Raspberry Pi Pico Tips and Tricks

Friday 26 April 2024

Changing the GRUB boot delay time from the default 30s in Ubuntu 24.04 (SPOILER alert - ZFS)

When installaing a new desktop machine with Ubuntu 24.04 I came across a situation when booting where there was a 30 second delay at the GRUB OS select screen.

This is not something that I was wanting for a new OS, so I looked for a method to sorten or eliminate it.

The normal method is to run `sudo nano /etc/default/grub`. Change the `GRUB_TIMEOUT=30` line to something more appropriate then run `sudo upate-grub` and you're good. However..... my file had  `GRUB_TIMEOUT=0`.

After a few Google searches I discovered that my problem appears to be an artifact of the type of file system I set up (ZFS) when installing the OS.

If GRUB decides that the boot media it is looking at is not writable or that it lacks write support for the filesystem being used it is not able to record that the boot worked so it assumes it failed and generates the boot menu lines. The reported filesystems it doesn't like are

  • btrfs
  • cpiofs
  • newc
  • odc
  • romfs
  • squash4
  • tarfs
  • zfs
  • diskfilter
  • lvm 

There's ZFS <sigh>.

So. I could go back to EXT4, which I really don't want to do because I'm a modern progressive sort of person who wants to be in with the cool kids. So...

I added `GRUB_RECORDFAIL_TIMEOUT=3` to /etc/default/grub (of course you can modify it to your desired value). Save the file and run `sudo update-grub`.

When I ran `sudo update-grub` I recieved a warning that (amongst other things) os-prober will not be executed to detect other bootable partitions. I'm okay with that.

That did the trick.

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