Difference between revisions of "Runit"

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=== Using runit alongside systemd ===
 
=== Using runit alongside systemd ===
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==== Using BusyBox's implementation ====
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[[BusyBox]] provides a minimal implementation of runit that can be used for simple processing supervision needs. First, create symbolic links to the BusyBox binary for the necessary tools that are going to be needed:
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# busybox --list | awk '/runsv|chpst|svlog|^sv$/' | xargs -I{} ln -sv /usr/bin/busybox /usr/local/bin/{}
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Afterwards, a [[systemd]] unit file can be created in order to run BusyBox's runit when needed:
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{{hc|1=/etc/systemd/system/busybox-runit.service|2=[Unit]
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Description=Runit service supervision - BusyBox implementation
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Documentation=http://smarden.org/runit/ https://busybox.net/downloads/BusyBox.html
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[Service]
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Environment="PATH=/usr/local/sbin:/usr/local/bin:/usr/bin"
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ExecStart=/usr/local/bin/runsvdir -P /var/service
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KillSignal=SIGHUP
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KillMode=process
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Restart=always
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SuccessExitStatus=111
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[Install]
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WantedBy=multi-user.target}}
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{{Note|
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* This example unit file presupposes that the directory which is going to contain the enabled services is {{ic|/var/service}}. This path can be changed according to each specific use case.
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* The {{ic|SIGHUP}} kill signal is used instead of the default {{ic|SIGTERM}}, and only on the main ''runsvdir'' process (thanks to {{ic|1=KillMode=process}}) so that processes being controlled by BusyBox's runit implementation are controllably stopped by ''runsvdir'' before terminating the supervisor. When ''runsvdir'' ends the processes that are being supervised after receiving a {{ic|SIGHUP}} signal, it exits with an status code of 111, which needs to be interpreted as a success.}}
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Be sure to create the directory which is going to be supervised by ''runsvdir'' according to the systemd unit file created. It is also recommended to create a directory in which runit services can be stored (usually {{ic|/etc/sv}}), and only enabled when needed by creating a symbolic link directed to them from the directory being supervised.
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When everything is correctly configured, {{ic|busybox-runit.service}} can be [[systemd#Using units|enabled and started]].
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==== Using standard runit ====
  
 
It is possible to use runit as a simple process supervisor alongside the default Arch Linux's init system ([[systemd]]). For this purpose, install {{aur|runit-systemd}}, which provides a barebones runit installation without any stage scripts ({{ic|<nowiki>/etc/runit/{1..3}</nowiki>}}) or runlevels ({{ic|/etc/runit/runsvdir/*}}), which are generally only useful when using runit as the init system. The package provides a directory ({{ic|/var/service}}) in which the desired runit services can be put and a systemd unit which starts runit monitoring that directory. Only the services configured in {{ic|/var/service}} will be supervised by runit. Just [[systemd#Using units|enable and start]] {{ic|runit.service}}.
 
It is possible to use runit as a simple process supervisor alongside the default Arch Linux's init system ([[systemd]]). For this purpose, install {{aur|runit-systemd}}, which provides a barebones runit installation without any stage scripts ({{ic|<nowiki>/etc/runit/{1..3}</nowiki>}}) or runlevels ({{ic|/etc/runit/runsvdir/*}}), which are generally only useful when using runit as the init system. The package provides a directory ({{ic|/var/service}}) in which the desired runit services can be put and a systemd unit which starts runit monitoring that directory. Only the services configured in {{ic|/var/service}} will be supervised by runit. Just [[systemd#Using units|enable and start]] {{ic|runit.service}}.

Revision as of 15:12, 30 December 2017

Tango-view-refresh-red.pngThis article or section is out of date.Tango-view-refresh-red.png

Reason: Busybox also has a runit implementation, replace instructions in the article to use this instead of constant-in-flux user packages (Discuss in Talk:Runit#)

Runit is a process supervisor. It includes runit-init, which can replace sysv's init as pid1, or can be run from inittab or your init system of choice. Runit's simple collection of tools can be used to build flexible dependency structures and distributed systems, or blazing fast parallel runlevel changes (including the initial boot).

See G. Pape's Runit Page for a complete description, but follow the installation instructions below for your Arch system.

Installation

Using runit alongside systemd

Using BusyBox's implementation

BusyBox provides a minimal implementation of runit that can be used for simple processing supervision needs. First, create symbolic links to the BusyBox binary for the necessary tools that are going to be needed:

# busybox --list | awk '/runsv|chpst|svlog|^sv$/' | xargs -I{} ln -sv /usr/bin/busybox /usr/local/bin/{}

Afterwards, a systemd unit file can be created in order to run BusyBox's runit when needed:

/etc/systemd/system/busybox-runit.service
[Unit]
Description=Runit service supervision - BusyBox implementation
Documentation=http://smarden.org/runit/ https://busybox.net/downloads/BusyBox.html

[Service]
Environment="PATH=/usr/local/sbin:/usr/local/bin:/usr/bin"
ExecStart=/usr/local/bin/runsvdir -P /var/service
KillSignal=SIGHUP
KillMode=process
Restart=always
SuccessExitStatus=111

[Install]
WantedBy=multi-user.target
Note:
  • This example unit file presupposes that the directory which is going to contain the enabled services is /var/service. This path can be changed according to each specific use case.
  • The SIGHUP kill signal is used instead of the default SIGTERM, and only on the main runsvdir process (thanks to KillMode=process) so that processes being controlled by BusyBox's runit implementation are controllably stopped by runsvdir before terminating the supervisor. When runsvdir ends the processes that are being supervised after receiving a SIGHUP signal, it exits with an status code of 111, which needs to be interpreted as a success.

Be sure to create the directory which is going to be supervised by runsvdir according to the systemd unit file created. It is also recommended to create a directory in which runit services can be stored (usually /etc/sv), and only enabled when needed by creating a symbolic link directed to them from the directory being supervised.

When everything is correctly configured, busybox-runit.service can be enabled and started.

Using standard runit

It is possible to use runit as a simple process supervisor alongside the default Arch Linux's init system (systemd). For this purpose, install runit-systemdAUR, which provides a barebones runit installation without any stage scripts (/etc/runit/{1..3}) or runlevels (/etc/runit/runsvdir/*), which are generally only useful when using runit as the init system. The package provides a directory (/var/service) in which the desired runit services can be put and a systemd unit which starts runit monitoring that directory. Only the services configured in /var/service will be supervised by runit. Just enable and start runit.service.

The package arch-runit-servicesAUR provides some example services that can be used. This package puts the services in /etc/sv. The services inside can be symlinked to /var/service for them to be used.

Using runit

The Tools

  • sv - used for controlling services, getting status of services, and dependency checking.
  • chpst - control of a process environment, including memory caps, limits on cores, data segments, environments, user/group privileges, and more.
  • runsv - supervises a process, and optionally a log service for that process.
  • svlogd - a simple but powerful logger, includes auto-rotation based on different methods (time, size, etc), post-processing, pattern matching, and socket (remote logging) options. Say goodbye to logrotate and the need to stop your services to rotate logs.
  • runsvchdir - changes service levels (runlevels, see below).
  • runsvdir - starts a supervision tree
  • runit-init - PID 1, tiny, does almost nothing, dietlibc staticly compiled. Just what you want your PID 1 to be.

See the manpages for usage details not covered below.

The Extras

Added by runit-dietlibc and runit-run

  • /etc/runit/1 - bootstraps the system using arch rc scripts
  • /etc/runit/2 - starts single or multi-user runlevels using arch's rc.single or rc.multi
  • /etc/runit/3 - brings the system down using arch's rc scripts
  • /etc/runit/runsvdir/* - various runlevels
  • /usr/bin/rsvlog - a wrapper to svlogd meant to be symlinked as 'run' in a log service
  • /etc/sv/* - the service directories available (more available here when you install runit-services-git)

Added by runit-scripts

  • /etc/runit/1_new - meant to be an alternate way to bootstrap, does not necessarily use arch boot scripts
  • /etc/runit/2_new - single/multi user runlevels (not based on arch scripts)
  • /etc/runit/3_new - take the system down
  • /etc/runit/runsvdir/all - every service directory available
  • /etc/runit/runsvdir/* - various runlevels
  • /usr/bin/nsvlog - wrapper meant to be symlinked as 'run' in a log service

Run Levels and Service Directories

Runit uses directories of symlinks to specify runlevels, other than the 3 main ones, which are defined in /etc/runit/1, 2, and 3.

1 bootstraps the system, 2 starts runsvdir on /service, and 3 stops the system.

While in run level 2, you are not constrained to any amount of service levels (equivalent to runlevels in sysvinit). You can runschdir to any directory (full of service directory symlinks) you've made in /etc/runit/runsvdir/. This becomes very handy in cases where you have an HA (Failover) setup, and you have one machine that can take over services for many other machines, simply by runsvchdir <theservicedir>.

You can also run trees of dependent service levels by having user-level supervision directories. See User Level Services below.

By default, the runit-run package uses a very minimal service set, defined in /etc/runit/runsvdir/archlinux-default and symlinked to /etc/runit/runsvdir/default.

It only gives gettys on tty2 and tty3, so you will boot to just console scroll and a tidy 'runsvchdir: default: current'. This means when you start X it will be on tty4.

To go back to the standard arch consoles, remove the link /service/ngetty and link as many /etc/sv/*getty* services you like in /service, or edit the /etc/sv/ngetty/run file to get more getties. Better yet, create your own directory in /etc/runit/runsvdir and add the symlinks you want for just the services you desire. Remember to take any services you start with runit out of DAEMONS in /etc/rc.conf or systemctl disable them, they do not need to be started there, and runit will allow parallel startup without backgrounding them.

General Use

Tango-view-refresh-red.pngThis article or section is out of date.Tango-view-refresh-red.png

Reason: Every runit package in the AUR uses /var/service and not /service. (Discuss in Talk:Runit#)

For convenience I'll be using /service as the service directory in these examples. Since this has not been accepted by FHS, it is only made available as a symlink in the runit-run package. This allows importing of /service scripts written by others without as much fuss. If you only install runit-musl, you would use /var/service as your service directory, or make the /service symlink to /var/service yourself.

Listing running services

# sv s /service/*
   run: /service/agetty-2: (pid 4120) 7998s
   run: /service/agetty-3: (pid 4119) 7998s
   run: /service/bougyman: (pid 4465) 7972s
   run: /service/bougyx: (pid 4135) 7998s; run: log: (pid 4127) 7998s
   run: /service/cron: (pid 4137) 7998s; run: log: (pid 4122) 7998s
   run: /service/dialer: (pid 4121) 7998s
   run: /service/qmail: (pid 4138) 7998s; run: log: (pid 4126) 7998s
   run: /service/smtpd: (pid 4136) 7998s; run: log: (pid 4125) 7998s
   run: /service/socklog-klog: (pid 4139) 7998s; run: log: (pid 4132) 7998s
   run: /service/socklog-unix: (pid 4133) 7998s; run: log: (pid 4124) 7998s
   run: /service/ssh: (pid 4134) 7998s; run: log: (pid 4123) 7998s

Services should live in /etc/sv; however, the runit-scripts package puts a bunch of common ones in /etc/runit/runsvdir/all. We're working to replace/convert these to /etc/sv in the runit-services-git package.

Create and Start a service:

# ln -s /etc/sv/ssh /service/ssh

Stops a service immediately (would still start on next boot):

# sv d ssh

Restarts a service:

# sv t ssh

Reloads a service:

# sv h ssh

Shows status of a service and it's log service:

# sv s ssh

Stops a service, and disables it (won't start next boot):

# rm /service/ssh

Refer to man sv for more details.

Shut down the system

# runit-init 0

Reboot the system

# runit-init 6

User Level Services

Tango-inaccurate.pngThe factual accuracy of this article or section is disputed.Tango-inaccurate.png

Reason: It is recommended to use the integrated chpst for this purpose, rather than using sudo. See the Runit FAQ. (Discuss in Talk:Runit#)

You can extend the supervision tree by starting a runsvdir as a specific user, giving that user control of their own supervise tree.

Add a user level service tree

# mkdir -p /etc/sv/homes/joeuser

Create /etc/sv/homes/joeuser/run with the following:

   #!/bin/sh
   export PATH=/home/joeuser/bin:$PATH # optional, if your services rely on binaries in ~/bin
   exec 2>&1 \
     sudo -H -u joeuser runsvdir -P /home/joeuser/service 'log:...................................................................................................................................' # Requires sudo, of course
     
# chmod 700 /etc/sv/homes/joeuser/run

Then symlink /etc/sv/homes/joeuser to /service and any service joe puts in ~/service will start, as him, with his environment.

(the .......... represent placeholders, the proceess will print stdout/err every 5 seconds for each placeholder . you use in this case)

Create an X session service for a user

# mkdir -p /etc/sv/joeuserX

Create the /etc/sv/joeuserX/run script with the following

   #!/bin/sh
   exec 2>&1 \
     su -c xinit - joeuser
# chmod 700 /etc/sv/joeuserX/run

Then symlink /etc/sv/joeuserX to /service. joe's X session will now always run (in this runlevel). To protect it using joe's ssh passphrase, use the following in your .xinitrc:

   #!/bin/sh
   ...
   SNIP
   ...
   xscreensaver&
   eval $(keychain --eval)
   exec sh -c \
     'SSH_ASKPASS=/usr/lib/openssh/ssh-askpass-fullscreen ssh-add < /dev/null \
      && exec stumpwm'

Replace the 'stumpwm' with the command to launch your window manager or desktop environment.

Requires the 'keychain' and 'ssh-askpass-fullscreen' packages, or you could replace 'eval $(keychain)' with 'eval $(ssh-agent) and replace ssh-askpass-fullscreen with any ssh passphrase asker. The fullscreen version guarantees protection of your desktop, so we prefer that. This also exports your key to all your x apps, so you do not need another keychain manager for ssh. In addition, 'keychain' (as opposed to just ssh-agent) supports gpg passphrase caching, as well, not just the ssh keys.

Advanced Recipes

Running a read-only Postgresql Slave database in-memory

This recipe was created for a small but vital database which required very high read throughput. To sort it out we use Postgresql's Streaming Replication and Hot Standby mode.

Requirements

  • Postgresql 9.0 or above
  • runit-services (includes /etc/sv/postgresql)
  • Rsync (for initial replication)

Instructions

1. Create /etc/sv/pg_mem/log directory

# mkdir -p /etc/sv/pg_mem/log

2. Create three new files

/etc/sv/pg_shm/run:

   #!/bin/sh -e
   sleep 3 # Give postgresql a chance to start and replay any transactions
   
   . /etc/conf.d/pg_shm # Read any conf vars
   PG_DISK_ROOT=/var/lib/postgres # Where the 'master' data directory lives
   
   [ -d "$PGROOT" ] || mkdir -p "$PGROOT" # Create the new $PGROOT if it does not exist
   
   sv -w7 c postgresql 2>&1
   
   # Stop the main postgres from making changes by enttering backup mode
   psql -U postgres -c "SELECT pg_start_backup('seed',true)" 2>&1
   # Sync the main postgres data dir to our new $PGROOT
   rsync --progress --delete -a "$PG_DISK_ROOT/data" "$PGROOT/" --exclude=postmaster.pid 2>&1
   # Allow changes on the primary server again
   psql -U postgres -c "SELECT pg_stop_backup()" 2>&1
   
   # Set up the hot standby mode on the slave server
   echo "hot_standby = 'on'" >> "$PGROOT/data/postgresql.conf"
   echo "port = $PGPORT" >> "$PGROOT/data/postgresql.conf"
   echo "standby_mode = 'on'" >> "$PGROOT/data/recovery.conf"
   echo "primary_conninfo = 'host=localhost port=5432 user=postgres'" >> "$PGROOT/data/recovery.conf"
   echo "trigger_file = '/tmp/stop_replication'" >> "$PGROOT/data/recovery.conf"
   echo "restore_command = 'cp /var/lib/postgres/archive/%f \"%p\"'" >> "$PGROOT/data/recovery.conf"
   
   exec chpst -u postgres /usr/bin/postgres -D "$PGROOT/data" -c config_file="$PGROOT/data/postgresql.conf" 2>&1

Which requires /etc/conf.d/pg_shm:

PGROOT=/dev/shm/pg_mem
PGPORT=5434
PGLOG="/var/log/pg_mem.log"

as well as a file in /etc/sv/postgresql (or wherever your postgresql service directory lives) named 'finish':

#/bin/sh
sv -v i pg_shm

3. Make run and finish executable

# chmod 700 /etc/sv/pg_mem/run
# chmod 700 /etc/sv/postgresql/finish

4. Create a log service

# ln -s /usr/bin/rsvlog /etc/sv/pg_shm/log/run

5. Edit /var/lib/postgres/data/postmaster.conf, to enable wal archiving. See this The PostgreSQL page, steps 3 and 4, for detailed instructions on this.

6. Restart postgresql

# sv i postgresql

7. Start pg_shm (replace /service with your service directory, if it differs)

# ln -s /etc/sv/pg_shm /service

8. Make sure everything is running

# sv s postgresql pg_mem

That's it, you'll have a replica of your postgresql on-disk database published on port 5434, in read-only mode from the memory space utilized from /dev/shm.