start-stop-daemon - start and stop system daemon programs
start-stop-daemon [option...] 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 --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.
- -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.
- --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.
- -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.
- -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 messages.
- -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.
- --notify-await
- 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) man page. The following variables are supported:
- READY=1
- The program is ready to give service, so we can exit safely.
- EXTEND_TIMEOUT_USEC=number
- The program requests to extend the timeout by number microseconds.
This will reset the current timeout to the specified value.
- ERRNO=number
- 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-time.
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 used.
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.
- --remove-pidfile
- 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.
- 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 returned:
- 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.
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 /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 /run/food.pid --retry 5
Demonstration of a custom schedule for stopping food:
start-stop-daemon --stop --oknodo --user food --name food \
--pidfile /run/food.pid --retry=TERM/30/KILL/5