Bug 1885101 - systemd %post tries to create /etc/resolv.conf, fails in container
Summary: systemd %post tries to create /etc/resolv.conf, fails in container
Alias: None
Product: Fedora
Classification: Fedora
Component: systemd
Version: 33
Hardware: Unspecified
OS: Unspecified
Target Milestone: ---
Assignee: systemd-maint
QA Contact: Fedora Extras Quality Assurance
Depends On:
TreeView+ depends on / blocked
Reported: 2020-10-05 04:43 UTC by Martin Pitt
Modified: 2020-12-10 01:15 UTC (History)
11 users (show)

Fixed In Version: systemd-247~rc2-1.fc34 systemd-246.7-2.fc33
Doc Type: If docs needed, set a value
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Clone Of:
Last Closed: 2020-12-10 01:15:19 UTC
Type: Bug

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Description Martin Pitt 2020-10-05 04:43:50 UTC
Description of problem: systemd %post tries to overwrite an existing and working /etc/resolv.conf in a container with a symlink to resolved's file. "Fortunately" this fails:

  Running scriptlet: systemd-246.6-3.fc34.x86_64                                                                                  25/27 
ln: failed to create symbolic link '/etc/resolv.conf': Device or resource busy
warning: %post(systemd-246.6-3.fc34.x86_64) scriptlet failed, exit status 1

The %post script shouldn't fail, but it helps in this case as actually doing that would break DNS in the container. The script merely checks

   systemctl -q is-enabled systemd-resolved.service

which is true in a podman/docker application container (not full system container with pid 1 == systemd), but it will not actually run.

Instead, I suggest to check if ../run/systemd/resolve/stub-resolv.conf actually exists before linking to it (otherwise it's *definitively* going to break networking).

I'm not sure how reliable this EBUSY is, but let's rather not bet that it will always protect us.

Version-Release number of selected component (if applicable):


How reproducible: Always

Steps to Reproduce:
1. podman run -it --rm fedora:rawhide dnf install -y systemd

Actual results:

systemd %post fails

Expected results: systemd installs cleanly

Additional info:

Comment 1 Zbigniew Jędrzejewski-Szmek 2020-10-05 06:04:33 UTC
resolved might not be running when the scriplet is executed, so we can't rely on the presence of anything in /run.
But maybe we should check if the file is not a mountpoint too.

Comment 2 Zbigniew Jędrzejewski-Szmek 2020-11-17 15:53:23 UTC
Fixed in rawhide so far.

Comment 3 Fedora Update System 2020-12-08 19:43:49 UTC
FEDORA-2020-3616681a70 has been submitted as an update to Fedora 33. https://bodhi.fedoraproject.org/updates/FEDORA-2020-3616681a70

Comment 4 Fedora Update System 2020-12-09 02:21:01 UTC
FEDORA-2020-3616681a70 has been pushed to the Fedora 33 testing repository.
Soon you'll be able to install the update with the following command:
`sudo dnf upgrade --enablerepo=updates-testing --advisory=FEDORA-2020-3616681a70`
You can provide feedback for this update here: https://bodhi.fedoraproject.org/updates/FEDORA-2020-3616681a70

See also https://fedoraproject.org/wiki/QA:Updates_Testing for more information on how to test updates.

Comment 5 Fedora Update System 2020-12-10 01:15:19 UTC
FEDORA-2020-3616681a70 has been pushed to the Fedora 33 stable repository.
If problem still persists, please make note of it in this bug report.

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