swap file unsuitable for btrfs

Bug #1884161 reported by ov2k
This bug affects 1 person
Affects Status Importance Assigned to Milestone

Bug Description

There is a corresponding ubiquity bug:

To summarize, installing Ubuntu 20.04 LTS to a btrfs filesystem causes systemd to report a degraded system. Installation proceeds without error, but the swap file fails to activate.

In general, swap files need to be carefully configured on btrfs. The requirements, as far as I know:

1. linux kernel >5
2. single device btrfs volume
3. copy-on-write disabled on the swap file
4. compression disabled on the swap file
5. no snapshots of the subvolume containing the swap file

On a clean install of Ubuntu 20.04 LTS, I believe 1, 4, and 5 are guaranteed. I think 2 is currently guaranteed because subiquity can't configure a multi-device btrfs volume, and Ubuntu doesn't by default boot from such a volume without some extra tweaking. The main issue is 3.

There is a fix of sorts described in the ubiquity bug, although permissions should also be fixed and the swap file also needs to be initialized:

That fix is probably suitable for the way subiquity currently operates. It might not be appropriate if subiquity allows more complicated btrfs configurations. There's probably a conversation to be had at some point about btrfs support in general.

Related branches

Revision history for this message
ov2k (ov2k) wrote :

To be clear, recreating the swap file with copy-on-write disabled allows the swap file to function as expected and causes systemd to report a properly running system.

Ryan Harper (raharper)
Changed in curtin:
status: New → In Progress
Revision history for this message
Server Team CI bot (server-team-bot) wrote :

This bug is fixed with commit f1bf44f9 to curtin on branch master.
To view that commit see the following URL:

Changed in curtin:
status: In Progress → Fix Committed
ov2k (ov2k)
Changed in curtin:
status: Fix Committed → Fix Released
Changed in subiquity:
status: New → Fix Released
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