default network autostart symlink recreated

[Jamin W. Collins]

===================================================
SRU Justification:
1. Impact: if admins disable the example default network, then each libvirt upgrade re-enables it
2. Development fix: use a patch in debian to not install the default network auto-run symlink, and tweak postinst to create it (only) on a first install.
3. Stable fix: same as development fix
4. Test case:
 a. sudo apt-get install libvirt-bin
 b. sudo rm /etc/libvirt/qemu/network/defaults/autostart.xml
 c. sudo apt-get install --reinstall libvirt-bin
 d. ls -l /etc/libvirt/qemu/network/defaults/autostart.xml
   After reinstall, autostart should not exist.
5. Regression Potential: a mistake in the postinst script could cause installations and upgrades to fail.
===================================================
Periodically the autostart symlink for libvirt-bin's default network is recreated. This is not expected or desired behavior. I've manually removed the symlink repeatedly as I've created my own network definitions that I'd prefer were started instead.

ProblemType: Bug
Architecture: amd64
DistroRelease: Ubuntu 9.04
NonfreeKernelModules: nvidia ath_hal
Package: libvirt-bin 0.6.1-0ubuntu6
ProcEnviron:
 PATH=(custom, user)
 LANG=en_US.UTF-8
 SHELL=/bin/bash
SourcePackage: libvirt
Uname: Linux 2.6.28-11-generic x86_64
UnreportableReason: This is not a genuine Ubuntu package

[Chuck Short (zulcss)]

Thank you for taking the time to report this bug and helping to make Ubuntu better. Please answer these questions:
1. Is this reproducible?
2. If so, what specific steps should we take to recreate this bug? Be as detailed as possible.
This will help us to find and resolve the problem.

[Jamin W. Collins (jcollins)]

Steps to reproduce:

Create additional network definitions. I have the following (all set to start on boot):
- public_1, 192.168.51.0/24, 192.168.51.128, 192.168.51.254, w/NAT
- private_1, 192.168.61.0/24, 192.168.61.128, 192.168.61.254, isolated
- private_2, 192.168.62.0/24, 192.168.62.128, 192.168.62.254, isolated

Disable the default network definition (uncheck Autostart and Apply).

Verify that the symlink for starting the default network definition is no longer present:

ls -l /etc/libvirt/qemu/networks/autostart/

Install, or reinstall, the libvirt-bin package or any update to the package. The symlink for the default network autostart is restored.

[Jamie Strandboge (jdstrand)]

Jamin, is the network recreated if you undefine the default network with:
$ virsh net-destroy default
$ virsh net-undefine default

[Jamin W. Collins (jcollins)]

I don't want them undefined or removed, only not set to auto start.

[Alvin (alvind)]

Every time you create a virtual machine, using virt-manager, it will be started again. Maybe that's the case here?

[Adam Conrad (adconrad)]

This is happening because the package is shipping the symlink as a conffile. Generally speaking, this isn't a great idea, and dpkg's handling of symlink-as-conffile cases is shockingly non-obvious.

Like most packages with symlink trees in /etc, what this should be doing is not shipping the symlink as a file, but rather creating it in the postinst on new installs (and only new installs), so a sysadming choosing to remove the symlink won't have to worry about it coming back spontaneously.

[Simon Déziel (sdeziel)]

I am also annoyed by that behaviour after every update of the package. Adam's analysis in comment #7 is right and I think its suggestion should be implemented.

[Serge Hallyn (serge-hallyn)]

Thanks Simon and Adam, what you suggest sounds reasonable.

Do you mind raising this as a bug against the debian package? (If you do, I'll go ahead and do it).

[Simon Déziel (sdeziel)]

Serge, you seem to have addressed this in Precise (http://changelogs.ubuntu.com/changelogs/pool/main/libv/libvirt/libvirt_0.9.7-2ubuntu2/changelog). Would that be possible to do a SRU for Lucid ? I'd like to test your fix on Precise but I lack a test setup ATM.

Thanks for addressing this anyways.

[Simon Déziel (sdeziel)]

Oops, I misread the fix that in fact no longer apply the patch.

[Serge Hallyn (serge-hallyn)]

@Simon,

do you think we should be applying debian/Don-t-enable-default-network-on-boot.patch?

[Serge Hallyn (serge-hallyn)]

Ah, I see. Enabling only that patch breaks automatic net setup on new installs. So to fix this bug, we should enable that patch and fix postinst to create the symlink on new install.

[Serge Hallyn (serge-hallyn)]

I do think that fix should be SRU-able, but I want to do a whole lot of testing of new installs and upgrades before committing that fix.

[Serge Hallyn (serge-hallyn)]

Here is the debdiff I"m proposing to fix this bug. It tests fine for me - new installs get the default network autostart symlink, upgrades do not.

[Launchpad Janitor (janitor)]

This bug was fixed in the package libvirt - 0.9.7-2ubuntu3

---------------
libvirt (0.9.7-2ubuntu3) precise; urgency=low

  * Don't override local removal of default network autostart on upgrades
    (LP: #372001)
    - re-enable debian/Don-t-enable-default-network-on-boot.patch
    - debian/libvirt-bin.postinst: create default network autostart symlink
      for new installs only.
 -- Serge Hallyn <email address hidden> Thu, 01 Dec 2011 21:55:01 +0000

[Serge Hallyn (serge-hallyn)]

My postinst patch was bad. I will re-upload a proper fix after it gets more testing in precise.

[Simon Déziel (sdeziel)]

Serge, sorry for the late reply, I forgot to subscribe. I'll be available to test both upgrade and fresh install behaviour of your patch when it will be ready.

[Serge Hallyn (serge-hallyn)]

@Simon,

thanks. As everyone (including SRU team) will likely be out for a good chunk of the rest of the month, do you mind if we wait until early january to do it?

I'm fine either way, but would prefer this not to slip through the cracks or get out of sync on account of the holidays.

[Simon Déziel (sdeziel)]

Works for me as the problem only manifests when updating libvirt and if the SRU team will be out for holidays there shouldn't be any update causing the default network to "re-appear".

[Simon Déziel (sdeziel)]

@Serge, whenever you are ready for this I'll be available to test, thanks.

[Serge Hallyn (serge-hallyn)]

Thanks Simon, I want to do extensive testing myself first (since I messed up the first time), but will aim to get this uploaded today. Hopefully it will hit the archive tomorrow.

[Martin Pitt (pitti)]

Hello Jamin, or anyone else affected,

Accepted libvirt into oneiric-proposed, the package will build now and be available in a few hours. Please test and give feedback here. See https://wiki.ubuntu.com/Testing/EnableProposed for documentation how to enable and use -proposed. Thank you in advance!

[Simon Déziel (sdeziel)]

libvirt version 0.9.2-4ubuntu15.2 fixes the issue on Oneiric. Many thanks.

[Launchpad Janitor (janitor)]

This bug was fixed in the package libvirt - 0.9.2-4ubuntu15.2

---------------
libvirt (0.9.2-4ubuntu15.2) oneiric-proposed; urgency=low

  * Don't override local removal of default network autostart on upgrades
      (LP: #372001)
    - re-enable debian/Don-t-enable-default-network-on-boot.patch
    - debian/libvirt-bin.preinst: note if the symlink exists
    - debian/libvirt-bin.postinst: if symlink existed, OR if we are upgrading
      from one of the broken versions, then recreate the symlink. (Continue
      to create the symlink on new installs.)
 -- Serge Hallyn <email address hidden> Mon, 23 Jan 2012 11:12:51 -0600

[Clint Byrum (clint-fewbar)]

Hello Jamin, or anyone else affected,

Accepted libvirt into lucid-proposed. The package will build now and be available in a few hours. Please test and give feedback here. See https://wiki.ubuntu.com/Testing/EnableProposed for documentation how to enable and use -proposed. Thank you in advance!

[Simon Déziel (sdeziel)]

libvirt version 0.7.5-5ubuntu27.22 fixes the issue on Lucid. Many thanks.

[Launchpad Janitor (janitor)]

This bug was fixed in the package libvirt - 0.7.5-5ubuntu27.22

---------------
libvirt (0.7.5-5ubuntu27.22) lucid-proposed; urgency=low

  * Don't override local removal of default network autostart on upgrades
      (LP: #372001)
    - re-enable debian/Don-t-enable-default-network-on-boot.patch
    - debian/libvirt-bin.preinst: note if the symlink exists
    - debian/libvirt-bin.postinst: if symlink existed, OR if we are upgrading
      from one of the broken versions, then recreate the symlink. (Continue
      to create the symlink on new installs.)
 -- Serge Hallyn <email address hidden> Mon, 23 Jan 2012 10:15:56 -0600