disallow host 129.127.112.2 : all except fetch;
because they both refer to the same host, but disagree as to whether the fetch operation is permitted
from that host.
Statements containing more specific host specifications override less specific ones according to the
level of wildcarding. For example a rule of the form
allow host clank : all;
overrides
disallow host 129.127.112.* : all except fetch;
because the former contains a specific host name (equivalent to a fully specified IP address), whereas
the latter has a wildcard. In turn, the latter would override
disallow host * : all;
It is possible to limit the number of connections from a user, group or host to pmcd. This may be done
by adding a clause of the form
maximum n connections
to the operations list of an allow statement. Such a clause may not be used in a disallow statement.
Here, n is the maximum number of connections that will be accepted from the user, group or host matching
the identifier(s) used in the statement.
An access control statement with a list of user, group or host identifiers is equivalent to a set of
access control statements, with each specifying one of the identifiers in the list and all with the same
access controls (both permissions and connection limits). A group should be used if you want users to
contribute to a shared connection limit. A wildcard should be used if you want hosts to contribute to a
shared connection limit.
When a new client requests a connection, and pmcd has determined that the client has permission to
connect, it searches the matching list of access control statements for the most specific match
containing a connection limit. For brevity, this will be called the limiting statement. If there is no
limiting statement, the client is granted a connection. If there is a limiting statement and the number
of pmcd clients with user ID, group ID, or IP addresses that match the identifier in the limiting
statement is less than the connection limit in the statement, the connection is allowed. Otherwise the
connection limit has been reached and the client is refused a connection.
Group access controls and the wildcarding in host identifiers means that once pmcd actually accepts a
connection from a client, the connection may contribute to the current connection count of more than one
access control statement - the client's host may match more than one access control statement, and
similarly the user ID may be in more than one group. This may be significant for subsequent connection
requests.
Note that pmcd enters a mode where it runs effectively with a higher-level of security as soon as a user
or group access control section is added to the configuration. In this mode only authenticated
connections are allowed - either from a SASL authenticated connection, or a Unix domain socket (which
implicitly passes client credentials). This is the same mode that is entered explicitly using the -S
option. Assuming permission is allowed, one can determine whether pmcd is running in this mode by
querying the value of the pmcd.feature.creds_required metric.
Note also that because most specific match semantics are used when checking the connection limit, for the
host-based access control case, priority is given to clients with more specific host identifiers. It is
also possible to exceed connection limits in some situations. Consider the following:
allow host clank : all, maximum 5 connections;
allow host * : all except store, maximum 2 connections;
This says that only 2 client connections at a time are permitted for all hosts other than "clank", which
is permitted 5. If a client from host "boing" is the first to connect to pmcd, its connection is checked
against the second statement (that is the most specific match with a connection limit). As there are no
other clients, the connection is accepted and contributes towards the limit for only the second statement
above. If the next client connects from "clank", its connection is checked against the limit for the
first statement. There are no other connections from "clank", so the connection is accepted. Once this
connection is accepted, it counts towards both statements' limits because "clank" matches the host
identifier in both statements. Remember that the decision to accept a new connection is made using only
the most specific matching access control statement with a connection limit. Now, the connection limit
for the second statement has been reached. Any connections from hosts other than "clank" will be
refused.
If instead, pmcd with no clients saw three successive connections arrived from "boing", the first two
would be accepted and the third refused. After that, if a connection was requested from "clank" it would
be accepted. It matches the first statement, which is more specific than the second, so the connection
limit in the first is used to determine that the client has the right to connect. Now there are 3
connections contributing to the second statement's connection limit. Even though the connection limit
for the second statement has been exceeded, the earlier connections from "boing" are maintained. The
connection limit is only checked at the time a client attempts a connection rather than being re-
evaluated every time a new client connects to pmcd.
This gentle scheme is designed to allow reasonable limits to be imposed on a first come first served
basis, with specific exceptions.
As illustrated by the example above, a client's connection is honored once it has been accepted.
However, pmcd reconfiguration (see the next section) re-evaluates all the connection counts and will
cause client connections to be dropped where connection limits have been exceeded.
AGENT FENCING
Preventing sampling during the life of a PMDA is sometimes desirable, for example if that sampling
impacts on sensitive phases of a scheduled job. A temporary ``fence'' can be raised to block all PMAPI
client access to one or more agents in this situation. This functionality is provided by the built-in
PMCD PMDA and the pmstore(1) command, as in
# pmstore -i nfsclient,kvm pmcd.agent.fenced 1
If the optional comma-separated list of agent names is omitted, all agents will be fenced. To resume
normal operation, the ``fence'' can be lowered as follows
# pmstore -i nfsclient,kvm pmcd.agent.fenced 0
Lowering the fence for all PMDAs at once is performed using
# pmstore pmcd.agent.fenced 0
Elevated privileges are required to store to the pmcd.agent.fenced metric. For additional information,
see the help text associated with this metric, which can be accessed using the -T, --helptext option to
pminfo(1).
RECONFIGURING PMCD
If the configuration file has been changed or if an agent is not responding because it has terminated or
the PMNS has been changed, pmcd may be reconfigured by sending it a SIGHUP, as in
# pmsignal -a -s HUP pmcd
When pmcd receives a SIGHUP, it checks the configuration file for changes. If the file has been
modified, it is reparsed and the contents become the new configuration. If there are errors in the
configuration file, the existing configuration is retained and the contents of the file are ignored.
Errors are reported in the pmcd log file.
It also checks the PMNS file and any labels files for changes. If any of these files have been modified,
then the PMNS and/or context labels are reloaded. Use of tail(1) on the log file is recommended while
reconfiguring pmcd.
If the configuration for an agent has changed (any parameter except the agent's label is different), the
agent is restarted. Agents whose configurations do not change are not restarted. Any existing agents
not present in the new configuration are terminated. Any deceased agents are that are still listed are
restarted.
Sometimes it is necessary to restart an agent that is still running, but malfunctioning. Simply stop the
agent (e.g. using SIGTERM from pmsignal(1)), then send pmcd a SIGHUP, which will cause the agent to be
restarted.
STARTING AND STOPPING PMCD
Normally, pmcd is started automatically at boot time and stopped when the system is being brought down.
Under certain circumstances it is necessary to start or stop pmcd manually. To do this one must become
superuser and type
# $PCP_RC_DIR/pmcd start
to start pmcd, or
# $PCP_RC_DIR/pmcd stop
to stop pmcd. Starting pmcd when it is already running is the same as stopping it and then starting it
again.
Sometimes it may be necessary to restart pmcd during another phase of the boot process. Time-consuming
parts of the boot process are often put into the background to allow the system to become available
sooner (e.g. mounting huge databases). If an agent run by pmcd requires such a task to complete before
it can run properly, it is necessary to restart or reconfigure pmcd after the task completes. Consider,
for example, the case of mounting a database in the background while booting. If the PMDA which provides
the metrics about the database cannot function until the database is mounted and available but pmcd is
started before the database is ready, the PMDA will fail (however pmcd will still service requests for
metrics from other domains). If the database is initialized by running a shell script, adding a line to
the end of the script to reconfigure pmcd (by sending it a SIGHUP) will restart the PMDA (if it exited
because it couldn't connect to the database). If the PMDA didn't exit in such a situation it would be
necessary to restart pmcd because if the PMDA was still running pmcd would not restart it.
Normally pmcd listens for client connections on TCP/IP port number 44321 (registered at
http://www.iana.org/). Either the environment variable PMCD_PORT or the -p command line option may be
used to specify alternative port number(s) when pmcd is started; in each case, the specification is a
comma-separated list of one or more numerical port numbers. Should both methods be used or multiple -p
options appear on the command line, pmcd will listen on the union of the set of ports specified via all
-p options and the PMCD_PORT environment variable. If non-default ports are used with pmcd care should
be taken to ensure that PMCD_PORT is also set in the environment of any client application that will
connect to pmcd, or that the extended host specification syntax is used (see PCPIntro(1) for details).
CAVEATS
pmcd does not explicitly terminate its children (agents), it only closes their pipes. If an agent never
checks for a closed pipe it may not terminate.
The configuration file parser will only read lines of less than 1200 characters. This is intended to
prevent accidents with binary files.
The timeouts controlled by the -t option apply to IPC between pmcd and the PMDAs it spawns. This is
independent of settings of the environment variables PMCD_CONNECT_TIMEOUT and PMCD_REQUEST_TIMEOUT (see
PCPIntro(1)) which may be used respectively to control timeouts for client applications trying to connect
to pmcd and trying to receive information from pmcd.
DIAGNOSTICS
If pmcd is already running the message "Error: OpenRequestSocket bind: Address may already be in use"
will appear. This may also appear if pmcd was shutdown with an outstanding request from a client. In
this case, a request socket has been left in the TIME_WAIT state and until the system closes it down
(after some timeout period) it will not be possible to run pmcd.
In addition to the standard PCP debugging flags, see pmdbg(1), pmcd currently uses the options: appl0 for
tracing I/O and termination of agents, appl1 for tracing access control and appl2 for tracing the
configuration file scanner and parser.
FILES
$PCP_PMCDCONF_PATH
default configuration file
$PCP_PMCDCONF_PATH.access
optional access control specification file
$PCP_PMCDOPTIONS_PATH
command line options to pmcd when launched from $PCP_RC_DIR/pmcd All the command line option lines
should start with a hyphen as the first character.
$PCP_SYSCONFIG_DIR/pmcd
Environment variables that will be set when pmcd executes. Only settings of the form
"PMCD_VARIABLE=value" or "PCP_VARIABLE=value" are honoured.
$PCP_SYSCONF_DIR/labels.conf
settings related to labels used globally throughout the PMCS.
$PCP_SYSCONF_DIR/labels
directory of files containing the global metric labels that will be set for every client context
created by pmcd. File names starting with a ``.'' are ignored, and files ending in ``.json'' are
``JSONB'' formatted name:value pairs. The merged set can be queried via the pmcd.labels metric.
Context labels are applied universally to all metrics.
$PCP_SYSCONF_DIR/labels/optional
directory of files containing the global metric labels that will be set for every client context
created by pmcd, but which are flagged as optional. These labels are exactly the same as other
context labels except that they are not used in time series identifier calculations.
./pmcd.log
(or $PCP_LOG_DIR/pmcd/pmcd.log when started automatically)
All messages and diagnostics are directed here.
$PCP_RUN_DIR/pmcd.pid
contains an ascii decimal representation of the process ID of pmcd, when it's running.
/etc/pcp/tls.conf
OpenSSL certificate configuration information file, used for optional Secure Socket Layer
connections.
/etc/passwd
user names, user identifiers and primary group identifiers, used for access control specifications
/etc/groups
group names, group identifiers and group members, used for access control specifications
ENVIRONMENT
The following variables are set in $PCP_SYSCONFIG_DIR/pmcd.
In addition to the PCP environment variables described in the PCP ENVIRONMENT section below, the
PMCD_PORT variable is also recognised as the TCP/IP port for incoming connections (default 44321), and
the PMCD_SOCKET variable is also recognised as the path to be used for the Unix domain socket.
If set to the value 1, the PMCD_LOCAL environment variable will cause pmcd to run in a localhost-only
mode of operation, where it binds only to the loopback interface. The pmcd.feature.local metric can be
queried to determine if pmcd is running in this mode.
The PMCD_MAXPENDING variable can be set to indicate the maximum length to which the queue of pending
client connections may grow.
The PMCD_ROOT_AGENT variable controls whether or not pmcd or pmdaroot (when available), start subsequent
pmdas. When set to a non-zero value, pmcd will opt to have pmdaroot start, and stop, PMDAs.
The PMCD_RESTART_AGENTS variable determines the behaviour of pmcd in the presence of child PMDAs that
have been observed to exit (this is a typical response in the presence of very large, usually domain-
induced, PDU latencies). When set to a non-zero value, pmcd will attempt to restart such PMDAS once
every minute. When set to zero, it uses the original behaviour of just logging the failure.
PCP ENVIRONMENT
Environment variables with the prefix PCP_ are used to parameterize the file and directory names used by
PCP. On each installation, the file /etc/pcp.conf contains the local values for these variables. The
$PCP_CONF variable may be used to specify an alternative configuration file, as described in pcp.conf(5).
For environment variables affecting PCP tools, see pmGetOptions(3).
SEE ALSO
PCPIntro(1), pmdbg(1), pmerr(1), pmgenmap(1), pminfo(1), pmrep(1), pmstat(1), pmstore(1), pmval(1),
getpwent(3), getgrent(3), labels.conf(5), pcp.conf(5), pcp.env(5) and PMNS(5).