Date: Wed, 7 Nov 2007 08:48:03 -0500 From: Bill Moran <wmoran@collaborativefusion.com> To: Christopher Cowart <ccowart@rescomp.berkeley.edu> Cc: freebsd-rc@FreeBSD.org Subject: Re: Multiple instances of a daemon Message-ID: <20071107084803.6a3564db.wmoran@collaborativefusion.com> In-Reply-To: <20071107082837.GM65098@hal.rescomp.berkeley.edu> References: <20071107082837.GM65098@hal.rescomp.berkeley.edu>
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In response to Christopher Cowart <ccowart@rescomp.berkeley.edu>:
> Hello,
>
> 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?
The canonical way of doing this has been a "profiles"-enabled rc
script. See the Apache or Slony rc scripts for examples.
Not sure if your approach might be better.
--
Bill Moran
Collaborative Fusion Inc.
http://people.collaborativefusion.com/~wmoran/
wmoran@collaborativefusion.com
Phone: 412-422-3463x4023
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