G. Pape

# runit - a UNIX init scheme with service supervision

How to install runit
Upgrading from previous versions of runit

Benefits
How to replace init
How to use runit with current init
How to use dietlibc
Frequently asked questions

Runlevels
Service dependencies
A collection of run scripts

The `runit` program
The `runit-init` program
The `sv` program
The `runsvdir` program
The `runsvchdir` program
The `runsv` program
The `svlogd` program
The `chpst` program
The `utmpset` program

runit is a cross-platform Unix init scheme with service supervision, a replacement for sysvinit, and other init schemes. It runs on GNU/Linux, *BSD, MacOSX, Solaris, and can easily be adapted to other Unix operating systems. If runit runs for you on any other operating system, please let me know.

runit is discussed on the <supervision@list.skarnet.org> mailing list. Please contact this list and not me privately.

To subscribe send an empty email to <supervision-subscribe@list.skarnet.org>.

Mailing list archives are available at skarnet.org, and gmane.org.

The program runit is intended to run as Unix process no 1, it is automatically started by the runit-init `/sbin/init`-replacement if this is started by the kernel.

runit performs the system's booting, running and shutting down in three stages:

- Stage 1:
  runit starts `/etc/runit/1` and waits for it to terminate. The system's one time initialization tasks are done here. `/etc/runit/1` has full control over `/dev/console` to be able to start an emergency shell in case the one time initialization tasks fail.
- Stage 2:
  runit starts `/etc/runit/2` which should not return until the system is going to halt or reboot; if it crashes, it will be restarted. Normally, `/etc/runit/2` runs runsvdir. In Stage 2 runit optionally handles the INT signal (ctrl-alt-del keyboard request on Linux/i386).
- Stage 3:
  If runit is told to halt or reboot the system, or Stage 2 returns without errors, it terminates Stage 2 if it is running, and runs `/etc/runit/3`. The systems tasks to shutdown and halt or reboot are done here.

These are working examples for Debian sarge: /etc/runit/1, /etc/runit/2, /etc/runit/3.

The program runit-init is intended to replace `/sbin/init`. The command `init 0` tells runit to halt the system, and `init 6` to reboot. Runlevels are handled through the runsvdir and runsvchdir programs. Service dependencies are resolved automatically.

runit is optimized for reliability and small size. The amount of code in process no 1 should be minimal.

See How to install runit for installing runit, and How to replace init for configuring runit to run as process no 1. See How to use with current init if you want to use runit without replacing the current init scheme. Please read the list of Frequently asked questions with answers.

If runit on Linux is compiled and linked with the dietlibc, it yields in a statically linked `runit` binary of 8.5k size and this `ps axuw` output on my system:

     USER       PID %CPU %MEM   VSZ  RSS TTY      STAT START   TIME COMMAND
     root         1  0.0  0.0    20   16 ?        S     2002   0:02 runit

I recommend doing this; for instructions, see How to use dietlibc.

The following distributions are known to include or package runit:

- Debian GNU/Linux (as alternative init scheme)
- FreeBSD
- OpenBSD
- NetBSD
- Annvix (as default init scheme)
- Ubuntu (as alternative init scheme)
- Gentoo
- SME server
- OpenSDE
- T2
- Zinux Linux (as default init scheme)
- GoboLinux

If you know of more distributions, please let me know.

runit in use: I replaced sysvinit successfully with runit on several server systems and a laptop running Debian/GNU Linux sarge, woody, and potato. Here is an example:

     # strings /proc/1/exe |grep Id
     $Id: runit.c,v 1.7 2002/02/13 09:59:52 pape Exp $
     # uptime
      11:59:13 up 365 days, 23:22,  3 users,  load average: 0.01, 0.02, 0.00
     # ps axuw |head -n20
     USER       PID %CPU %MEM   VSZ  RSS TTY      STAT START   TIME COMMAND
     root         1  0.0  0.0    20   16 ?        S     2002   0:07 runit
     root         2  0.0  0.0     0    0 ?        SW    2002   0:00 [keventd]
     root         3  0.0  0.0     0    0 ?        SWN   2002   0:51 [ksoftirqd_CPU0]
     root         4  0.0  0.0     0    0 ?        SW    2002 144:38 [kswapd]
     root         5  0.0  0.0     0    0 ?        SW    2002   0:08 [bdflush]
     root         6  0.0  0.0     0    0 ?        SW    2002   7:24 [kupdated]
     root       168  0.0  0.0  1652  168 ?        S     2002   0:27 /usr/sbin/cron
     root       174  0.0  0.0    36   24 ?        S     2002   1:06 runsvdir /var/service log: ...............................................................................................
     root       176  0.0  0.0    20   20 ?        S     2002   0:00 runsv qmail-send
     root       177  0.0  0.0    20   20 ?        S     2002   0:00 runsv getty-5
     root       178  0.0  0.0    20   20 ?        S     2002   0:00 runsv getty-4
     root       179  0.0  0.0    20   20 ?        S     2002   0:00 runsv getty-3
     root       180  0.0  0.0    20   20 ?        S     2002   0:00 runsv getty-2
     root       182  0.0  0.0    20   20 ?        S     2002   0:00 runsv socklog-unix
     root       183  0.0  0.0  1256    4 tty5     S     2002   0:00 /sbin/getty 38400 tty5 linux
     root       184  0.0  0.0  1256    4 tty3     S     2002   0:00 getty 38400 tty3 linux
     root       185  0.0  0.0    20   20 ?        S     2002   0:00 runsv socklog-klog
     root       186  0.0  0.0    20   20 ?        S     2002   0:00 runsv ssh
     root       187  0.0  0.0  1256    4 tty4     S     2002   0:00 getty 38400 tty4 linux
     # pstree
     runit-+-bdflush
           |-cron
           |-gcache
           |-keventd
           |-ksoftirqd_CPU0
           |-kswapd
           |-kupdated
           `-runsvdir-+-runsv-+-multilog
                      |       `-qmail-send-+-qmail-clean
                      |                    |-qmail-lspawn
                      |                    `-qmail-rspawn---qmail-remote
                      |-4*[runsv---getty]
                      |-2*[runsv-+-multilog]
                      |          `-socklog]
                      |-runsv-+-multilog
                      |       `-sshd-+-sshd---sshd---bash---bash---pstree
                      |              `-sshd---sshd---rsync
                      |-runsv---clockspeed
                      |-runsv-+-dnscache
                      |       `-multilog
                      |-runsv---apache-ssl-+-9*[apache-ssl]
                      |                    |-gcache
                      |                    `-4*[multilog]
                      |-7*[runsv-+-multilog]
                      |          `-tcpserver]
                      |-4*[runsv-+-multilog]
                      |          `-tinydns]
                      |-runsv---uncat
                      |-2*[runsv-+-multilog]
                      |          `-tcpsvd]
                      |-runsv-+-svlogd
                      |       `-tcpsvd-+-smtpfront-qmail
                      |                `-smtpfront-qmail---qmail-queue
                      `-runsv-+-svlogd
                              `-tcpsvd---bincimap-up---bincimapd

See http://smarden.org/runit/ for recent informations.

Related links:

- minit - a small yet feature-complete init
- svscan as process 1 - by Paul Jarc
- sysvinit - source code
- FreeBSD's init - CVS repository
- NetBSD's init - CVS repository
- OpenBSD's init - CVS repository
- Linux Boot Scripts - by Richard Gooch