Removing package fails to remove user

It does already but only if deluser tool is available.

However, this is a minor bug because normally it does not hurt even if the user account remains on the system.

Why this you might ask? Because the installation normally does not fail since it's a system user account. Unless... somebody (YOU?) messed around with user id so it doesn't look like a system account anymore and in this case adduser can show erroneous behavior. Also see Debian bug #708073 .

Ah, I had no idea that it mattered if the user had a system id. It's very possible that my configuration management mucked about with the user id (or maybe even created the user instead of the package creating the user).

Thanks for clearing up the source of the error.

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@Eduard: any reason why this can't be done via Debian?

It's not entirely clear that the apt-cacher-ng user *should* be removed on package removal. See http://wiki.debian.org/AccountHandlingInMaintainerScripts for unresolved discussion of such ☺.

It's also worth noting that the patch as written will fail if adduser is installed *and* the apt-cacher-ng user is not a system user. You've traded an error on reinstall for an error on removal.

I've fixed a similar problem in colord recently by just checking whether the user exists before trying to create it in the postinst.

Finally, this does indeed seem like something that would also apply to debian - have you filed a Debian bug or contacted the maintainer about this?

This bug was fixed in the package apt-cacher-ng - 0.7.14-1

---------------
apt-cacher-ng (0.7.14-1) unstable; urgency=low

  * New upstream version
    + prevents background looping (closes: #703296)
    + stop spamming apt-cacher.err when verbosity is not set to debug mode
      (closes: #714146)
  * Remove system user account with bare passwd tools where adduser package
    has been removed before purging apt-cacher-ng (LP: #1185547)

 -- Eduard Bloch <email address hidden> Sat, 20 Jul 2013 10:55:07 +0200