NAME

supervise-daemon — starts a daemon and restarts it if it crashes

SYNOPSIS

DESCRIPTION

supervise-daemon provides a consistent method of starting, stopping and restarting daemons. If -K, --stop or -s, --signal is not provided, then we assume we are starting the daemon. supervise-daemon only works with daemons which do not fork. If your daemon has options to tell it not to fork, it should be configured to not fork.

Here are the options to specify the daemon and how it should start or stop:

-u, --user user[:group]

Start the daemon as the user and update $HOME accordingly or stop daemons owned by the user. You can optionally append a group name here also.

-v, --verbose

Print the action(s) that are taken just before doing them.

The options are as follows:

-a, --healthcheck-timer seconds

Run the healthcheck() command, possibly followed by the unhealthy() command every time this number of seconds passes.

-A, --healthcheck-delay seconds

Wait this long before the first health check.

-D, --respawn-delay seconds

Wait this number of seconds before restarting a daemon after it crashes. The default is 0.

-d, --chdir path

chdir to this directory before starting the daemon.

-e, --env VAR=VALUE

Set the environment variable VAR to VALUE.

-g, --group group

Start the daemon as in the group.

-I, --ionice class[:data]

Modifies the IO scheduling priority of the daemon. Class can be 0 for none, 1 for real time, 2 for best effort and 3 for idle. Data can be from 0 to 7 inclusive.

-k, --umask mode

Set the umask of the daemon.

-m, --respawn-max count

Sets the maximum number of times a daemon will be respawned. If a daemon crashes more than this number of times, supervise-daemon will give up and exit. The default is 10 and 0 means unlimited.

If respawn-period is also set, more than respawn-max crashes must occur during respawn-period seconds to cause supervise-daemon to give up and exit.

-N, --nicelevel level

Modifies the scheduling priority of the daemon.

-P, --respawn-period seconds

Sets the length of a respawn period. See the description of --respawn-max for more information.

-R, --retry timeout | signal/timeout

The retry specification can be either a timeout in seconds or multiple signal/timeout pairs (like SIGTERM/5). If this option is not given, the default is SIGTERM/5.

-r, --chroot path

chroot to this directory before starting the daemon. All other paths, such as the path to the daemon and chdir should be relative to the chroot.

-, --signal signal

Instruct a supervisor to signal the process it is supervising. The process to communicate with is determined by the name of the service taken from the RC_SVCNAME environment variable.

-u, --user user

Start the daemon as the specified user.

-1, --stdout logfile

Redirect the standard output of the process to logfile. Must be an absolute pathname, but relative to the path optionally given with -r, --chroot. The logfile can also be a named pipe.

-2, --stderr logfile

The same thing as -1, --stdout but with the standard error output.

ENVIRONMENT

SSD_NICELEVEL can also set the scheduling priority of the daemon, but the command line option takes precedence.

NOTE

supervise-daemon uses getopt(3) to parse its options, which allows it to accept the `--' option which will cause it to stop processing options at that point. Any subsequent arguments are passed as arguments to the daemon to start and used when finding a daemon to stop or signal.

NOTE

If respawn-delay, respawn-max and respawn-period are not set correctly, it is possible to trigger a situation in which the supervisor will infinitely try to respawn a daemon. To avoid this, if you change the values of --respawn-delay, --respawn-max or --respawn-period, always make sure the settings mmake sense. For example, a respawn period of 5 seconds with a respawn max of 10 and a respawn delay of 1 second leads to infinite respawning since there can never be 10 respawns within 5 seconds.

NOTE

Invoking supervise-daemon requires both the RC_SVCNAME environment variable to be set and the name of the service as the first argument on the command line, so it is best to invoke it inside a service script rather than manually.

SEE ALSO

chdir(2), chroot(2), getopt(3), nice(2),

HISTORY

supervise-daemon first appeared in Debian.

This is a complete re-implementation with the process finding code in the OpenRC library (librc, -lrc) so other programs can make use of it.

AUTHORS

William Hubbs <w.d.hubbs@gmail.com>