Migrating the insserv enabling stuff from insserv to sysv-rc

[Petter Reinholdtsen]

[Petter Reinholdtsen]
> This of course need to be done carefully, to make sure the systems
> with insserv enabled, stay enabled.

I am still working on this, and have come up with a modified plan.  I
am not happy with leaving the /usr/sbin/update-rc.d-insserv script
behind, but I am unable to figure out a way to avoid that while still
keeping update-rc.d working during the upgrade/migration.

For the next insserv upload, version 1.12.0-11:

  - Conflict with sysv-rc (<= 2.87dsf-2), to make sure it is not
    possible to upgrade insserv without upgrading sysv-rc too.
  - Drop the depend on sysv-rc to avoid a dependency loop.
  - Also drop the dependencies on initscripts and sysvinit-utils
    previously used to make sure scripts supporting insserv enabled
    boot was used, and let sysv-rc handle this.
  - Drop all code in postinst++ to enable insserv, including
    update-bootsystem-insserv and update-bootsystem-insserv.8.
  - Do not touch the divert of /usr/sbin/update-rc.d, and keep
    /usr/sbin/update-rc.d-insserv to avoid a dangling symlink during
    upgrade.
  - Keep the file /var/lib/insserv/using-insserv to indicate that
    dependency based boot sequencing is enabled.

For the next sysv-rc upload, version 2.87dsf-3:

  - Move the still active code in update-bootsystem-insserv from
    insserv to the sysv-rc postinst.
  - Rewrite update-rc.d to include the code in update-rc.d-insserv and
    use it when /var/lib/insserv/using-insserv exist.  This mean we
    can drop the divert previously done by insserv postinst using
    update-bootsystem-insserv.
  - Rewrite the postinst++ to remove the insserv divert of
    /usr/sbin/update-rc.d if it exist.
  - Rewrite postinst++ to enable insserv if it is safe to do so, and
    drop the code to migrate back.  Flag the migration using
    /var/lib/insserv/using-insserv.
  - Make sure sysv-rc depend on new enough initscripts (>=
    2.86.ds1-63) and sysvinit-utils (>= 2.86.ds1-62) packages for
    dependency based boot sequencing to work.
  - Update the dependency on insserv to (>> 1.12.0-10), to get a
    version without the enabling stuff.

This should still make sure systems using sysv-rc with insserv keep
using sysv-rc with insserv during and after the upgrade.  I am still
stuck with the /usr/sbin/update-rc.d-insserv script left behind in the
insserv package, and I assume it will only be safe to remove in
Squeeze+1 (or +2 if we are to support skipping a version during
upgrades).

I'm not sure I really need the conflict.

Did I forget anything?

If I understand this correctly, the upgrade when insserv is enabled,
will be done in this sequence, and each ... represent when other
packages might be configured and a working update-rc.d need to be
provided.

  Unpack insserv
   - symlink to /usr/sbin/update-rc.d-insserv is kept
  ...
  Unpack sysv-rc
   - provides /usr/sbin/update-rc.d which work with insserv
  ...
  Configure insserv
  ...
  Configure sysv-rc
   - divert to /usr/sbin/update-rc.d-insserv is removed

Happy hacking,
-- 
Petter Reinholdtsen