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/repos/baseimage-docker.git
synced 2025-12-30 08:01:31 +01:00
Improve the init system: support skipping startup files and running a custom main command
This commit is contained in:
Hongli Lai (Phusion)
parent
d884118827
commit
b6dac86e04
@ -1,6 +1,9 @@
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## 0.9.6
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* Fixed a bug in `my_init`: child processes that have been adopted during execution of init scripts are now properly reaped.
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* Much improved `my_init`:
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* It is now possible to run and watch a custom command, possibly in addition to running runit. See "Running a one-shot command in the container" in the README.
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* It is now possible to skip running startup files such as /etc/rc.local.
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## 0.9.5 (release date: 2014-02-06)
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45
README.md
45
README.md
@ -40,6 +40,7 @@ You can configure the stock `ubuntu` image yourself from your Dockerfile, so why
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* [Getting started](#getting_started)
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* [Adding additional daemons](#adding_additional_daemons)
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* [Running scripts during container startup](#running_startup_scripts)
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* [Running a one-shot command in the container](#oneshot)
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* [Login to the container via SSH](#login)
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* [Building the image yourself](#building)
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* [Conclusion](#conclusion)
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@ -154,6 +155,50 @@ The following example shows how you can add a startup script. This script simply
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RUN mkdir -p /etc/my_init.d
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ADD logtime.sh /etc/my_init.d/logtime.sh
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<a name="oneshot"></a>
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### Running a one-shot command in the container
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Normally, when you want to run a single command in a container, and exit immediately after the command, you invoke Docker like this:
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docker run YOUR_IMAGE COMMAND ARGUMENTS...
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However the downside of this approach is that the init system is not started. That is, while invoking `COMMAND`, important daemons such as cron and syslog are not running. Also, orphaned child processes are not properly reaped, because `COMMAND` is PID 1.
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Baseimage-docker provides a facility to run a single one-shot command, while solving all of the aforementioned problems. Run a single command in the following manner:
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docker run YOUR_IMAGE /sbin/my_init -- COMMAND ARGUMENTS ...
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This will perform the following:
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* Runs all system startup files, such as /etc/my_init.d/* and /etc/rc.local.
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* Starts all runit services.
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* Runs the specified command.
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* When the specified command exits, stops all runit services.
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For example:
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$ docker run phusion/baseimage:<VERSION> /sbin/my_init -- ls
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*** Running /etc/my_init.d/00_regen_ssh_host_keys.sh...
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No SSH host key available. Generating one...
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Creating SSH2 RSA key; this may take some time ...
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Creating SSH2 DSA key; this may take some time ...
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Creating SSH2 ECDSA key; this may take some time ...
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*** Running /etc/rc.local...
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*** Booting runit daemon...
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*** Runit started as PID 80
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*** Running ls...
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bin boot dev etc home image lib lib64 media mnt opt proc root run sbin selinux srv sys tmp usr var
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*** ls exited with exit code 0.
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*** Shutting down runit daemon (PID 80)...
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*** Killing all processes...
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You may find that the default invocation is too noisy. Or perhaps you don't want to run the startup files. You can customize all this by passing arguments to `my_init`. Invoke `docker run YOUR_IMAGE /sbin/my_init --help` for more information.
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The following example runs `ls` without running the startup files and with less messages, while running all runit services:
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$ docker run phusion/baseimage:<VERSION> /sbin/my_init --skip-startup-files --quiet -- ls
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bin boot dev etc home image lib lib64 media mnt opt proc root run sbin selinux srv sys tmp usr var
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<a name="login"></a>
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### Login to the container via SSH
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279
image/my_init
279
image/my_init
@ -1,8 +1,42 @@
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#!/usr/bin/python2
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import os, sys, stat, signal, errno
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import os, sys, stat, signal, errno, argparse, time
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pid = None
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status = None
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KILL_PROCESS_TIMEOUT = 5
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KILL_ALL_PROCESSES_TIMEOUT = 5
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LOG_LEVEL_ERROR = 1
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LOG_LEVEL_WARN = 1
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LOG_LEVEL_INFO = 2
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LOG_LEVEL_DEBUG = 3
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log_level = None
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class AlarmException(Exception):
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pass
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def error(message):
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if log_level >= LOG_LEVEL_ERROR:
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sys.stderr.write("*** %s\n" % message)
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def warn(message):
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if log_level >= LOG_LEVEL_WARN:
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print("*** %s" % message)
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def info(message):
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if log_level >= LOG_LEVEL_INFO:
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print("*** %s" % message)
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def debug(message):
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if log_level >= LOG_LEVEL_DEBUG:
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print("*** %s" % message)
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def ignore_signals_and_raise_keyboard_interrupt(signame):
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signal.signal(signal.SIGTERM, signal.SIG_IGN)
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signal.signal(signal.SIGINT, signal.SIG_IGN)
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raise KeyboardInterrupt(signame)
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def raise_alarm_exception():
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raise AlarmException('Alarm')
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def listdir(path):
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try:
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@ -20,100 +54,185 @@ def is_exe(path):
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except OSError:
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return False
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def reap_child(signum, frame):
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global pid, status, waiting_for_runit
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try:
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result = os.wait3(os.WNOHANG)
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if result is not None and pid == result[0]:
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status = result[1]
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except OSError:
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pass
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def waitpid_reap_other_children(pid):
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done = False
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status = None
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while not done:
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this_pid, status = os.waitpid(-1, 0)
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done = this_pid == pid
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return status
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def stop_child_process(name, pid):
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print("*** Shutting down %s (PID %d)..." % (name, pid))
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def stop_child_process(name, pid, signo = signal.SIGTERM, time_limit = KILL_PROCESS_TIMEOUT):
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info("Shutting down %s (PID %d)..." % (name, pid))
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try:
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os.kill(pid, signal.SIGHUP)
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os.kill(pid, signo)
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except OSError:
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pass
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signal.alarm(time_limit)
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try:
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try:
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waitpid_reap_other_children(pid)
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except OSError:
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pass
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except AlarmException:
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warn("%s (PID %d) did not shut down in time. Forcing it to exit.")
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try:
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os.kill(pid, signal.SIGKILL)
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except OSError:
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pass
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try:
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waitpid_reap_other_children(pid)
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except OSError:
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pass
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finally:
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signal.alarm(0)
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def run_command_killable(*argv):
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global pid
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filename = argv[0]
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status = None
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pid = os.spawnvp(os.P_NOWAIT, filename, argv)
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signal.signal(signal.SIGINT, lambda signum, frame: stop_child_process(filename, pid))
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signal.signal(signal.SIGTERM, lambda signum, frame: stop_child_process(filename, pid))
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try:
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status = waitpid_reap_other_children(pid)
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except BaseException as s:
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warn("An error occurred. Aborting.")
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stop_child_process(filename, pid)
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raise
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if status != 0:
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error("%s failed with exit code %d\n" % (filename, status))
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sys.exit(1)
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def kill_all_processes(time_limit):
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info("Killing all processes...")
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try:
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os.kill(-1, signal.SIGTERM)
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except OSError:
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pass
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signal.alarm(time_limit)
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try:
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# Wait until no more child processes exist.
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done = False
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while not done:
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try:
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this_pid, status = os.waitpid(-1, 0)
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done = this_pid == pid
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os.waitpid(-1, 0)
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except OSError as e:
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if e.errno == errno.EINTR:
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sys.exit(2)
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if e.errno == errno.ECHILD:
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done = True
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else:
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raise
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finally:
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signal.signal(signal.SIGINT, signal.SIG_DFL)
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signal.signal(signal.SIGTERM, signal.SIG_DFL)
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if status != 0:
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sys.stderr.write("*** %s failed with exit code %d\n" % (filename, status))
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sys.exit(1)
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# Run /etc/my_init.d/*
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for name in listdir("/etc/my_init.d"):
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filename = "/etc/my_init.d/" + name
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if is_exe(filename):
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print("*** Running %s..." % filename)
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run_command_killable(filename)
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# Run /etc/rc.local.
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if is_exe("/etc/rc.local"):
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print("*** Running /etc/rc.local...")
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run_command_killable("/etc/rc.local")
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# Start runit.
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signal.signal(signal.SIGCHLD, reap_child)
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print("*** Booting runit...")
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pid = os.spawnl(os.P_NOWAIT, "/usr/bin/runsvdir", "/usr/bin/runsvdir", "-P", "/etc/service", "log: %s" % ('.' * 395))
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print("*** Runit started as PID %d" % pid)
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signal.signal(signal.SIGTERM, lambda signum, frame: stop_child_process("runit", pid))
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# Wait for runit, and while waiting, reap any adopted orphans.
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done = False
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while not done:
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try:
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this_pid, status = os.waitpid(pid, 0)
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done = True
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except OSError as e:
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if e.errno == errno.EINTR:
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# Try again
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except AlarmException:
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warn("Not all processes have exited in time. Forcing them to exit.")
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try:
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os.kill(-1, signal.SIGKILL)
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except OSError:
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pass
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finally:
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signal.alarm(0)
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def run_startup_files():
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# Run /etc/my_init.d/*
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for name in listdir("/etc/my_init.d"):
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filename = "/etc/my_init.d/" + name
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if is_exe(filename):
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info("Running %s..." % filename)
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run_command_killable(filename)
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# Run /etc/rc.local.
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if is_exe("/etc/rc.local"):
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info("Running /etc/rc.local...")
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run_command_killable("/etc/rc.local")
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def start_runit():
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info("Booting runit daemon...")
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pid = os.spawnl(os.P_NOWAIT, "/usr/bin/runsvdir", "/usr/bin/runsvdir",
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"-P", "/etc/service", "log: %s" % ('.' * 395))
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info("Runit started as PID %d" % pid)
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return pid
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def wait_for_runit_or_interrupt(pid):
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try:
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status = waitpid_reap_other_children(pid)
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return (True, status)
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except KeyboardInterrupt:
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return (False, None)
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def shutdown_runit_services():
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debug("Begin shutting down runit services...")
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os.system("/usr/bin/sv down /etc/service/*")
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def wait_for_runit_services():
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debug("Waiting for runit services to exit...")
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done = False
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while not done:
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done = os.system("/usr/bin/sv status /etc/service/* | grep -q '^run:'") != 0
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if not done:
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time.sleep(0.1)
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def main(args):
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if not args.skip_startup_files:
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run_startup_files()
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runit_exited = False
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exit_code = None
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if not args.skip_runit:
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runit_pid = start_runit()
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try:
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if len(args.main_command) == 0:
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runit_exited, exit_code = wait_for_runit_or_interrupt(runit_pid)
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if runit_exited:
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info("Runit exited with code %d" % exit_code)
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else:
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# The SIGCHLD handler probably caught it.
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done = True
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info("Running %s..." % " ".join(args.main_command))
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pid = os.spawnvp(os.P_NOWAIT, args.main_command[0], args.main_command)
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try:
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exit_code = waitpid_reap_other_children(pid)
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info("%s exited with exit code %d." % (args.main_command[0], exit_code))
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except KeyboardInterrupt:
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stop_child_process(args.main_command[0], pid)
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except BaseException as s:
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warn("An error occurred. Aborting.")
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stop_child_process(args.main_command[0], pid)
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raise
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sys.exit(exit_code)
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finally:
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if not args.skip_runit:
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shutdown_runit_services()
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if not runit_exited:
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stop_child_process("runit daemon", runit_pid)
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wait_for_runit_services()
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# Runit has exited. Reset signal handlers.
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print("*** Runit exited with code %s. Waiting for all services to shut down..." % status)
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signal.signal(signal.SIGCHLD, signal.SIG_DFL)
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signal.signal(signal.SIGTERM, signal.SIG_DFL)
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signal.siginterrupt(signal.SIGCHLD, False)
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signal.siginterrupt(signal.SIGTERM, False)
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# Parse options.
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parser = argparse.ArgumentParser(description = 'Initialize the system.')
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parser.add_argument('main_command', metavar = 'MAIN_COMMAND', type = str, nargs = '*',
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help = 'The main command to run. (default: runit)')
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parser.add_argument('--skip-startup-files', dest = 'skip_startup_files',
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action = 'store_const', const = True, default = False,
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help = 'Skip running /etc/my_init.d/* and /etc/rc.local')
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parser.add_argument('--skip-runit', dest = 'skip_runit',
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action = 'store_const', const = True, default = False,
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help = 'Do not run runit services')
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parser.add_argument('--no-kill-all-on-exit', dest = 'kill_all_on_exit',
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action = 'store_const', const = False, default = True,
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help = 'Don\'t kill all processes on the system upon exiting')
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parser.add_argument('--quiet', dest = 'log_level',
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action = 'store_const', const = LOG_LEVEL_WARN, default = LOG_LEVEL_INFO,
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help = 'Only print warnings and errors')
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args = parser.parse_args()
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log_level = args.log_level
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# Wait at most 5 seconds for services to shut down.
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import time
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def shutdown(signum = None, frame = None):
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global status
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if status is not None:
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sys.exit(status)
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signal.signal(signal.SIGALRM, shutdown)
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signal.alarm(5)
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done = False
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while not done:
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done = os.system("/usr/bin/sv status /etc/service/* | grep -q '^run:'") != 0
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if not done:
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time.sleep(0.5)
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shutdown()
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if args.skip_runit and len(args.main_command) == 0:
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error("When --skip-runit is given, you must also pass a main command.")
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sys.exit(1)
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# Run main function.
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signal.signal(signal.SIGTERM, lambda signum, frame: ignore_signals_and_raise_keyboard_interrupt('SIGTERM'))
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signal.signal(signal.SIGINT, lambda signum, frame: ignore_signals_and_raise_keyboard_interrupt('SIGINT'))
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signal.signal(signal.SIGALRM, lambda signum, frame: raise_alarm_exception())
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try:
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main(args)
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except KeyboardInterrupt:
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warn("Init system aborted.")
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exit(2)
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finally:
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if args.kill_all_on_exit:
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kill_all_processes(KILL_ALL_PROCESSES_TIMEOUT)
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