start-stop-daemon(8) — Linux manual page


start-stop-daemon(8)           dpkg suite           start-stop-daemon(8)

NAME         top

       start-stop-daemon - start and stop system daemon programs

SYNOPSIS         top

       start-stop-daemon [option...] command

DESCRIPTION         top

       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 --pid or --pidfile are 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, parent pid, 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.

COMMANDS         top

       -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.

       -K, --stop
           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.

       -T, --status
           Check for the existence of a specified process, and returns
           an exit status code, according to the LSB Init Script Actions
           (since version 1.16.1).

       -H, --help
           Show usage information and exit.

       -V, --version
           Show the program version and exit.

OPTIONS         top

   Matching options
       --pid pid
           Check for a process with the specified pid (since version
           1.17.6).  The pid must be a number greater than 0.

       --ppid ppid
           Check for a process with the specified parent pid ppid (since
           version 1.17.7).  The ppid must be a number greater than 0.

       -p, --pidfile pidfile
           Check whether a process has created the file pidfile.

           Note: Using this matching option alone might cause unintended
           processes to be acted on, if the old process terminated
           without being able to remove the pidfile.

           Warning: Using this match option with a world-writable
           pidfile or using it alone with a daemon that writes the
           pidfile as an unprivileged (non-root) user will be refused
           with an error (since version 1.19.3) as this is a security
           risk, because either any user can write to it, or if the
           daemon gets compromised, the contents of the pidfile cannot
           be trusted, and then a privileged runner (such as an init
           script executed as root) would end up acting on any system
           process.  Using /dev/null is exempt from these checks.

       -x, --exec executable
           Check for processes that are instances of this executable.
           The executable argument should be an absolute pathname.

           Note: This might not work as intended with interpreted
           scripts, as the executable will point to the interpreter.
           Take into account processes running from inside a chroot will
           also be matched, so other match restrictions might be needed.

       -n, --name process-name
           Check for processes with the name process-name.  The process-
           name is usually the process filename, but it could have been
           changed by the process itself.

           Note: On most systems this information is retrieved from the
           process comm name from the kernel, which tends to have a
           relatively short length limit (assuming more than 15
           characters is non-portable).

       -u, --user username|uid
           Check for processes owned by the user specified by username
           or uid.

           Note: Using this matching option alone will cause all
           processes matching the user to be acted on.

   Generic options
       -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

           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.

       -t, --test
           Print actions that would be taken and set appropriate return
           value, but take no action.

       -o, --oknodo
           Return exit status 0 instead of 1 if no actions are (would
           be) taken.

       -q, --quiet
           Do not print informational messages; only display error

       -c, --chuid username|uid[:group|gid]
           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(1) 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
           Change directory and chroot to root before starting the
           process.  Please note that the pidfile is also written after
           the chroot.

       -d, --chdir path
           Change directory 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 change directory
           to the root directory before starting the process.

       -b, --background
           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.

           Wait for the background process to send a readiness
           notification before considering the service started (since
           version 1.19.3).  This implements parts of the systemd
           readiness protocol, as specified in the sd_notify(3) manual
           page.  The following variables are supported:

               The program is ready to give service, so we can exit

               The program requests to extend the timeout by number
               microseconds.  This will reset the current timeout to the
               specified value.

               The program is exiting with an error.  Do the same and
               print the user-friendly string for the errno value.

       --notify-timeout timeout
           Set a timeout for the --notify-await option (since version
           1.19.3).  When the timeout is reached, start-stop-daemon will
           exit with an error code, and no readiness notification will
           be awaited.  The default is 60 seconds.

       -C, --no-close
           Do not close any file descriptor when forcing the daemon into
           the background (since version 1.16.5).  Used for debugging
           purposes to see the process output, or to redirect file
           descriptors to log the process output.  Only relevant when
           using --background.

       -O, --output pathname
           Redirect stdout and stderr to pathname when forcing the
           daemon into the background (since version 1.20.6).  Only
           relevant when using --background.

       -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 (since version 1.15.0).  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.

           This option might do nothing on some systems, where POSIX
           process scheduling is not supported.

       -I, --iosched class:priority
           This alters the IO scheduler class and priority of the
           process before starting it (since version 1.15.0).  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-

           This option might do nothing on some systems, where Linux IO
           scheduling is not supported.

       -k, --umask mask
           This sets the umask of the process before starting it (since
           version 1.13.22).

       -m, --make-pidfile
           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 only be
           removed when stopping the program if --remove-pidfile is

           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.

           Used when stopping a program that does not remove its own pid
           file (since version 1.17.19).  This option will make start-
           stop-daemon remove the file referenced with --pidfile after
           terminating the process.

       -v, --verbose
           Print verbose informational messages.

EXIT STATUS         top

       0   The requested action was performed.  If --oknodo was
           specified, it's also possible that nothing had to be done.
           This can happen when --start was specified and a matching
           process was already running, or when --stop was specified and
           there were no matching processes.

       1   If --oknodo was not specified and nothing was done.

       2   If --stop and --retry were specified, but the end of the
           schedule was reached and the processes were still running.

       3   Any other error.

       When using the --status command, the following status codes are

       0   Program is running.

       1   Program is not running and the pid file exists.

       3   Program is not running.

       4   Unable to determine program status.

EXAMPLE         top

       Start the food daemon, unless one is already running (a process
       named food, running as user food, with pid in

        start-stop-daemon --start --oknodo --user food --name food \
          --pidfile /usr/local/var/run/ --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 /usr/local/var/run/ --retry 5

       Demonstration of a custom schedule for stopping food:

        start-stop-daemon --stop --oknodo --user food --name food \
          --pidfile /usr/local/var/run/ --retry=TERM/30/KILL/5

COLOPHON         top

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1.22.6-77-g86fe7               2024-03-10           start-stop-daemon(8)