Content provider interfaces introduced to snaps aren't correctly set up

[Marco Trevisan (Treviño)]

This happened in the telegram-snap (and others that I don't manage, so I can't define a list or detailed changes), but it happened the first time when I introduced the usage of the `desktop` plug, and now again once adding the content interfaces provided by gtk-common-themes.

Here's what happened:
 1) telegram-desktop was providing fonts and etc
 2) Added the `desktop` plug
 3) Most of users who have auto-refreshed the snap have an
    empty /usr/share/fonts mount point
 3) I started using the gtk-common-themes interface to provide resources:
    https://github.com/3v1n0/telegram-snap/commit/4f4c3ce8fbce1a8d36
 4) Fresh install works fine
 5) After auto-refreshing the snap in some machines (here too) nothing is
    mounted in my $SNAP/usr/share/

All this is generally fixed by uninstalling and reinstalling the snap. Next refreshes are fine.

This has been already briefly discussed at the previous engineering sprint.

[Zygmunt Krynicki (zyga)]

I will attempt to reproduce this but you could provide some additional details that would help:

- the before and after revision numbers (so that I can reproduce this precisely)
- the content of /run/snapd/ns/snap.telegram-desktop.fstab
- the content of /var/lib/snapd/mount/snap.telegram-desktop.fstab
- the output of:
  run: $ nsenter -m/run/snapd/ns/telegram-desktop.mnt
  in the new shell run: cat /proc/self/mountinfo

[Marco Trevisan (Treviño) (3v1n0)]

Current stable (233) is still not using content interface, while edge (248 right now) does use content interface.

marco@tricky:~:✗ $ cat /run/snapd/ns/snap.telegram-desktop.fstab
/var/lib/snapd/hostfs/usr/local/share/fonts /usr/local/share/fonts none bind,ro 0 0
/var/lib/snapd/hostfs/usr/share/fonts /usr/share/fonts none bind,ro 0 0
/var/lib/snapd/hostfs/var/cache/fontconfig /var/cache/fontconfig none bind,ro 0 0

marco@tricky:~:✓ $ cat /var/lib/snapd/mount/snap.telegram-desktop.fstab
/snap/gtk-common-themes/319/share/icons/Adwaita /snap/telegram-desktop/248/usr/share/icons/Adwaita none bind,ro 0 0
/snap/gtk-common-themes/319/share/icons/hicolor /snap/telegram-desktop/248/usr/share/icons/hicolor none bind,ro 0 0
/snap/gtk-common-themes/319/share/icons/HighContrast /snap/telegram-desktop/248/usr/share/icons/HighContrast none bind,ro 0 0
/snap/gtk-common-themes/319/share/icons/Humanity /snap/telegram-desktop/248/usr/share/icons/Humanity none bind,ro 0 0
/snap/gtk-common-themes/319/share/icons/Humanity-Dark /snap/telegram-desktop/248/usr/share/icons/Humanity-Dark none bind,ro 0 0
/snap/gtk-common-themes/319/share/icons/ubuntu-mono-dark /snap/telegram-desktop/248/usr/share/icons/ubuntu-mono-dark none bind,ro 0 0
/snap/gtk-common-themes/319/share/icons/ubuntu-mono-light /snap/telegram-desktop/248/usr/share/icons/ubuntu-mono-light none bind,ro 0 0
/snap/gtk-common-themes/319/share/icons/DMZ-Black /snap/telegram-desktop/248/usr/share/icons/DMZ-Black none bind,ro 0 0
/snap/gtk-common-themes/319/share/icons/DMZ-White /snap/telegram-desktop/248/usr/share/icons/DMZ-White none bind,ro 0 0
/snap/gtk-common-themes/319/share/icons/Solus /snap/telegram-desktop/248/usr/share/icons/Solus none bind,ro 0 0
/snap/gtk-common-themes/319/share/icons/communitheme /snap/telegram-desktop/248/usr/share/icons/communitheme none bind,ro 0 0
/snap/gtk-common-themes/319/share/icons/Suru /snap/telegram-desktop/248/usr/share/icons/Suru none bind,ro 0 0
/var/lib/snapd/hostfs/usr/share/fonts /usr/share/fonts none bind,ro 0 0
/var/lib/snapd/hostfs/usr/local/share/fonts /usr/local/share/fonts none bind,ro 0 0
/var/lib/snapd/hostfs/var/cache/fontconfig /var/cache/fontconfig none bind,ro 0 0
/snap/gtk-common-themes/319/share/sounds/communitheme /snap/telegram-desktop/248/usr/share/sounds/communitheme none bind,ro 0 0
/snap/gtk-common-themes/319/share/themes/Adwaita /snap/telegram-desktop/248/usr/share/themes/Adwaita none bind,ro 0 0
/snap/gtk-common-themes/319/share/themes/Adwaita-dark /snap/telegram-desktop/248/usr/share/themes/Adwaita-dark none bind,ro 0 0
/snap/gtk-common-themes/319/share/themes/HighContrast /snap/telegram-desktop/248/usr/share/themes/HighContrast none bind,ro 0 0
/snap/gtk-common-themes/319/share/themes/Ambiance /snap/telegram-desktop/248/usr/share/themes/Ambiance none bind,ro 0 0
/snap/gtk-common-themes/319/share/themes/Radiance /snap/telegram-desktop/248/usr/share/themes/Radiance none bind,ro 0 0
/snap/gtk-common-themes/319/share/themes/EvoPop /snap/telegram-desktop/248/usr/share/themes/EvoPop none bind,ro 0 0
/snap/gtk-common-themes/319/share/themes/EvoPop-Azure /snap/telegram-desktop/248/usr/share/themes/EvoPop-Azure none bind,ro 0 0
/snap/gtk-common-themes...

[Zygmunt Krynicki (zyga)]

Thank you for the data, it is very interesting. I need to check some things now.

[Marco Trevisan (Treviño) (3v1n0)]

Looks like this issue is still happening. Even for new installs (willcooke provided the following data).

Connection is fine: https://paste.ubuntu.com/p/3fV6NRwvmb/

snap run --shell telegram-desktop -c 'find $SNAP/usr/share/themes'
find: '/snap/telegram-desktop/281/usr/share/themes': No such file or directory

That happens on a broken system, while when the mount happened properly, theme files are of course listed.

[Will Cooke (willcooke)]

Logs as requested.

snap changes:
$ snap changes
ID Status Spawn Ready Summary
385 Done today at 12:03 BST today at 12:04 BST Install "telegram-desktop" snap from "edge" channel

snap changes: https://paste.ubuntu.com/p/rmTcSFZGG9/
journal: https://paste.ubuntu.com/p/Zz3W8dRPXF/
fstab: https://paste.ubuntu.com/p/7Fdr9nfJYm/

/run/snapd/ns/snap.telegram-desktop.fstab: https://paste.ubuntu.com/p/nVnJDVdjgS/

[Will Cooke (willcooke)]

$ ls -l /snap/gtk-common-themes/701/share/icons/Suru
lrwxrwxrwx 1 root root 12 Sep 11 16:56 /snap/gtk-common-themes/701/share/icons/Suru -> communitheme

[Marco Trevisan (Treviño) (3v1n0)]

Ah, missing thing from the irc log:

$ sudo /usr/lib/snapd/snap-update-ns telegram-desktop
2018/09/27 13:08:53.110962 main.go:192: cannot change mount namespace of snap "telegram-desktop" according to change mount (/snap/gtk-common-themes/701/share/icons/Suru /snap/telegram-desktop/281/usr/share/icons/Suru none bind,ro 0 0): cannot use "/snap/gtk-common-themes/701/share/icons/Suru" as bind-mount source: not a directory

This is probably the issue, as per:

$ ls -l /snap/gtk-common-themes/701/share/icons/Suru
lrwxrwxrwx 1 root root 12 Sep 11 16:56 /snap/gtk-common-themes/701/share/icons/Suru -> communitheme

[Marco Trevisan (Treviño) (3v1n0)]

https://github.com/snapcrafters/gtk-common-themes/issues/16

[Zygmunt Krynicki (zyga)]

I believe the snapd side of this issue is fixed now.