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>