start−stop−daemon − start and stop system daemon programs
start−stop−daemon [options] command
start−stop−daemon is used to control the creation and termination of system-level processes. Using one of the matching options, start−stop−daemon can be configured to find existing instances of a running process.
Note: unless −−pidfile is specified, start−stop−daemon behaves similar to killall(1). start−stop−daemon will scan the process table looking for any processes which match the process name, uid, and/or gid (if specified). Any matching process will prevent −−start from starting the daemon. All matching processes will be sent the TERM signal (or the one specified via −−signal or −−retry) if −−stop is specified. For daemons which have long-lived children which need to live through a −−stop, you must specify a pidfile.
−S, −−start [−−] arguments
Check for the existence of a specified process. If such a process exists, start−stop−daemon does nothing, and exits with error status 1 (0 if −−oknodo is specified). If such a process does not exist, it starts an instance, using either the executable specified by −−exec or, if specified, by −−startas. Any arguments given after −− on the command line are passed unmodified to the program being started.
Checks for the existence of a specified process. If such a process exists, start−stop−daemon sends it the signal specified by −−signal, and exits with error status 0. If such a process does not exist, start−stop−daemon exits with error status 1 (0 if −−oknodo is specified). If −−retry is specified, then start−stop−daemon will check that the process(es) have terminated.
Show usage information and exit.
Show the program version and exit.
−p, −−pidfile pid-file
Check whether a process has created the file pid-file.
−x, −−exec executable
Check for processes that are instances of this executable (according to /proc/pid/exe).
−n, −−name process-name
Check for processes with the name process-name (according to /proc/pid/stat).
−u, −−user username|uid
Check for processes owned by the user specified by username or uid.
−g, −−group group|gid
Change to group or gid when starting the process.
−s, −−signal signal
With −−stop, specifies the signal to send to processes being stopped (default TERM).
−R, −−retry timeout|schedule
With −−stop, specifies that start−stop−daemon is to check whether the process(es) do finish. It will check repeatedly whether any matching processes are running, until none are. If the processes do not exit it will then take further action as determined by the schedule.
If timeout is specified instead of schedule, then the schedule signal/timeout/KILL/timeout is used, where signal is the signal specified with −−signal.
schedule is a list of at least two items separated by slashes (/); each item may be −signal-number or [−]signal-name, which means to send that signal, or timeout, which means to wait that many seconds for processes to exit, or forever, which means to repeat the rest of the schedule forever if necessary.
If the end of the schedule is reached and forever is not specified, then start−stop−daemon exits with error status 2. If a schedule is specified, then any signal specified with −−signal is ignored.
−a, −−startas pathname
With −−start, start the process specified by pathname. If not specified, defaults to the argument given to −−exec.
Print actions that would be taken and set appropriate return value, but take no action.
Return exit status 0 instead of 1 if no actions are (would be) taken.
Do not print informational messages; only display error messages.
−c, −−chuid username|uid
Change to this username/uid before starting the process. You can also specify a group by appending a :, then the group or gid in the same way as you would for the ‘chown’ command (user:group). If a user is specified without a group, the primary GID for that user is used. When using this option you must realize that the primary and supplemental groups are set as well, even if the −−group option is not specified. The −−group option is only for groups that the user isn’t normally a member of (like adding per process group membership for generic users like nobody).
−r, −−chroot root
Chdir and chroot to root before starting the process. Please note that the pidfile is also written after the chroot.
−d, −−chdir path
Chdir to path before starting the process. This is done after the chroot if the −r|−−chroot option is set. When not specified, start−stop−daemon will chdir to the root directory before starting the process.
Typically used with programs that don’t detach on their own. This option will force start−stop−daemon to fork before starting the process, and force it into the background. WARNING: start−stop−daemon cannot check the exit status if the process fails to execute for any reason. This is a last resort, and is only meant for programs that either make no sense forking on their own, or where it’s not feasible to add the code for them to do this themselves.
−N, −−nicelevel int
This alters the priority of the process before starting it.
−P, −−procsched policy:priority
This alters the process scheduler policy and priority of the process before starting it. The priority can be optionally specified by appending a : followed by the value. The default priority is 0. The currently supported policy values are other, fifo and rr.
−I, −−iosched class:priority
This alters the IO scheduler class and priority of the process before starting it. The priority can be optionally specified by appending a : followed by the value. The default priority is 4, unless class is idle, then priority will always be 7. The currently supported values for class are idle, best-effort and real-time.
−k, −−umask mask
This sets the umask of the process before starting it.
Used when starting a program that does not create its own pid file. This option will make start−stop−daemon create the file referenced with −−pidfile and place the pid into it just before executing the process. Note, the file will not be removed when stopping the program. NOTE: This feature may not work in all cases. Most notably when the program being executed forks from its main process. Because of this, it is usually only useful when combined with the −−background option.
Print verbose informational messages.
start−stop−daemon returns 0 if the requested action was performed, or if −−oknodo is specified and either −−start was specified and a matching process was already running, or −−stop was specified and there were no matching processes. If −−oknodo was not specified and nothing was done, 1 is returned. If --stop and --retry were specified, but the end of the schedule was reached and the processes were still running, the error value is 2. For all other errors, the status is 3.
Start the food daemon, unless one is already running (a process named food, running as user food, with pid in food.pid):
start−stop−daemon −−start −−oknodo −−user food −−name food −−pidfile /var/run/food.pid −−startas /usr/sbin/food −−chuid food −− −−daemon
Send SIGTERM to food and wait up to 5 seconds for it to stop:
start−stop−daemon −−stop −−oknodo −−user food −−name food −−pidfile /var/run/food.pid −−retry 5
Demonstration of a custom schedule for stopping food:
start−stop−daemon −−stop −−oknodo −−user food −−name food −−pidfile /var/run/food.pid −−retry=TERM/30/KILL/5
Manual page by Klee Dienes <klee [AT] mit.edu>, partially reformatted by Ian Jackson.