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runit-for-lfs General Usage Notes September 16, 2014
============================================================================
Runit is a mature and proven cross-platform init system for Unix/Linux that
provides for service daemon supervision, clean startup process state for
services, reliable logging, fast system boot up with parallel daemon
initialization, and small code size. Runit was originally developed by and is
still maintained by Gerrit Pape.
This runit-for-lfs project is an effort to tailor Runit specifically for Linux
From Scratch which has traditionally used SysVinit as its init system. Our
intention is to provide an alternative to users who are ready to move on from
SysVinit but want to avoid handing their systems over to Systemd.
How Runit Works
---------------
Runit works in three stages. Stage 1 runs when the kernel has finished its
system initialization tasks and hands off to the init system. Stage 1 involves
all one-time system initializations of a typical LFS system (e.g., mounting
filesystems, initializing the console, starting udev, setting the system
clock, etc.). When stage 1 returns, stage 2 is run and starts a supervision
service for all enabled daemons. Stage 2 monitors the service daemons and will
restart them if they should crash or stop for some reason. The sv executable
can be used to query the state of services and manually stop or restart them.
When stage 2 receives the signal to shutdown, stage 3 is run and handles the
task of shutting down the services and doing other tasks related to shutting
down the system.
kernel
|
1|
.--- /etc/runit/reboot ---. init 14
,---| 2 |<--- (runit-init) <---- init 0|6
| '--- /etc/runit/stopit ---' |
| 13 |
'------------------------------------> 3|
.-----> runit
| |
| |
.---<---------<----+-------->---------.
| | | |
4| | 6| 10|
runit/1 | runit/2 runit/3
| | | |
5| | 7| 11|
start things | runsvdir sv
| | | |
| | 8| |
'--->---'| runsv /var/service/*
| | |
| | 12|
| .../current/* stop things
| | |
| | |
| start things |
| monitor things |
| restart things |
| | |
| 9| |
'----<----'--------<---------'
1. kernel runs init which is a symlink to runit-init.
2. runit-init uses the owner excecute permission of reboot and stopit
to "signal" runit whether to reboot or halt at shutdown time.
3. runit-init runs runit.
4. runit runs stage 1.
5. stage 1 runs various boot time startup scripts or commands.
6. runit runs stage 2 when stage 1 returns.
7. stage 2 runs runsvdir which starts a runsv process for each service
in the current service directory.
8. runsv monitors each service and restarts them if they stop.
9. stage 2 does not return until time to shut down for reboot or halt.
10. runit runs stage 3 if told to shut down for reboot or halt, or if
stage 2 returns.
11. stage 3 runs sv to stop all services.
12. stage 3 also runs various shutdown commands or scripts and then
returns.
13. runit checks the owner execute permission of reboot and stopit to
determine whether to reboot or halt.
14. runit-init is called as init 0 or init 6 when the system is already
running and sets the owner execute permission of stopit and reboot
appropriately for runit to halt or reboot the system.
General Installation Notes
--------------------------
The runit-for-lfs project is meant to replace SysVinit with Runit which can be
installed instead of SysVinit in a new system or replace it in an existing
system. The general steps can be summarized this way...
1. Uninstall SysVinit and lfs-bootscripts
IMPORTANT NOTE: This step does just what it says and removes SysVinit
executables in /sbin such as init, halt, shutdown, runlevel, killall5, etc.,
and others such as ifup, ifdown, ipv4-static, ipv4-static-route, and rc. It
also removes the entire /etc/rc.d directory which includes all SysVinit
initscripts and usually the firewall rules file. It is a good idea to create
a backup of the system before installing this new init system.
2. Build and install Runit
3. Build and/or install several custom executables to replace ones removed
4. Install a minimal collection of service run scripts initially.
5. Install and enable the remaining service run scripts the system requires.
The included INSTALL file has detailed step-by-step instructions to accomplish
those installation tasks. At the end of those steps, the system will be
capable of booting with Runit handling system initialization chores and service
daemon startups. It then settles into its normal state of service supervision
until time to shut down.
Runlevels
---------
The runit-for-lfs project has two runlevels: single for administration and
multi for normal use. The default runlevel at boot time will always be multi. A
runlevel will have a corresponding directory in /etc/runit/runsvdir. Thus, the
two runlevels in our runit-for-lfs project have the following runlevel
directories:
/etc/runit/runsvdir/single
/etc/runit/runsvdir/multi
The run scripts for services and daemons are stored in /etc/sv. The two
runlevel directories will be populated with symlinks to services in /etc/sv.
When a runlevel is chosen as the current runlevel, all of the services and
daemons symlinked in that runlevel directory will be started and supervised.
Usually, the single runlevel which is for administrative use has only the
agetty symlinks, and the multi runlevel which is for normal use has symlinks
to all of the services that need to be running during normal use of the system.
At installation time, the single and multi runlevel directories will
contain symlinks only to basic agetty services for tty consoles. To enable
an additional service that has been installed in the system (e.g., sshd, dbus,
cups, etc.), change the terminal directory to the blfs-servicescript directory
in the runit-for-lfs package source tree and run the command as it is in the
BLFS book for installing the corresponding SysV initscript. For example, to
enable the fcron daemon after the fcron package has been installed...
tar xf runit-for-lfs-<version>
cd /runit-for-lfs/blfs-servicescripts
make install-fcron
The 'make install-fcron' command in that example will install the runit-for-lfs
run script for fcron, make it executable, and create a symlink for it in the
multi runlevel directory.
To create an additional runlevel, create a new runlevel directory in
/etc/runit/runsvdir and then in that new runlevel directory create symlinks to
the services in /etc/sv that should run in that new runlevel. For example,
mkdir /etc/runit/runsvdir/desktop
ln -sv /etc/sv/dbus /etc/runit/runsvdir/desktop
In that example, a new runlevel named "desktop" was created and a symlink to
/etc/sv/dbus was created in it which will result in the dbus daemon being
started and supervised any time the desktop runlevel is the current runlevel.
Continue creating symlinks in the new runlevel directory as needed.
So how does a runlevel such as single or multi become the current runlevel? A
symlink named /etc/runit/runsvdir/current is automatcially created pointing to
the current runlevel directory. It is this /etc/runit/runsvdir/current symlink
that is actually used by stage 2 to start services. So if
/etc/runit/runsvdir/current is a symlink to multi, then all the services in the
multi runlevel will be started and supervised. To change runlevels, use the
runsvchdir command which changes the symlink /etc/runit/runsvdir/current to
target the new runlevel specified in the runsvchdir command.
Examples and illustrations:
List enabled services for the "single" runlevel...
$ ls /etc/runit/runsvdir/single
List enabled services for the "multi" runlevel...
$ ls /etc/runit/runsvdir/multi
List enabled services for the "current" runlevel (could be single or multi)...
$ ls /etc/runit/runsvdir/current
List the available runlevels...
$ ls /etc/runit/runsvdir
Display the status of enabled services...
# sv status /etc/runit/runsvdir/current/*
Stop a service temporarily...
# sv stop /etc/runit/runsvdir/current/<service>
Disable a service in a runlevel permanently...
# rm -f /etc/runit/runsvdir/<runlevel>
Re-enable a service that had been disabled...
# ln -s /etc/sv/<service> /etc/runit/runsvdir/<runlevel>
Enabling Service Daemons
------------------------
The runit-for-lfs project includes a prepared and growing list of scripts to
start up many common services installed in typical LFS systems. They can be
found in the blfs-servicescript directory of the runit-for-lfs package source
tree. To enable a service that was already installed in the system when the
runit-for-lfs system was installed, merely untar the runit-for-lfs tarball,
change directories to the blfs-servicescript directory, and run the
corresponding 'make install-<service>' command as already described above.
When a package that includes a service daemon is installed after converting to
Runit for the init system, skip the usual step in the book to untar the
blfs-bootscript tarball and instead untar the runit-for-lfs tarball. Then
change to the blfs-servicescript directory and and run the corresponding 'make
install-<service>' command as already described above.
Our goal is to provide run scripts for all services included in the BLFS book.
However when a package that includes a service daemon is installed and no run
script directory exists for it in the runit-for-lfs source tree, then it is
usually a simple matter to create a run script for it in /etc/sv following some
of the existing run scripts as examples. Often a single command to start the
daemon is all that is needed. There also is an rc.local script provided by
runit-for-lfs for running commands at boot time. See the installed rc.local man
page for important details about using that.
Shutting Down and Rebooting
---------------------------
When runit-for-lfs is installed, the instructions in the INSTALL file remove
SysVinit and lfs-bootscripts. Some of the removed components have to do with
shutting down and rebooting. Runit is perfectly capable of doing those actions
on its own. However, during the installation of runit-for-lfs, some of those
uninstalled SysVinit components are replaced by special new versions of them
for compatibility purposes and for users who like using them.
halt
From Void Linux, this binary executable provides the functions of SysVinit's
halt program. See the halt man page.
shutdown
From Void Linux, this is a bash script that mimics the function of SysVinit's
shutdown program. See the shutdown man page.
poweroff
This is a symlink to halt to reproduce the action of the same symlink used by
SysVinit. See the halt man page.
reboot
This is a symlink to halt to reproduce the action of the same symlink used by
SysVinit. See the halt man page.
A Word About Pause
------------------
From Void Linux, the pause binary is an executable that is normally called from
scripts. It functions to stop the execution of the script until a TERM signal
is received. Some of the services in runit-for-lfs are not daemons in the
normal sense that they continue to run once they are started, but are instead
scripts that do a one-time action and exit. Some examples are iptables, alsa,
and network.
These kinds of service scripts create a problem for runsv which is the
component of Runit that monitors the services started by stage 2. When runsv
discovers that a monitored script has exited, it will run the service's finish
script and restart the run script. That's how service supervision works.
However, for service scripts like those mentioned above that normally exit,
runsv would start the script over and over. To prevent this situation for
service scripts of this type, a call to the pause binary is inserted at the end
of the script to keep it in a "running" state as far as runsv is concerned
until a TERM signal is received and then the scripts exits.
Things Done Differently Than Linux From Scratch
-----------------------------------------------
This runit-for-lfs project handles certain configuration tasks differently than
a typical LFS system does.
Setting the System and Hardware Clocks...
A Linux From Scratch system stores time information such as the time system
used by the hardware clock and other clock parameters in
/etc/sysconfig/clock and /etc/sysconfig/rc.site. This runit-for-lfs project
sets the hardware and system clocks using parameters set in /etc/runit.conf.
See man runit.conf for more about setting the system and hardware clocks.
Setting the Time Zone...
LFS configures the time zone at build time by copying the appropriate time
zone file from /usr/share/zoneinfo to /etc/localtime. This runit-for-lfs
project allows the user to set the time zone in /etc/runit.conf. At boot
time, the time zone set in /etc/runit.conf is used to update /etc/localtime
and set the kernel time zone. See man runit.conf for more about setting the
time zone in /etc/runit.conf.
Console Font...
LFS provides for setting console fonts, maps, and tables in
/etc/sysconfig/rc.site and /etc/sysconfig/console. This runit-for-lfs
project uses parameters set in /etc/runit.conf for that purpose. See man
runit.conf for more about setting console fonts in /etc/runit.conf.
Loading Additional Kernel Modules...
LFS allows the user to list modules for the kernel to load in
/etc/sysconfig/modules. This runit-for-lfs project uses parameters set in
/etc/runit.conf for that purpose. See man runit.conf for more about loading
kernel modules.
"Createfiles"...
LFS stores information about files and directories to be created at boot
time in /etc/sysconfig/createfiles. This runit-for-lfs project uses a
variable array in /etc/runit.conf for that purpose. See man runit.conf for
more about creating files and directories at boot time.
A special note about /etc/sysconfig/rc.site...
The functions of the LFS file /etc/sysconfig/rc.site mostly are not used by
this runit-for-lfs project or are handled in different locations and ways.
The /etc/sysconfig/rc.site file still will be sourced for the system
parameters LOGLEVEL, SYSKLOGD_PARMS, SKIPTMPCLEAN. Defaults will be used if
those are null or not set.
Summary of Runit's Important Files and Directories
--------------------------------------------------
Executables:
/sbin/runit-init
The first process started by the kernel via a symlink named init. See
man runit-init.
/sbin/runit
The heart of Runit. Started by runit-init. Starts the stage scripts. See
man runit.
/usr/sbin/sv
Controls the state of monitored services and reports their status. See
man sv.
/usr/sbin/chpst
Allows running a program with a changed process state. See man chpst.
/usr/sbin/utmpset
Records that a user has logged out. See man utmpset.
/usr/sbin/runsvchdir
Changes the current service directory. Used to change runlevels. See man
runsvchdir.
/usr/sbin/runsvdir
Starts a monitoring process for each subdirectory or symlink to a directory
in the current service directory (runlevel). See man runsvdir.
/usr/sbin/runsv
Starts and monitors a service. See man runsv.
/usr/sbin/svlogd
The logging daemon for Runit. Monitors log data and writes to specified log
files. See man svlogd.
Additional custom executables:
/sbin/ifup
A modified version of the LFS script to bring up network interfaces. It does
not rely on init-functions. See man ifup.
/sbin/ifdown
A modified version of the LFS script to bring down network interfaces. It
does not rely on init-functions. See man ifdown.
/lib/services/ipv4-static
A modified version of the LFS script to add a static IP address to network
interfaces. It does not rely on init-functions.
/lib/services/ipv4-static-route
A modified version of the LFS script to add a route to network interfaces.
It does not rely on init-functions.
/sbin/halt (poweroff,reboot)
From Void Linux, a custom binary executable to mimic the traditional
functions of halt for compatibility purposes. See man halt.
/sbin/shutdown
From Void Linux, a custom bash script to mimic the traditional function of
shutdown for compatibility purposes. See man shutdown.
/bin/pause
From Void Linux, a binary executable for pausing a script until a TERM
signal is received. Used to keep a script that normally runs and terminates
in a "running" state for the purposes of supervision. Otherwise, runsv would
restart the script over and over.
Config files:
/etc/runit.conf
The main configuration file for this runit-for-lfs project. It contains
variables and parameters for setting the system and hardware clocks,
timezone, console keymap and font, loading kernel modules, and creating
files that need to exist at boot time. See man runit.conf.
/etc/rc.local
A script run at boot time for the purpose of running commands or starting
starting services not covered by LFS or this runit-for-lfs project.
Directories:
/etc/runit
The main or parent directory for most of Runit's files and directories.
/etc/runit/runsvdir/single
A runlevel directory for administrative purposes that contains symlinks
only to agetty services for tty consoles.
/etc/runit/runsvdir/multi
The default runlevel for this runit-for-lfs project that contains symlinks
to agetty services and all other services that should be running at all
times.
/etc/runit/rc.d
A directory for users to store custom startup scripts.
/etc/sv
The directory for all service run, finish, and log run scripts.
Traditional LFS config files still utilized by runit-for-lfs:
/etc/rc.site
This runit-for-lfs project sources this file and uses several user-editable
variables and parameters from it if they are set there: SKIPTEMPCLEAN for
skipping the tmp directory cleanup, LOGLEVEL to change the console message
verbosity level, SYSKLOGD_PARMS to add parameters to the syslogd command run
in stage 1. This runit-for-lfs project has built in defaults for these if
they are null or not set.
/etc/hostname or /etc/sysconfig/network
This runit-for-lfs project tries both of these files to attempt to
determine the HOSTNAME string.
/etc/sysconfig/udev_retry
This runit-for-lfs project sources this file for a list of udev events that
should be retried after the filesystems have been mounted. Users should list
likely candidates for this here.
Acknowledgments and References
------------------------------
Updates to this may be acquired from the LFS-for-Runit project at...
http://www.linuxquestions.org/questions/linux-from-scratch-13/runit-for-lfs-official-bundle-release-4175511869
...or this SVN repository at...
https://code.google.com/p/runit-for-lfs
...or from the LinuxFromScratch Hints repository...
http://linuxfromscratch.org/hints/downloads/files
This project is loosely based on Void-Linux...
https://github.com/voidlinux/runit-void
...with several reworkings for Linux From Scratch.
http://www.linuxfromscratch.org
Richard Downing's Runit site was also very helpful to us...
http://www.langside.f2s.com/betterboot/
The originator of Runit is Gerrit Pape and his website is...
http://smarden.org/runitAbout
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