On 20/10/14 20:17, Lars Ellenberg wrote: > In other OSes, ps may be able to give a good enough equivalent?
Debian's start-stop-daemon executable might be worth considering here - it's used extensively in the init script infrastructure of Debian (and derivatives, over several different OS kernels), and so is well debugged, and in my experience beats re-implementing it's functionality. http://anonscm.debian.org/cgit/dpkg/dpkg.git/tree/utils/start-stop-daemon.c I've used it in pacemaker resource control scripts before successfully - it's kill expression support is very useful in particular on HA. Tim. 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 exe‐ cutable specified by --exec or, if specified, by --startas. Any arguments given after -- on the command line are passed unmodi‐ fied 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 termi‐ nated. -T, --status Check for the existence of a specified process, and returns an exit status code, according to the LSB Init Script Actions. -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. The pid must be a number greater than 0. --ppid ppid Check for a process with the specified ppid (parent pid). The ppid must be a number greater than 0. -p, --pidfile pid-file Check whether a process has created the file pid-file. Note: using this matching option alone might cause unintended pro‐ cesses to be acted on, if the old process terminated without being able to remove the pid-file. -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 exe‐ cutable will point to the interpreter. Take into account pro‐ cesses 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 pro‐ cesses 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 speci‐ fied, 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 mes‐ sages. -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' 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 start‐ ing 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. -C, --no-close Do not close any file descriptor when forcing the daemon into the background. Used for debugging purposes to see the process output, or to redirect file descriptors to log the process out‐ put. 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. The priority can be optionally spec‐ ified by appending a : followed by the value. The default prior‐ ity 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 cur‐ rently supported values for class are idle, best-effort and real-time. -k, --umask mask This sets the umask of the process before starting it. -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. 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 sched‐ ule 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 Debian Project 2014-03-26 start-stop-daemon(8) -- South East Open Source Solutions Limited Registered in England and Wales with company number 06134732. 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