Ubuntu Manpage: vnstatd - daemon based database updating for vnStat

NAME

       vnstatd - daemon based database updating for vnStat

SYNOPSIS

       vnstatd  [-Ddnpsv?]   [--alwaysadd]  [--config  file]  [--daemon]  [--debug]  [-g  group] [--group group]
       [--help] [--noadd] [--nodaemon] [--pidfile file] [--sync] [--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 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 --alwaysadd option.

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.

OPTIONS

--alwaysadd
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 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.

--noadd
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 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 enough time has passed since the daemon was previously running or if the internal counters are
clearly out of sync.

-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.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.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 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 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 a shorter
       update interval 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 being aliased.

AUTHOR

       Teemu Toivola <tst at iki dot fi>