Ubuntu Manpage: vnstatd - daemon based database updating for vnStat

NAME

       vnstatd - daemon based database updating for vnStat

SYNOPSIS

       vnstatd  [-Ddnpstv?]  [--alwaysadd [mode]] [--config file] [--daemon] [--debug] [-g group]
       [--group group] [--help]  [--initdb]  [--noadd]  [--nodaemon]  [--pidfile  file]  [--sync]
       [--timestamp] [--u user] [--user user] [--version]

DESCRIPTION

The purpose of vnstatd is to provide a flexible and robust way for updating the database
that vnstat(1) uses. The availability of each interface is automatically tracked which
removes the need for additional scripts to be implemented and called when an interface
comes online or goes offline.

vnstatd is the command for starting the daemon. The daemon can either fork itself to run
as a background process or stay attached to the terminal. It supports logging directly to
terminal, to a user selectable file or using syslog.

Once started, the daemon will read vnstat.conf(5) if available and then check if there is
a database present in the database directory that has been specified in the configuration
file. By default, if no database is found, a database will be created during startup with
entries for all available interfaces excluding pseudo interfaces lo, lo0 and sit0. This
automatic database entry creation behaviour can be disabled using the --noadd option.
Alternatively, using the --alwaysadd option instructs the daemon to create new database
entries whenever interfaces not currently in the databases become visible.

The daemon will proceed to track the availability of monitored interfaces, process the
interface traffic statistics and write new values to the database at a configured
interval. As a result, the daemon ends up spending most of the time sleeping between
updates.

When the UseUTC configuration option isn't enabled, data is stored in the database using
local time based on the daemon's execution environment when the configuration option isn't
enabled. Any changes in the system clock or the system timezone configuration will result
in data being inserted according to the new local time without any recalculation being
done for already stored data. The daemon and the database in essence aren't aware of the
used timezone or possible daylight saving time and cannot be configured to offset the
timestamps to any direction. If a system clock or system timezone change or daylight
saving time observation ending results in an already seen time period to repeat then the
existing database values get incremented with the new data.

OPTIONS

--alwaysadd [mode]
Enable automatic creation of new database entries for interfaces not currently in
the database even if the database file already exists when the daemon is started.
New database entries will also get created for new interfaces seen while the daemon
is running. Pseudo interfaces lo, lo0 and sit0 are always excluded from getting
added. Using the option without mode defined or with mode set to 1 will enable the
feature. Setting mode to 0 will disable the feature. This command line option
overrides the AlwaysAddNewInterfaces configuration option when used.

--config file
Use file as configuration file instead of using automatic configuration file search
functionality.

-d, --daemon
Fork process to background and run as a daemon.

-D, --debug
Provide additional output for debug purposes. The process will stay attached to the
terminal for output.

-g, --group group
Set daemon process group to group during startup. group can be either the name of
the group or a numerical group id. This option can only be used when the process is
started as root.

--initdb
Create a new empty database without interface data and exit. If the database
already exists then access to it is only verified. The daemon will not stay running
when this option is used. This option cannot be used in combination with -d,
--daemon or -n, --nodaemon.

--noadd
Disable the automatic creation of new database entries for all available interfaces
if the daemon is started with no database found or with a database without any
interfaces. The daemon will fail to start if this option is used when the database
contains no interfaces or doesn't exist. The daemon will create an empty database
if one doesn't already exist. Pseudo interfaces lo, lo0 and sit0 are always
excluded from getting added regardless of this option.

-n, --nodaemon
Stay in foreground attached to the current terminal and start the update process.

-p, --pidfile file
Write the process id to file and use it for locking so that another instance of the
daemon cannot be started if the same file is specified. This option has no effect
if used in combination with -n, --nodaemon.

-s, --sync
Synchronize internal counters in the database with interface counters for all
available interfaces before starting traffic monitoring. Use this option if the
traffic between the previous shutdown and the current startup of the daemon needs
to be ignored. This option isn't required in normal use because the daemon will
automatically synchronize the internal counters after a system reboot, if enough
time has passed since the daemon was previously running or if the internal counters
are clearly out of sync.

-t, --timestamp
Add a timestamp to the beginning of every print from the daemon when the process is
running in the foreground attached to a terminal after having been started with the
-n, --nodaemon option.

-u, --user user
Set daemon process user to user during startup. user can be either the login of
the user or a numerical user id. This option can only be used when the process is
started as root.

-v, --version
Show current version of the daemon executable.

-?, --help
Show a command option summary.

CONFIGURATION

The behaviour of the daemon is configured mainly using the configuration keywords
UpdateInterval, PollInterval and SaveInterval in the configuration file.

UpdateInterval defines in seconds how often the interface data is fetched and updated.
This is similar to the run interval for alternative cron based updating. However, the
difference is that the data doesn't directly get written to disk during updates.

PollInterval defines in seconds how often the list of available interfaces is checked for
possible changes. The minimum value is 2 seconds and the maximum 60 seconds. PollInterval
also defines the resolution for other intervals.

SaveInterval defines in minutes how often cached interface data is written to disk. A
write can only occur during the updating of interface data. Therefore, the value should be
a multiple of UpdateInterval with a maximum value of 60 minutes.

The default values of UpdateInterval 30, SaveInterval 5 and PollInterval 5 are usually
suitable for most systems and provide a similar behaviour as cron based updating does but
with a better resolution for interface changes and fast interfaces.

For embedded and/or low power systems more tuned configurations are possible. In such
cases if the interfaces are mostly static the PollInterval can be increased to around
10-30 seconds and UpdateInterval set to 60 seconds. Higher values up to 300 seconds are
possible if the interface speed is 10 Mbit or less. SaveInterval can be increased for
example to 15, 30 or even 60 minutes depending on how often the data needs to be viewed.

SIGNALS

       The daemon is listening to signals SIGHUP, SIGINT and SIGTERM.  Sending the SIGHUP  signal
       to  the  daemon  will  cause  cached  data to be written to disk, a rescan of the database
       directory and a reload of settings from the configuration  file.  However,  the  pid  file
       location will not be changed even if it's configuration setting has been modified.

       SIGTERM and SIGINT signals will cause the daemon to write all cached data to disk and then
       exit.

FILES

       /var/lib/vnstat/
              Default database directory.

       /etc/vnstat.conf
              Config file that will be used unless $HOME/.vnstatrc exists. See the  configuration
              chapter and vnstat.conf(5) for more information.

       /var/log/vnstat/vnstat.log
              Log  file  that  will  be  used  if  logging to file is enable and no other file is
              specified in the config file.

       /run/vnstat/vnstat.pid
              File used for storing the process id when running as a background process and if no
              other  file  is  specified  in  the  configuration  file  or using the command line
              parameter.

RESTRICTIONS

       Updates need to be executed at least as often as it  is  possible  for  the  interface  to
       generate enough traffic to overflow the kernel interface traffic counter. Otherwise, it is
       possible that some traffic won't be seen. With  32-bit  interface  traffic  counters,  the
       maximum  time  between  two  updates depends on how fast the interface can transfer 4 GiB.
       Note that there is no guarantee that a 64-bit kernel has 64-bit interface traffic counters
       for all interfaces. Calculated theoretical times are:

              10 Mbit:        54 minutes
              100 Mbit:        5 minutes
              1000 Mbit:      30 seconds
       Virtual  and  aliased  interfaces  cannot  be monitored because the kernel doesn't provide
       traffic information for that type of interfaces. Such interfaces are usually named eth0:0,
       eth0:1, eth0:2 etc. where eth0 is the actual interface being aliased.

AUTHOR

       Teemu Toivola <tst at iki dot fi>