[Cooker] parallel init and LSB headers

[Olivier Blin]

Hi,

Thanks to the work from Couriousous, we're moving to a robust and fast
initialization system. As you've probably noticed, most of the
initscripts containing parallel initialization headers have been
converted to use LSB headers.

Here's a summary of the migration process to LSB headers in the
initscripts.

The previous X-Parallel-* tags of the parallel init system will be
abandonned soon, and prcsys (the parallel init process) has been
modified by Couriousous to support LSB dependencies.

So, it's now encouraged to use LSB headers to describe the
initscripts dependencies.


o Migration to LSB headers

Let's take the previous dm init script as an example.
It contained the following comments:
# chkconfig: 5 30 09
# description: This startup script launches the graphical display manager.
# X-Parallel-Init
# X-Parallel-Requires: xfs network harddrake

We can add LSB headers in a block delimited by the following lines:
### BEGIN INIT INFO
### END INIT INFO

X-Parallel-Provides tags should be converted to Provides tags, to
describe a dependency facility.

# Provides: dm

The services should preferably be named using this policy:
http://www.lanana.org/lsbreg/init/init.txt

X-Parallel-Requires tags have to be converted to Required-Start
(mandatory service) or Should-Start (optionnal service) tags.

# Required-Start: xfs
# Should-Start: $network harddrake

Dependency facilities that begin with a '$' sign are reserved system
facilities, such as $network. A complete list is available here:
http://www.linuxbase.org/spec/booksets/LSB-Core-generic/LSB-Core-generic/facilname.html

If another service has to be available during stop, the mandatory
dependency should be described using a Required-Stop tag (this is an
example, it may not be true):
# Required-Stop: xfs

The same is available for optionnal dependencies, using the
Should-Stop flag.

You can specify which runlevels the service should be started in using
the Default-Start tag.
# Default-Start: 5

Descriptions have to be provided using the Short-Description and
Description (potentially multi-line) tags:
# Short-Description: Launches the graphical display manager
# Description: This startup script launches the graphical display
# manager.

The dm initscript will finally end up with the following LSB header:

### BEGIN INIT INFO
# Provides: dm
# Required-Start: xfs
# Required-Stop: xfs
# Should-Start: $network harddrake
# Default-Start: 5
# Short-Description: Launches the graphical display manager
# Description: This startup script launches the graphical display manager.
### END INIT INFO


o Interactive initscripts

Some initscripts request some user input, such as harddrake when a new
device is found.
These scripts used the X-Parallel-Interactive tag.
Since this will be quite Mandriva specific, we will now use the
X-Mandriva-Interactive tag, since the LSB asks for an
X-implementor-extension format.
# X-Mandriva-Interactive

Mandriva should probably request a vendor tag to the Linux Assigned
Names And Numbers Authority, see:
http://www.lanana.org/lsbreg/providers/providers.txt


o References

For a more complete reference about the LSB headers, please see:
- LSB specs
http://www.linuxbase.org/spec/booksets/LSB-Core-generic/LSB-Core-generic/tocsysinit.html
http://refspecs.freestandards.org/LSB_3.1.0/LSB-Core-generic/LSB-Core-generic/tocsysinit.html
- Suse initscripts specs
http://forgeftp.novell.com/library/SUSE%20Package%20Conventions/spc_init_scripts.html
- Linux Assigned Names And Numbers Authority
http://www.lanana.org/
- Parallel Init on the wiki
http://qa.mandriva.com/twiki/bin/view/Main/Pinit



Adding LSB headers will allow to have a robust services dependency
check, and to provide a base for parallel initialization, so packagers
are all encouraged to add LSB headers to their pacakges.

Thanks again to Couriousous for his time and all the remarks that
helped to improve this system!
(and allowed me to write this small document and start the work)


Regards

-- 
Olivier Blin - Mandriva