openrc/man/supervise-daemon.8

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.Dd April 27, 2016
.Dt supervise-DAEMON 8 SMM
.Os OpenRC
.Sh NAME
.Nm supervise-daemon
.Nd starts a daemon and restarts it if it crashes
.Sh SYNOPSIS
.Nm
.Fl D , -respawn-delay
.Ar seconds
.Fl d , -chdir
.Ar path
.Fl e , -env
.Ar var=value
.Fl g , -group
.Ar group
.Fl I , -ionice
.Ar arg
.Fl k , -umask
.Ar value
.Fl m , -respawn-max
.Ar count
.Fl N , -nicelevel
.Ar level
.Fl p , -pidfile
.Ar pidfile
.Fl P , -respawn-period
.Ar seconds
.Fl r , -chroot
.Ar chrootpath
.Fl u , -user
.Ar user
.Fl 1 , -stdout
.Ar logfile
.Fl 2 , -stderr
.Ar logfile
.Fl S , -start
.Ar daemon
.Op Fl -
.Op Ar arguments
.Nm
.Fl K , -stop
.Ar daemon
.Fl p , -pidfile
.Ar pidfile
.Fl r , -chroot
.Ar chrootpath
.Sh DESCRIPTION
.Nm
provides a consistent method of starting, stopping and restarting
daemons. If
.Fl K , -stop
is not provided, then we assume we are starting the daemon.
.Nm
only works with daemons which do not fork. Also, it uses its own pid
file, so the daemon should not write a pid file, or the pid file passed
to 
.Nm
should not be the one the daemon writes.
.Pp
Here are the options to specify the daemon and how it should start or stop:
.Bl -tag -width indent
.It Fl p , -pidfile Ar pidfile
When starting, we write a
.Ar pidfile
so we know which supervisor to stop.  When stopping we only stop the pid(s)
listed in the
.Ar pidfile .
.It Fl u , -user Ar user Ns Op : Ns Ar group
Start the daemon as the
.Ar user
and update $HOME accordingly or stop daemons
owned by the user. You can optionally append a
.Ar group
name here also.
.It Fl v , -verbose
Print the action(s) that are taken just before doing them.
.Pp
The options are as follows:
.Bl -tag -width indent
.It Fl D , -respawn-delay Ar seconds
wait this number of seconds before restarting a daemon after it crashes.
The default is 0.
.It Fl d , -chdir Ar path
chdir to this directory before starting the daemon.
.It Fl e , -env Ar VAR=VALUE
Set the environment variable VAR to VALUE.
.It Fl g , -group Ar group
Start the daemon as in the group.
.It Fl I , -ionice Ar class Ns Op : Ns Ar 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.
.It Fl k , -umask Ar mode
Set the umask of the daemon.
.It Fl m , -respawn-max Ar count
Sets the maximum number of times a daemon will be respawned during a
respawn period. If a daemon dies more than this number of times during a
respawn period,
.Nm
will give up trying to respawn it and exit. The default is 10, and 0
means unlimited.
.It Fl N , -nicelevel Ar level
Modifies the scheduling priority of the daemon.
.It Fl P , -respawn-period Ar seconds
Sets the length of a respawn period. The default is 10 seconds. See the
description of --respawn-max for more information.
.It Fl r , -chroot Ar path
chroot to this directory before starting the daemon. All other paths, such
as the path to the daemon, chdir and pidfile, should be relative to the chroot.
.It Fl u , -user Ar user
Start the daemon as the specified user.
.It Fl 1 , -stdout Ar logfile
Redirect the standard output of the process to logfile.
Must be an absolute pathname, but relative to the path optionally given with
.Fl r , -chroot .
The logfile can also be a named pipe.
.It Fl 2 , -stderr Ar logfile
The same thing as
.Fl 1 , -stdout
but with the standard error output.
.El
.Sh ENVIRONMENT
.Va SSD_NICELEVEL
can also set the scheduling priority of the daemon, but the command line
option takes precedence.
.Sh NOTE
.Nm
uses
.Xr 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.
.Sh 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.
.Sh SEE ALSO
.Xr chdir 2 ,
.Xr chroot 2 ,
.Xr getopt 3 ,
.Xr nice 2 ,
.Xr rc_find_pids 3
.Sh BUGS
.Nm
cannot stop an interpreted daemon that no longer exists without a pidfile.
.Sh HISTORY
.Nm
first appeared in Debian.
.Pp
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.
.Sh AUTHORS
.An William Hubbs <w.d.hubbs@gmail.com>