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Faster boot by running init.d scripts in parallel

One "hidden" feature of the current Debian boot sustem, is the ability
to run the init.d scripts in parallel.  This require dependency based
boot sequencing to be enabled, and the init.d script dependencies to
be complete and correct to work reliably.  The feature is hidden and
undocumented, because we plan to drop the CONCURRENCY variable in the
future and make concurrent booting the default when dependency based
boot sequencing is enabled.

If you want to test this feature in testing or unstable, use this

  echo CONCURRENCY=makefile >> /etc/default/rcS

It will enable makefile style concurrency, and run N scripts in
parallel during boot, where N is the number of CPUs or cores on the
machine.  This only work when dependency based boot sequencing.  This
can be enabled using

  dpkg-reconfigure insserv sysv-rc

If some services fail to work properly, the problem is most likely
because of bugs in the init.d script headers.  See
<URL: http://wiki.debian.org/LSBInitScripts/DependencyBasedBoot > for
clues on how to fix it.  Most scripts have correct enough dependency
information, but help is needed to find and fix the remaning few with
bugs.  Please make sure to usertag reported bugs to make them show up
<URL: http://bugs.debian.org/cgi-bin/pkgreport.cgi?usertag=initscripts-ng-devel@lists.alioth.debian.org >

If you want to improve boot speed even more, I recommend installing
the readahead-fedora packages, and boot once with the 'profile' kernel
option to adjust its readahead list to the list of files needed during

Happy hacking,
Petter Reinholdtsen

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