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Revision 1 as of 2005-08-24 10:55:08
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Editor: anonymous
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Revision 18 as of 2007-06-15 20:07:41
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Editor: ?PetterReinholdtsen
Comment: Mention the new X-Start-Before and X-Stop-After keywords.
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This is a short documentation about how to make an Init Script LSB-compliant. Most of this page has been pulled 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]. 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:
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This page is a quick and dirty draft. It is based on the content in
<URL:http://refspecs.freestandards.org/LSB_2.1.0/LSB-generic/LSB-generic/initscrcomconv.html>.
Is it recommended to read if you want to know more.
 * provide, at least, the following actions: start, stop, restart, force-reload, and status. All of those, except for, status, are required by the [http://www.debian.org/doc/debian-policy/ch-opersys.html#s9.3.2 Debian Policy, chapter 9.3.2 Writing the scripts]. "Status" support has been requested into policy, see [http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=291148 #291148].

 * return proper exit status codes.
 * document runtime dependencies.
 * [optionally] Log messages using the Init.d functions: log_success_msg, log_failure_msg and log_warning_msg (This would introduce consistent output in scripts, as requested in [http://lists.debian.org/debian-devel/2005/06/msg00729.html]
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 information 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])


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  ### BEGIN INIT INFO
  # 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.
  ### END INIT INFO
### BEGIN INIT INFO
# 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.
### END INIT INFO
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All sections except the description-sections are space separate lists. The block shown above has a special rigid format delimited by the lines
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Provides should list the name of this service, normally the script name but might also list the name of services it "replaces". {{{
### BEGIN INIT INFO
### END INIT INFO
}}}
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Required-Start are services needed to start this service. These services must start before this service. Required-Stop are services used by this service, and this service should stop before the listed services are stopped. where all trailing spaces shall be ignored. On the other hand, all lines inside the block shall be of the form
{{{
# {keyword}: arg1 [arg2...]
}}}
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Should-Start are services that if present should start before this service, but this service can start if the listed services are missing. Should-Stop are services that if present should be stopped after this service. 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
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Default-Start is the run levels where this service should be started by default, and Default-Stop is the run levels where this service should be stopped by default.
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Description and short-description are fairly obvious. '''Provides: boot_facility_1 [boot_facility_2...]'''
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For dependency tracking, the required-''' and should-''' are important, and the rest is unused. The default runlevels are used by 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.     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.
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There are some "virtual"''system service names, listed in <URL:http:''/refspecs.freestandards.org/LSB_2.1.0/LSB-generic/LSB-generic/facilname.html>.
'''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 facilities 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 facilities 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 facilities 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]].
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|| $all || 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.
Suse implemented X-Start-Before and X-Stop-After in insserv 1.09.0.
Debian could and should use the same keywords.


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.

Question: What is a "proper" exit status code? Looking at [http://bugs.debian.org/208010 #208010,] this seems rather controversial. Non-zero exit codes might even cause breakage, and the LSB conflicts with Debian policy here.

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 information 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):

### BEGIN INIT INFO
# 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.
### END INIT INFO

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

### BEGIN INIT INFO
### END INIT INFO

where all trailing spaces shall be ignored. On the other hand, all lines inside the block shall be 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 facilities 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 facilities 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 facilities 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:

$local_fs

all local filesystems are mounted

$network

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

$named

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

$portmap

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

$remote_fs

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.

$syslog

system logger is operational

$time

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.

$all

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. Suse implemented X-Start-Before and X-Stop-After in insserv 1.09.0. Debian could and should use the same keywords.

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.

Question: What is a "proper" exit status code? Looking at [http://bugs.debian.org/208010 #208010,] this seems rather controversial. Non-zero exit codes might even cause breakage, and the LSB conflicts with Debian policy here.