Snapshots and rollback

Every Immos update keeps the previous system image. If an update ever causes trouble, you can return to the version that worked — usually in under a minute.

Overview

Because Immos runs from a read-only image, each installed version is a distinct, self-contained snapshot. Updating does not modify your running system in place — it writes a new image into the free slot and switches to it on the next reboot. The old image stays on disk, so you can switch back at any time.

Your files are separate

Rolling back only changes the system image. Your home folder, documents and app data are never touched.

Listing what is installed

immos-update status shows which version is in which slot, which one you booted, and whether a staged update is waiting:

immos ~$

$ immos-update status
● 0.2.0   booted    slot 1
  0.1.0             slot 2
  boot entries: immos_0.2.0.efi (blessed), immos_0.1.0.efi

Rolling back on purpose

To boot the previous image, tell the bootloader to prefer it and reboot:

immos ~$

$ immos-update rollback
→ Next boot: 0.1.0
  Reboot to apply.
$ systemctl reboot

You can also hold Space during startup to bring up the boot menu and pick any image on disk for a single boot, without changing the default.

Rolling back automatically

You do not have to be there for this. When an update is installed, its boot entry is given three attempts. Each boot decrements the counter; a boot that reaches a working graphical desktop marks the entry permanently good and stops the counting.

If three attempts pass without the system coming up properly, the bootloader stops offering that entry and starts the previous version instead — whose image is still sitting in the other slot, untouched. No server, no agent, no recovery media.

That means the interesting failure cases handle themselves:

What went wrong	What happens
New image will not boot at all	Three failed attempts, then the previous version boots
New image boots but the desktop never starts	Counted as a failed boot; same rollback
Power lost during the update	The new slot is unfinished and never marked valid; the running version is unaffected
Download corrupted or unsigned	Rejected before anything is written

Rolling forward again

Rolling back is not destructive either. The newer image is still in its slot; if you rolled back to investigate something and want to return, boot the newer version from the boot menu, or run immos-update rollback again to swap the default back.

What a rollback does not undo

Rollback moves the system image, and only the system image. It does not revert:

your files, settings or application data
Flatpak applications and their updates
changes you made under /etc

If a system update changed a vendor default and you want that reverted too, rolling back the image restores the vendor version of every file you have not personally edited. Files you have edited keep your version — see editing /etc.