Difference between revisions of "util-vserver:InitStyles"

Latest revision as of 22:17, 21 October 2011

Guests can be started using one of the following init styles:

• plain
  • Launches a unique init process for the guest that appears to run as PID 1.
  • Guest's init process executes the rc scripts.
  • Therefore, you cannot watch the startup process.
  • However, any shutdown or restart command should work
• sysv (default)
  • Executes the runlevel scripts directly.
  • You can watch the startup process.
  • Slightly lighter weight since no additional init process is needed.
  • The vserver sees a fake init with PID 1 that has the same properties as the real init on the host.
  • You must use "reboot -f" or "halt -f" to restart or shut down from within the guest.
  • Default start runlevel is 3, and stop is 6
• gentoo
  • Like sysv but works on Gentoo-based guests.
  • Was deprecated but has been reinstated around util-vserver 0.30.212.
• minit
  • Like plain init but smaller.
  • minit must be installed on the guest.
  • http://www.fefe.de/minit/

[edit] Configuration

The init style should go in a file containing a single word: sysv, plain, etc.

 /etc/vservers/<NAME>/apps/init/style

If the file doesn't exist, sysv will be used. If the word isn't recognized, the guest will not be started and an error will be printed.

[edit] Using runit

runit is an init replacement that provides service monitoring. There currently are at least three ways to use it with vserver:

• Set initstyle to plain; this allows you to launch your own runit inside the vserver.
  • This is the most straightforward way. Guests can shut themselves down and restart as usual. Disadvantage: once extra runit-init process per guest.
• Use a persistent context for the guest, and just run the services inside it, not runit itself. This is discussed in Running runit-supervised services inside a vserver.
• Set initstyle to sysv, but cmd.start to "/etc/runit/2" and cmd.stop to "/etc/runit/3".
  • Advantage: you can run a vserver supervised by runit running on the host.

For this to work, you must customize /etc/runit/2 in the vserver as follows:

#!/bin/sh

trap ":" HUP INT QUIT ILL TRAP ABRT BUS FPE USR1 SEGV USR2 PIPE ALRM TERM CHLD CONT STOP TSTP TTIN TTOU URG XCPU XFSZ VTALRM PROF WINCH IO PWR SYS

PATH=/usr/local/bin:/usr/local/sbin:/bin:/sbin:/usr/bin:/usr/sbin:/usr/X11R6/bin

runsvchdir default >/dev/null

env - PATH=$PATH \
runsvdir -P /var/service 'log: ...........................................................................................................................................................................................................................................................................................................................................................................................................'

exec /etc/runit/3

Now, you can set up a runit service on the host with a run script like this one:

#!/bin/sh
exec 2>&1
exec vserver name-of-vserver start

This way:

• vserver start doesn't exit until runsvdir terminates.
• If runsvdir terminates, all services running inside the vserver are stopped.
• vserver stop works as expected.
  • Update: with util-vserver 0.30.212 on amd64, it doesn't. The signal never reaches runsvdir.
• You can control the vserver using sv like any other service, provided all processes running inside it are managed by runit.
  • If there are processes left inside after all the services exited, runit running on the host won't be able to restart the vserver until those stray processes are killed somehow.
  • You may want to add something to this effect to the finish script of the vserver service, but it may not be a good idea. Be sure you know what you are doing, as always.

Still, this may not be the best way to integrate runit with vserver. Running runit-supervised services inside a vserver may be better if you only run a specific service in a guest and it seems wasteful to keep extra processes around. Using the plain initstyle and starting runit-init in each guest is best if you want to make your guests behave like a physical system. It's also the most hassle-free approach.

--Guy- 02:30, 2 February 2007 (CET)