/etc/init.d structure
There was a discussion about this recently... So I thought I'd mention this:
This is posted on cola; looks neat to me:
-----------------------------------------
From: Winfried Truemper <winni@xpilot.org>
Newsgroups: comp.os.linux.announce
Subject: r2d2 - reading runlevels in 2 dimensions
The traditional "SysV" scheme of implementing runlevels uses links
distributed over several directories under "/etc/rc?.d/*". The main
problem with the links is that you can't easily get a survey of your
setup. Yes, you can write a script like the one accompanied with this
package but this is not satisfactory because it's another layer
(another name of a program to know) and not editable.
I rewrote the "rc"-program so it handles _one_ config file instead of
many links in "/etc/rc?.d/*". Apart from the IMHO more intuitive
configuration file it's fully compatible with the traditional SysV
scheme. You can always fetch the newest version from
ftp://www.shop.de/linux/local and soon from sunsite.
Here's an extract from a sample config file:
# This is the configuration file for /etc/init.d/runlevel.conf
#
#format:
#<sort> <off> <on> <script>
05 - 0 /etc/init.d/halt
05 - 1 /etc/init.d/single
05 - 6 /etc/init.d/reboot
10 0,1,6 2,3,4,5 /etc/init.d/sysklogd
12 0,1,6 2,3,4,5 /etc/init.d/kerneld
[..]
89 0,1,6 2,3,4,5 /etc/init.d/cron
99 - 2,3,4,5 /etc/init.d/rmnologin
99 0,1,6 2,3,4,5 /etc/init.d/xdm
The syntax should be fairly obvious:
* comments begin with the numbersign #
* The first column is a criteria for inserting new entries.
As there is no consens about a numbering scheme among
systems claiming themselves to be SysV compatible,
these numbers are not very useful but kept for higher
psychological compatibility.
* The second column consists of a comma-seperated list of
runlevels in which the script should be switched "off"
- or -
a single "-" if the script should never be stopped (with
that sort-number).
* The third column consists of a comma-seperated list of
runlevels in which the script should be switched "on"
- or -
a single "-" if the script should never be started (with
that sort-number).
* The last column specifies the full name of the script.
"r2d2" uses built-in bash functions only and does not rely on any
external program installed (my highest principle is: if you need to
fork, something is messed up). Performance is quite good because
evaluating a single file is faster than several hundred symbolic links
under /etc. On my old 486/66 the delay between starting "r2d2" and
the first script executed is about 2 seconds.
A script named rclink2file.sh to convert your current link-setup into
a configuration file is available as well as an almost compatible
"update-rc.d"-program. To edit the configuration file you can use your
favourite editor. :-)
After unpacking the tar file you may want to try it out by issuing the
commands
./rclink2file.sh > runlevel.conf
export PRELEVEL=N # previous runlevel, N = Booting
./r2d2 2 # "switch" to runlevel "2"
You don't need to be root to do this and to be on the save side,
"r2d2" only prints the commands it would execute for now.
IMPORTANT NOTE: if you like the alternate method you should think
carefully about potential incompabilities with your distribution and
potential problems with upgrading before you replace the old one.
The disadvantages (which don't apply to the method with links) as far
as I can see them:
* Modifications require the whole file to be rewritten, which
is a source for errors. On the other side this is only as bad
as with /etc/passwd.
* Inserting and removing entries is not done via
"well-understood" utilities like "ln" and "rm". On the other
side the scheme with links is not widely understood at all,
so "ln" and "rm" don't really help.
* The "sort numbers" are not evaluated by "r2d2".
* Only very few system administrators (mad or heros?) have
reported the usage of "r2d2" in a production environment
to me, so the testbed is very small.
Advantages beside the easeness:
* You can easily make backups of the config file and use
standard software like "diff" to compare "working" and
"not working" configuration files. Try that with a bunch
of several hundred symlinks.
* The "sort numbers" are not evaluated by "rc". :-)
* No special tool required, you can use your favorite editor
to maintain the configuration manually.
* Symbolic runlevels like "reboot" can be easily supported
(although the numbers are more comprehensive).
* The sort-numbers could be replaced by symbolic names, too.
* "Update-rc.d" is quite fast (2-3s on an old ISA-486 = up to
10 times faster than the old one).
Of course even more complicated setups can be expressed in the
configuration file:
#Format:
#<sort> <on-> <off-levels> <script>
15 0 - /etc/init.d/foo
17 1 - /etc/init.d/foo
19 6 - /etc/init.d/foo
14 - 5 /etc/init.d/foo
80 - 2 /etc/init.d/foo
84 - 3,4 /etc/init.d/foo
A man-page is planned for future releases. The mailinglist for
discussion is r2d2@shop.de, which has an archive under
http://www.shop.de/linux/archives/r2d2. To subscribe send an email
with the text "subscribe" to r2d2-request@shop.de, e.g. by executing
echo "subscribe" | mail r2d2-request@shop.de.
- -Winfried
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