Re: Need advice wrt #295306

[Frank Küster <frank@debian.org>]

Pierre Habouzit <pierre.habouzit@m4x.org> wrotee:

> The only way is to do some hackish things in the <new-preinst> since 
> it's the only script that will be called before the buggy <old-postrm>
>
> until here, it's OK. but I readlly dunno which hack I have to implement 
> int the preinst. I have (at least) two choices, but I don't like any of 
> them :
>  (1) rm -f /var/lib/dpkg/info/uw-imapd.postrm (with the appropriate
>      version check)
>   - : this is truely horrible, moreover, postrm files may live elsewhere

Where should they live?

>   - : this removes a dpkg file during it runs ... dpkg cannot be blamed
>       if he fails after such a thing
>   + : this is small, and easy to understand

I would never do such things.

>  (2) parse /etc/inetd.conf and put the entries I don't want to loose
>      somewhere in /var/cache for a moment
>      and then use it in the postinst to feed inetd.conf
>   + : this is really cleaner than the previous
>   - : this is really not trivial : inetd.conf is sorted by categories,
>       and it will be really difficult to put the entries at the right
>       place in the postinst
>   - : this fix will use quite a big amount of code, touch to many
>       scripts, and thereof may lead to new bugs, really more easily than
>       the previous "solution"
>
> I can't see any (3) that isn't a new instance of (1) or (2), so any 
> advice is welcome.

I still think that (2) is the way to go.  I also do not see that it is
_so_ difficult.  This is what I would do:

1. Grep only non-comment, non-empty lines from inetd.conf

2. grep for the lines that uw-imapd is going to handle in its postinst.

3. For each line you got, add a comment line after it to inetd.conf:

tempfile=`mktemp`
sed -e "/^$service/ a #uw-imapd preinst: $original_line_as_grepped" \
  /etc/inetd.conf > $tempfile
chmod --reference /etc/inetd.conf $tempfile
chown --reference /etc/inetd.conf $tempfile
mv $tempfile /etc/inetd.conf # you might need "-f"

(alternatively, you can use in-place-editing, but I am quite sure
woody's sed can't do that, and you don't want a pre-depends. woody's
Perl probably can do it.)

As far as I can see, nobody will touch these lines between your preinst
and your postinst, because the buggy postrm will only act on lines
matching ^$service.

In postinst, do the following:

sed -e 's@^#uw-imapd preinst: @@'

The only pitfall I see is that you must make sure that no char from the
original line as grepped prematurely ends your "a" command to sed. Maybe
Perl is safer here.

Regards, Frank
-- 
Frank Küster
Inst. f. Biochemie der Univ. Zürich
Debian Developer