can't mkdir SNAP_USER_COMMON directory

[Chris J Arges]

In my snap I would like to use the SNAP_USER_COMMON directory in order to persist data across versions. I've observed this both for a snap that executes as a normal user and one that executes as root (daemon).

Test case:
git clone https://gist.github.com/arges/0e31fae032d3d57c5031339e13e81ede

$ make-it-so

mkdir: cannot create directory '/home/arges/snap/make-it-so/common': Permission denied
touch: cannot touch '/home/arges/snap/make-it-so/common/canttouchit': No such file or directory

$ dmesg | tail

[14090.089664] audit: type=1400 audit(1470677502.367:131): apparmor="DENIED" operation="mkdir" profile="snap.make-it-so.make-it-so" name="/home/arges/snap/make-it-so/common/" pid=4061 comm="mkdir" requested_mask="c" denied_mask="c" fsuid=1000 ouid=1000

[Jamie Strandboge (jdstrand)]

Note that snapd should be creating this directory for you and you shouldn't have to create it yourself.

[Bruno Nova (brunonova)]

Yes, the problem is probably that the launcher script in /snap/bin/ doesn't create that directory.
Maybe the description of the bug should be changed?

The launcher scripts needs to include these lines, I think:
if [ ! -d "$SNAP_USER_COMMON" ]; then
   mkdir -p "$SNAP_USER_COMMON"
fi

[Eldar Khayrullin (eldar)]

To brunonova, your methode shows perm denied:
mkdir: cannot create directory '/home/user/snap/my-snap/common': Permission denied

[Eldar Khayrullin (eldar)]

The temporary solve:
$ snap run my-snap
This cmd create COMMON directory (Needs to ignore errors of prev cmd).

[Bruno Nova (brunonova)]

@Eldar, I was talking about the launcher scripts created in "/snap/bin/" by snapd itself during "snap install", not about scripts bundled with the snap.

As users, we can create the "common" directory manually.
But, as developers/packagers, we can't do much.

[Eldar Khayrullin (eldar)]

@Bruno, Ok, I'm agree with you.

[Kyle Fazzari (kyrofa)]

Note that this issue will be resolved as soon as `snap run` is used to launch apps (it's what has the logic to create this directory). That will be released soon!

[Michael Vogt (mvo)]

We use `snap run` now and this will create the dir with the right permissions automatically