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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:

• 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 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])

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].

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 show above has a special rigid format delimited by the lines

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

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, 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 also use the name of the service(s) that the script replaces.

Required-Start: boot_facility_1 [boot_facility_2...],Required-Stop: boot_facility_1 [boot_facility_2...]

• defines 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.

Should-Start: boot_facility_1 [boot_facility_2...],Should-Stop: boot_facility_1 [boot_facility_2...]

• defines the 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.

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

• 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.

Short-Description: short_description, Description: multiline_description

• Description and short-description are fairly obvious.

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.

There are some "virtual"/system service names, listed in the [http://refspecs.freestandards.org/LSB_3.0.0/LSB-Core-generic/LSB-Core-generic/facilname.html [LSB 3.0]]. These are:

Frequent questions

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

Answer: There is header specified in the LSB allowing this to be expressed. It is allowed to add extra (X-) headers, so we could add this expression if needed.

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

Answer: There is no such standard-defined header. 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 ourself.

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.