start-stop-daemon(8) dpkg suite start-stop-daemon(8)
NAME
start-stop-daemon - start and stop system daemon programs
SYNOPSIS
start-stop-daemon [option...] command
DESCRIPTION
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
-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
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 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.
EXIT STATUS
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.
EXAMPLE
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
1.21.22 2023-05-11 start-stop-daemon(8)
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