init-d-script(5)

NAME#

init-d-script — interpreter for short and simple init.d scripts

DESCRIPTION#

Generic init.d script framework to reduce the redundant code in /etc/init.d/. The goal is to create an init.d script that is Debian and LSB compliant. When the Debian policy conflicts with the LSB, the Debian policy takes precedence.

This is a simple example on how init-d-script can be used to start and stop a daemon with PID file support:

#!/bin/sh /lib/init/init-d-script
### BEGIN INIT INFO
# Provides:          atd
# Required-Start:    $syslog $time $remote_fs
# Required-Stop:     $syslog $time $remote_fs
# Default-Start:     2 3 4 5
# Default-Stop:      0 1 6
# Short-Description: run at jobs
# Description:       Debian init script to start the daemon
#                    running at jobs.
### END INIT INFO
DAEMON=/usr/sbin/atd

The following variables affect behaviour of an init script:

DAEMON

Path to daemon being started. If the init script is not supposed to start any kind of daemon, it should be set to “none” and the functions do_start_override(), do_stop_override() and do_status_override() should be defined instead.

DAEMON_ARGS

Additional arguments, passed to daemon during start.

DESC

Full name or short description of the daemon, printed on screen. If unset, this variable defaults to the “NAME” value.

NAME

Additional environment variables are sourced from /etc/default/${NAME}. If unset, this variable defaults to the basename of the “DAEMON” value.

COMMAND_NAME

If this variable is set, it is used as argument to the --name option of start-stop-daemon(8). It may be useful if the value of the “NAME” variable is longer than the command name length supported by the running kernel. If the value is verbatim “none”, the command name will not be used to match the processes. If unset, this variable defaults to the “NAME” value.

PIDFILE

Path to file where the process identifier of the started daemon will be stored during start. If the value is verbatim “none”, the process identifier will not be stored in any file. If this variable is not set, it gets a sensible default value, so it is rarely necessary to set this variable explicitly.

SETPRIV_ARGS

If this directive is set and setpriv(1) is available, the invocation of start-stop-daemon(8) is wrapped in a call to setpriv(1) with the specified arguments. Note that the --chuid argument to start-stop-daemon(8) requires CAP_SETUID and CAP_SETGID in the bounding capabilities set.

RELOAD_SIGNAL

Signal number or name (without the SIG prefix) that will be sent to the process on reload. If the daemon performs reload action upon receiving a SIGHUP signal, this variable should be set to “1” or “HUP”.

The variables RELOAD_ARGS, START_ARGS and STOP_ARGS are additional arguments, passed to start-stop-daemon(8) during reload, start and stop actions, to override the default options.

Additionally, it is possible to change the behaviour of the resulting shell script by overriding some of the internal functions. To do so, define function with an _override suffix. So, for example, to override the do_status() function, one should define a do_status_override() function. The exception to this rule is the do_reload() function, whose override should be defined as-is, without the above-mentioned suffix.

Here is a control flow chart that explains what functions are called and when:

/etc/init.d/script start
  do_start
    do_start_prepare # no-op
    do_start_cmd     # start-stop-daemon is called here
    do_start_cleanup # no-op

/etc/init.d/script stop
  do_stop
    do_stop_prepare # no-op
    do_stop_cmd     # start-stop-daemon is called here
    do_stop_cleanup # no-op

/etc/init.d/script status
  do_status

/etc/init.d/script reload
  do_reload
    do_usage
    exit 3

/etc/init.d/script force-reload
  do_force_reload
    do_reload   # if overridden
    do_restart
      do_restart_prepare
      do_stop_cmd
      do_start_cmd
      do_restart_cleanup

/etc/init.d/script restart
  do_force_restart
/etc/init.d/script try-restart
  if do_status; then
    do_restart
      do_restart_prepare
      do_stop_cmd  # start-stop-daemon is called here
      do_start_cmd # start-stop-daemon is called here
      do_restart_cleanup

/etc/init.d/script <arg>
  do_unknown <arg>
    exit 3

/etc/init.d/script
  do_usage

As can be seen, by default, the script does not support the reload action; it should be implemented by the script writer by defining a do_reload() function.

If do_reload() is not defined but do_reload_cmd() is, the latter will be called on reload, after do_reload_prepare() and before do_reload_cleanup().

SEE ALSO#

inittab(8), service(8), setpriv(1), update-rc.d(8).

AUTHORS#

Petter Reinholdtsen ⟨[email protected]⟩