Merge lp:~lbssousa/lightdm/guest-account-union-mount-skel into lp:lightdm

[Laércio de Sousa]

[UPDATE] Robert, could you please update this merge with a last-minute patch to add a -r (read-only option) for bindfs mounts? Consider also including packages "bindfs" and "linux-image>=3.18 (to ensure overlayfs is available) | aufs-tools" in "Suggests:" field for lightdm package.

This patch proposes an alternative mechanism to customize guest sessions, based on union-mounting /etc/guest-session/skel with guest home directory, rather than just copying over contents from one to the other.

It *may* turn guest logins a bit faster (I've never measured it, however), and it avoids copying large files from /etc/guest-session/skel (e.g. a whole .wine directory) to a limited tmpfs home for guest accounts.

For each guest account created, it wraps /etc/guest-session/skel in a dedicated BindFS mount, so that the account in question will see itself as the owner of that directory's contents. If BindFS is not available, it will fall back directly to current copy over method.

If OverlayFS kernel module is available in the system, use it. However, if only AuFS is available, use it instead. If none of them is available, fall back to current copy over method. If /etc/guest-session/skel is not available, nothing changes: it'll continue copying over from /etc/skel (no union-mounting will be performed in this case).

[Robert Ancell (robert-ancell)]

Looks good!

review: Approve

[Laércio de Sousa (lbssousa)]

Robert, could you please update this merge with a last-minute patch to add a -r (read-only option) for bindfs mounts? Consider also including packages "bindfs" and "linux-image>=3.18 (to ensure overlayfs is available) | aufs-tools" in "Suggests:" field for lightdm package.

[Robert Ancell (robert-ancell)]

Can you do another MP for these changes? It will be easier as you know the exact changes.

=== modified file 'debian/guest-account.sh'
--- debian/guest-account.sh	2015-10-09 19:38:57 +0000
+++ debian/guest-account.sh	2015-10-13 10:34:11 +0000
@@ -69,7 +69,7 @@
 
       # Wrap ${gs_skel} in a BindFS mount, so that
       # guest account will see itself as the owner of ${gs_skel}'s contents.
-      bindfs -M $USER $gs_skel ${PRE_HOME}/lower || {
+      bindfs -r -M $USER $gs_skel ${PRE_HOME}/lower || {
         rm -rf "$PRE_HOME"
         rm -rf "$HOME"
         exit 1