Problem: In Ubuntu 24.04 you see available updates, but the update fails with “cannot refresh snap-store”.
This is a known logical problem due to the half-baked integration of the canonical snap store next to apt in ubuntu. The snap store is a snap package itself, so if you start it to update your snap packages, it tries to update itself, which of course is not possible.
Solution: Update snap-store from the terminal.
First, kill the running snap store instance with:
sudo killall snap-store
Then update your snap store with:
sudo snap refresh snap-store
This may work at first try. But sometimes snap has already started some applications, then you probably get a message like:
error: cannot refresh "snap-store": snap "snap-store" has running apps (ubuntu-software), pids: 4450
This just means that you have to stop some more programs blocking the update. Terminate them by their pid, that you can see in the previous output, in this case its 4450:
kill 4450
Do that for every pid in the list. If some pids won’t terminate, try with the parameter -9 (SIGKILL), in this case it would be: kill -9 4450
Try to update snap-store again, it should be working now:
sudo snap refresh snap-store
snap-store (stable/ubuntu-24.04) 0+git.ec3fa65 from Canonical✓ refreshed