Running Ubuntu 18.04, I changed from a swap partition to a swap file.
swapon -s (summary) and free show the swapfile with the new size. /etc/fstab was changed, permission on the swapfile changed and the swap partition was deleted. When there are updates (apt-get update and upgrade), I get this error:
Setting up amd64-microcode (3.20180524.1~ubuntu0.18.04.2) ... update-initramfs: deferring update (trigger activated) amd64-microcode: microcode will be updated at next boot Processing triggers for libc-bin (2.27-3ubuntu1) ... Processing triggers for initramfs-tools (0.130ubuntu3.1) ... update-initramfs: Generating /boot/initrd.img-4.15.0-29-generic W: initramfs-tools configuration sets RESUME=UUID=c5a2c6f4-b67c-4d95-bc23-8333ed6c0f11 W: but no matching swap device is available.
The UUID listed there is for the old swap partition. I didn't think a swap file has a UUID, but I am not sure about that. Everything else seems to work fine. How should I proceed to troubleshoot and fix this?
Best Answer
That line is in /etc/initramfs-tools/conf.d/resume so try deleting it.
The file in question, /etc/initramfs-tools/conf.d/resume, hasn't even existed in an Ubuntu LTS release since 14.04. Deleting the one line it contained on an 18.04 system will never cause a problem. This is a great example of why a reinstall is preferable to an upgrade, sometimes old things get left which can later cause problems.
As for those who think blkid will produce anything at all for a swapfile, you are wrong, and the answer which suggest using blkid is non-responsive to the stated problem. Reread the question, there is no longer a swap partition.
As a comment suggested, a UUID for the swapfile may be produced with swaplabel, but it is left as an exercise for the reader to see if using that swapfile UUID in a configuration file which is no longer part of the Ubuntu system will actually fix anything, or just result in another UUID lookup failure.