I have the unique pleasure of waiting as /usr is copied back to my Ubuntu SSD after offloading it to a sea of spinning rust to save some space. Surprise surprise Ubuntu keeps almost everything in /usr these days and it didnt boot :l but hey, at least BusyBox in initramfs has my back for times like these. Can i mount a specific ext4 directory with options? the issue seems to be my attempt at using a bind mount fails while running from the ramdisk, for whatever reason it wont mount my large data drive on /data
Interestingly, when I added the bind mount to /usr the init environment failed when trying to set up the actual root fs because it was trying to bind mount from the init ramdisk filesystem paths into the new root path. im sure I could cloodge together a script to patch things up in the initrd but my days of straying from a sane upgrade path on Ubuntu are over (now I just do that on nixos because I don't know what I'm doing)
I would think you could put /usr on a separate disk just fine, as long as it was available to mount at boot time.
How small is your SSD that you're trying weird stuff to save space? Even in the tens of gigs should be enough to run Ubuntu. I just checked two full desktop systems, and they are 32 and 24 GB used for the root partition.
I'm just irresponsible with installing software on my desktop machine. It's a 50g partition but I use it for music, software development, and some games (looking at you flightgear) which eventually add up. I've been slowly moving pieces of the setup onto a 3tb rust gyroscope with mostly success. Luckily this blunder was recoverable and I'm back to where I was before
Maybe using these instructions, you can still offload /usr to a mechanical drive.
Just out of curiosity, how large is your /usr directory? Mine is only 30GiB (arch Linux, kde plasma with all apps + hyprland), which only takes up 17GiB on my disk due to btrfs compression (zstd level 15).
Ohh I like the sound of that compression ratio, I'll have to look into it. I'm just using ext4, plus I should repartition the whole disk I'm throwing away another 50Gb keeping my home partition on the SSD...
My /usr is 35Gb but I'm squeezing Ubuntu into a 50Gb partition and between docker, snapd, postgres, apt, and Minecraft it's hitting 100% weekly.
Im pretty sure it would be fine if i was trying to dedicate a whole partition to /usr, maybe that's the right answer after all