Cannot remove snap package ubuntu 20.10

[Adams Jensen]

Hi
after upgrading to ubuntu 20.10 snap packages are no longer removed.
bug reported from snapcraft.io
https://forum.snapcraft.io/t/cant-remove-uninstall-snap-packages/12810/4

snap 2.47.1+20.10.1
snapd 2.47.1+20.10.1
series 16
ubuntu 20.10
kernel 5.8.0-25-generic

andrei@X570-GAMING-X:~$ sudo snap remove opera
[sudo] пароль для andrei:
ошибка: cannot perform the following tasks:
- Save data of snap "opera" in automatic snapshot set #34 (user: lookup userid 1001: no such file or directory)

[Ian Johnson (anonymouse67)]

Hi, what does:

```
id 1001
```

return on this system?

[Luis Alberto Pabón (copong)]

I'm seeing the same problem after a clean install of 20.10 over a pre-existing home folder.

~ sudo snap remove slack
error: cannot perform the following tasks:
- Save data of snap "slack" in automatic snapshot set #4 (user: lookup userid 1001: no such file or directory)

~ id 1001
id: ‘1001’: no such user: No such file or directory

There used to be a user 1001 in my system before I reinstalled (just not mine, some other I use to try out other desktop environments).

[Luis Alberto Pabón (copong)]

After adding a second user...

~ sudo snap remove slack
error: cannot perform the following tasks:
- Save data of snap "slack" in automatic snapshot set #5 (user: lookup userid 1002: no such file or directory)

I did have a third user for testing out other things.

[Luis Alberto Pabón (copong)]

After adding some random third user, snap removal works again.

[Zygmunt Krynicki (zyga)]

This is caused by a bug in the snapshot code, which enumerates users by their HOME entries. We should handle this case better.

[Zygmunt Krynicki (zyga)]

I was curious where we do this so I went looking and this is the start of the problem:

https://github.com/snapcore/snapd/blob/7ff96a40a7a7a7779db250b087cec9b183540130/overlord/snapshotstate/backend/helpers.go#L145

In absence of other information, we snapshot the state for all the users this way.

[Paweł Stołowski (stolowski)]

I'll work on a fix; as workaround it is also possible to use 'snap remove --purge <snap>' (which of course skips snapshot creation).

[Paweł Stołowski (stolowski)]

I investigated and reproduced this with:

$ snap install hello-world
$ mkdir /home/fakeuser/snap
$ chown -R 1090:1088 /home/fakeuser (use uid:gid that are not used on the system).
$ snap remove hello-world

The problem is only affecting groovy and it appears to be fixed with https://github.com/snapcore/snapd/pull/9041/ (which landed on Sep 28th but hasn't been released in stable yet; the fix is included in snapd from edge).