[Bug 1308378] Re: No working network after 12.04 LTS -> 14.04 LTS upgrade if no /etc/resolv.conf in precise
Steve Langasek
steve.langasek at canonical.com
Thu Apr 24 17:10:22 UTC 2014
On Thu, Apr 24, 2014 at 07:49:17AM -0000, Timo Jyrinki wrote:
> I think I know the actual reason (or one of those) it may be missing for
> many people including me in 12.04 LTS:
> https://help.ubuntu.com/community/LiveCDCustomization <- as an example,
> this in a modified form (just installing additional packages and
> resolv.conf as the only modified/removed file) was started to be used
> for Finnish Remix CD:s around 2007 and probably many other remixes have
> used the same wiki page as guidance. I'm not sure about the various more
> automated remix tools around. The instructions use copying host's
> resolv.conf to etc so that network works inside chroot, and then it
> "cleans up" by removing the copied /etc/resolv.conf. This was maybe ok
> when /etc/resolv.conf was not a symlink and Network Manager modified it
> directly, like in 10.04 LTS.
Ok. Would be great if someone could fix up such broken documentation; but
if you say this was because of a non-standard install method I'm satisfied
that there's no reason to expect a recurrence of the problem on upgrade.
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https://bugs.launchpad.net/bugs/1308378
Title:
Name resolving not working after 12.04 LTS -> 14.04 LTS if
/etc/resolv.conf was absent
Status in “resolvconf” package in Ubuntu:
Triaged
Status in “resolvconf” source package in Trusty:
Triaged
Bug description:
[Impact]
Name resolving using the NetworkManager-controlled nameserver
discontinues working after upgrading from 12.04 (precise) to 14.04
(trusty) in the case where /etc/resolv.conf is absent.
Precise works fine with that file absent because the resolver defaults
to using "nameserver 127.0.0.1" — so it is possible to run Precise for
a long time without even noticing that the file is absent.
In Trusty, resolving does not work if /etc/resolv.conf is absent
because the NetworkManager-controlled nameserver listens at 127.0.1.1.
People suffering from bug #1000244 may lack /etc/resolv.conf on
upgrade.
[Test Case]
1. Install 12.04 LTS
2. rm /etc/resolv.conf and observe everything works fine
3. update-manager -c -d
4. Observe that in 14.04 LTS name resolving does not work.
[Test Case for testing the fix on 14.04]
1. wget http://de.archive.ubuntu.com/ubuntu/pool/main/r/resolvconf/resolvconf_1.63ubuntu16_all.deb
2. dpkg -i resolvconf_1.63ubuntu16_all.deb
3. Running that precise version, test the possible cases like rm /etc/resolv.conf (note you lose name resolving at this point in 14.04)
4. Run 'bzr bd' (apt-get install bzr-builddeb first) in the proposed branch, dpkg -i ../build-area/*.deb
5. Check how either, depending on the case being tested, /etc/resolv.conf is intact / non-touched or it's created when not-existing, restoring network connectivity
[Regression Potential]
Seems low considering the limiting of the proposed fix to 12.04 ->
14.04 upgrades only, and only in the case of the user/3rd party
app/something intentionally removed /etc/resolv.conf (instead of just
modifying it).
---
I fixed it manually with:
cd /etc
sudo ln -s /run/resolvconf/resolv.conf .
It turns out 12.04 LTS works fine without /etc/resolv.conf, so that
increases the likelihoods that 12.04 LTS systems do not have that
file. When such a system is upgraded to 14.04 LTS, network seemingly
stops working to the user.
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