vnstatd - daemon based database updating for vnStat
] [-g group
] [--pidfile file
] [--user user
The purpose of vnstatd
is to provide a more flexible and robust way for
(1) the database than what using cron for updating can
provide. The daemon makes possible updating the database more often but at the
same time causes less disk access since data can be cached and written only
later to disk at a user configurable interval. 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
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 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, it is possible to allow the daemon to create new
database entries whenever previously unseen interfaces become visible using
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.
- Enable automatic creation of new database entries for previously unseen
interfaces even if the database directory already contains a database 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 excluded from getting added.
- --config file
- Use file as configuration file instead of using normal
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.
- Disable automatic creation of new database entries for all available
interfaces if the daemon is started with no database found. Pseudo
interfaces lo, lo0 and sit0 are excluded from getting added.
- -n, --nodaemon
- Stay in foreground attached to the current terminal and start the update
- -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
- -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
- -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.
The behaviour of the daemon is configured mainly using the configuration
keywords UpdateInterval, PollInterval
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.
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
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
maximum value of 60 minutes.
The default values of UpdateInterval
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
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.
The daemon is listening to signals SIGHUP, SIGINT
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.
signals will cause the daemon to write all
cached data to disk and then exit.
- Default database directory.
- Config file that will be used unless $HOME/.vnstatrc exists. See
the configuration chapter and vnstat.conf(5) for more information.
- Log file that will be used if logging to file is enable and no other file
is specified in the config file.
- File used for storing the process id if no other file is specified in the
configuration file or using the command line parameter.
Updates needs 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. This isn't
an issue for 64-bit kernels but at least one update every hour is always
required in order to provide proper input. With 32-bit kernels, the maximum
time between two updates depends on how fast the interface can transfer 4 GiB.
Calculated theoretical times are:
|10 Mbit: 54 minutes
|100 Mbit: 5 minutes
|1000 Mbit: 30 seconds
However, for 1000 Mbit interfaces updating once every minute is usually a usable
solution if faster updates can't be used.
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
Teemu Toivola <tst at iki dot fi>