NAME
vnStatd - the alternative for cron based updating
SYNOPSIS
vnstatd [ -Ddnpsv? ] [ --config file ] [ --daemon ] [ --debug ] [
--help ] [ --nodaemon ] [ --pidfile file ] [ --sync ] [ --version ]
DESCRIPTION
The purpose of vnstatd is to provide a more flexible way for updating
vnstat(1) databases than what using cron for updating can provide. The
daemon makes possible updating databases more often but at the same
time requires less disk access since data can be cached and written
only later to disk at a user configurable interval. It is also able to
track how interfaces come and go without the need of additional scripts
that are required with cron based updates.
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 to a user selectable file or using
syslog.
Once started, the daemon will check if there are any databases
available in the database directory that has been specified in the
configuration file and exit if no databases can be found. The reason
for this behaviour is to avoid starting the daemon when it’s clear that
it wouldn’t have anything to do.
OPTIONS
--config file
Use file as config file instead of using normal config file
search function.
-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.
-n, --nodaemon
Stay in foreground attached to the current terminal and start
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.
-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 enought time has passed since the
daemon was previously running or if the internal counters are
clearly out of sync.
-v, --version
Show current version.
-?, --help
Show a command 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
updated. This is similar to the run interval for alternative cron
based updating. However, the difference is that the data doesn’t 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 20, SaveInterval 5 and
PollInterval 2 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 rised 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 rised 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 will not be updated even
if it’s configuration setting has been changed.
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. Files are named according to the
monitored interfaces.
/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.log
Log file that will be used if logging to file is enable and no
other file is specified in the config file.
/var/run/vnstat.pid
File used for storing the process id if no other file is
specified in the configuration file or using the command line
parameter.
RESTRICTIONS
Updates needs to be executed at least as often as it is possible for
the interface to generate enough traffic to wrap 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 working solution.
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>
SEE ALSO
vnstat(1), vnstati(1), vnstat.conf(5), signal(7)