initramfs-tools looking for non-existant swap partition

[Snowhog]

I have btrfs as the filesystem on my 18.04 VirtualBox VM. When I dist-upgrade, I see this:

Processing triggers for initramfs-tools (0.130ubuntu2) ...
update-initramfs: Generating /boot/initrd.img-4.14.0-15-generic
W: initramfs-tools configuration sets RESUME=UUID=11d6acf2-91b7-4717-b6f9-4a949c5a6f96
W: but no matching swap device is available.

When I set up the VM I opted not to have a swap, as I read that btrfs doesn't/won't use it even if it is present. So were is the RESUME=UUID value coming from, and why is initramfs-tools looking for a swap that doesn't exist? Just curious.

[oshunluvr]

Is there a /etc/initramfs-tools/conf.d/resume file? If so, try deleting (moving) it.

[oshunluvr]

To the other part - it's not that btrfs won't use swap. It's really not up to any file system to decide if your system uses swap or not. It is not recommended to use a swap file on a btrfs file system as the COW functionality may cause corruption of the swap file. The default installer now-a-days will create a swap file if a swap partition isn't present at installation, rather than creating a partition like it used to.

The correct advice should have been to create a swap partition prior to or during installation if using btrfs as the installation file system and the use of swap is desired.

Frankly, IMO this change is potentially damaging to anyone unaware of the issue and should be considered a bug.

[GreyGeek]

Does
blkid
show that UUID?

[oshunluvr]

And there you go: https://bugs.launchpad.net/ubuntu/+s...y/+bug/1651250

[oshunluvr]

I just checked mine here. I have a UUID in /etc/initramfs-tools/conf.d/resume and it is indeed one of my swap partitions. Interestingly, I've never hibernated (it's a desktop) that I know of. I have 2 swap partitions because if you have more than one and give them equal priority, they supposedly act as RAID0 and share the load. Although even with 2 swap partitions on my two Samsung 840Pro SSD's swapping out is still slow as all-get-out. I wonder is resume would even work because the file only points to one of the two swap partitions.

[Snowhog]

No resume file in /etc/initramfs-tools/conf.d. Interestingly, the warning didn't appear this time when I ran full-upgrade (sudo apt full-upgrade) after having updated the package cache.