Multiple instances of a daemon

Christopher Cowart ccowart at
Wed Nov 7 00:47:29 PST 2007


I want to be able to use the same rc script to start several instances
of a daemon. When I've encountered this desire before, I've cp'd the
script, given it a unique name, and carried on with my business. This is
a but kludgy and makes updating scripts a manual task.

Today, I realized the arpd port didn't provide an rc script, so I set
out to write one. I also knew that I was going to be launching several
different arpd's, so I wanted to figure out a better way to deal with
this problem.

I thought I'd be clever and use symlinks:
rc.d $ ls -l arpd*
-r-xr-xr-x 1 root wheel 486 Nov  7 00:01 arpd
lrwxr-xr-x 1 root wheel   4 Nov  6 23:32 arpd_vlan665 -> arpd
lrwxr-xr-x 1 root wheel   4 Nov  6 23:32 arpd_vlan679 -> arpd

Then I wrote my rc script with `name=${0##*/}'. Everything was fantastic
doing manual starts and stops. Then I tried rebooting...

After a few boots, some debugging, and a lot of tracing through /etc/rc
and /etc/rc.subr, I found the problem (or is it a feature?).
run_rc_script() sources the script. All the talk about not sourcing the
"current shell" anymore, and I foolishly assumed that meant something
more like calling the script and less like sourcing it in a subshell.

I would really find it convenient to use the symlink trick shown above,
because it means a symlink-compatible rc-script can be updated by the
port or mergemaster, and all the "copies" will "just work." I'd be
willing to take the time to implement something, but I don't pretend 
to know all the use cases or the motivation behind this design. 

One approach could be that run_rc_script() throws the rc script name
into a variable visible to the sourced script, say _rc_script_name. 
Then name could be something like `${_rc_script_name:-${0##*/}}' or a
less terse if/then.

Is this a feature other people would like to see, or is it just me?

Chris Cowart
Lead Systems Administrator
Network & Infrastructure Services, RSSP-IT
UC Berkeley
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