Differences between revisions 12 and 13
Revision 12 as of 2006-07-08 13:31:23
Size: 8864
Editor: ?CarlosVillegas
Revision 13 as of 2006-07-14 07:43:55
Size: 8996
Editor: ?PetterReinholdtsen
Comment: Document $all.
Deletions are marked like this. Additions are marked like this.
Line 112: Line 112:
|| $all || facility supported by insserv to start a script after all the other scripts, at the end of the boot sequence. ||

How to LSBize an Init Script

This is a short documentation about how to make an Init Script LSB-compliant based on the [http://refspecs.freestandards.org/LSB_3.1.0/LSB-Core-generic/LSB-Core-generic/tocsysinit.html [Chapter 20 of the LSB 3.1]]. LSB-compliant init scripts need to:

and should also follow [http://www.debian.org/doc/debian-policy/ch-opersys.html#s9.4 Debian Policy, chapter 9.4 Console messages from init.d scripts])

Full informantion on the actions (and return codes) that LSB scripts have to honor are available at [http://refspecs.freestandards.org/LSB_3.1.0/LSB-Core-generic/LSB-Core-generic/iniscrptact.html LSB 3.1, Chapter 20.2. Init Script Actions]. Maintainers should review that section and review / adjust their init.d scripts accordingly.

Run-time dependencies

By documenting the run-time dependencies for init.d scripts, it becomes possible to verify the current boot order, and also to run boot scripts in parallel to speed up the boot process (This is on the [http://wiki.debian.org/EtchTODOList TODO list for Etch])

Add a block like this in the init.d script (example based on xdebconfigurator):

# Provides:          xdebconfigurator
# Required-Start:    $syslog
# Required-Stop:     $syslog
# Should-Start:      $local_fs
# Should-Stop:       $local_fs
# Default-Start:     2 3 4 5
# Default-Stop:      0 1 6
# Short-Description: Generate xfree86 configuration at boot time
# Description:       Preseed X configuration and use dexconf to
#                    generate a new configuration file.

The block show above has a special rigid format delimited by the lines


where all traling spaces shall be ignored. On the other hand, all lines inside the block shall of the form

# {keyword}: arg1 [arg2...]

and begin with a hash character '#' in the first column followed by one single space, except for the lines following the Description keyword. The following keywords are defined

Provides: boot_facility_1 [boot_facility_2...]

  • defines boot facilities provided by this init script such that when the script is run with the start argument, the specified boot facilities will be deemed present and hence other init scripts which require those boot facilities will be started at a later stage. Normally you can use the script name as boot facility but you can also use the name of the service(s) that the script replaces. Besides, consider using virtual facility names as described below if the script provides one or more of them.

Required-Start: boot_facility_1 [boot_facility_2...]

  • defines facilities that must be available to start the script. Consider using virtual facility names as described below if adequate. If no boot facility is specified it means that this script can be started just after the bootstrap without local filesystems mounted, nor system logger, etc.

Required-Stop: boot_facility_1 [boot_facility_2...]

  • defines facilites used by the service provided by the script. The facility provided by this script should stop before the listed facilities are stopped to avoid conflicts. Normally you would include here the same facilites as for the Required-Start keyword.

Should-Start: boot_facility_1 [boot_facility_2...]

  • defines the facilities that if present should start before the service provided by the script. Nevertheless, the script can still start if the listed facilities are missing. This allows for weak dependencies which do not cause the service to fail if a facility is not available. Consider using virtual facility names as described below if adequate.

Should-Stop: boot_facility_1 [boot_facility_2...]

  • defines the facilities that if present should be stopped after this service. Normally you would include here the same facilites as those used with the Should-Start keyword.

Default-Start: run_level_1 [run_level_2...],Default-Stop: run_level_1 [run_level_2...]

  • defines the run levels where the script should be started (stopped) by default. For example, if a service should run in runlevels 3, 4, and 5 only, specify "Default-Start: 3 4 5" and "Default-Stop: 0 1 2 6".

Short-Description: short_description

  • provide a brief description of the actions of the init script. Limited to a single line of text.

Description: multiline_description

  • provide a more complete description of the actions of the init script. May span multiple lines. In a multiline description, each continuation line shall begin with a '#' followed by tab character or a '#' followed by at least two space characters. The multiline description is terminated by the first line that does not match this criteria.

For dependency tracking, the provides, required- and should- keywords are important, and the rest is unused. The default runlevels are used by a program to order the init scripts (e.g. insserv) to keep track of which rc#.d directory to update when a service is added for the first time, and should reflect the intent of the service.

There are some "virtual" facility names, listed in the [http://refspecs.freestandards.org/LSB_3.1.0/LSB-Core-generic/LSB-Core-generic/facilname.html [LSB 3.1]]. These are:


all local filesystems are mounted


low level networking (ethernet card; may imply PCMCIA running)


daemons which may provide hostname resolution (if present) are running. For example, daemons to query DNS, NIS+, or LDAP.


daemons providing ["SunRPC"]/ONCRPC portmapping service as defined in RFC 1833 (if present) are running all remote


filesystems are mounted. In some LSB run-time environments, filesystems such as /usr may be remote. Many applications that require $local_fs will probably require also require $remote_fs.


system logger is operational


the system time has been set, for example by using a network-based time program such as ntp or rdate, or via the hardware Real Time Clock.


facility supported by insserv to start a script after all the other scripts, at the end of the boot sequence.

Other (non-system) facilities may be defined by other applications. These facilities shall be named using the same [http://refspecs.freestandards.org/LSB_3.1.0/LSB-Core-generic/LSB-Core-generic/etc.html#FHS-NAME-RULES conventions defined for naming init scripts].

Most of this section was originally based from a [http://lists.debian.org/debian-devel/2005/08/msg01172.html message by Petter Reinholdtsen] on [http://lists.debian.org/debian-devel Debian-devel].

Frequent questions

Question: Is it possible to start a given init script as late as possible?

Answer: yes, if you really want to do so, insserv recognises the $all virtual facility name such that the script will be executed at the end.

Question: Is it possible to add extra keywords?

Answer: If there is no current keyword you could use for your needs, the LSB allows for local extensions using the prefix X-. For example, X-Debian-foobardecl or X-Ubuntu-fastdecl.

Question: Is it possible to specify that a given script should start before another script?

Answer: There is no such standard-defined header. The LSB approach would be to get the second script to include your given script in its Required-Start arguments. Besides, we could define a debian specific extention to express this, but there is no implementation using such header, so we would have to implement it ourselves.

Question: Shouldn't I wait until the Debian policy changes?

The Debian policy changes are slow to introduce even for things (for an example, see [http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=291148 #291148]) which most maintainers agree are good since we have to wait first for many packages to do things in the same way before turning it into policy. Since we want to be LSB compliant, init.d scripts can be adjusted now to be LSB compliant.