I installed ubuntu-clock-app. Once I had to emergency turn off my computer (hard reset), this application has stopped working.
datafile4@datafile4-K53SD:~$ sudo snap remove ubuntu-clock-app
error: can't remove "ubuntu-clock-app": cannot find mounted snap "ubuntu-clock-app" at revision 5
At the same time
datafile4@datafile4-K53SD:~$ sudo snap install ubuntu-clock-app
error: can't install "ubuntu-clock-app": snap "ubuntu-clock-app" already installed
snap changes result:
Status Spawn Ready Summary
Done 2016-05-01T07:51:19Z 2016-05-01T07:51:20Z Make snap "ubuntu-clock-app" unavailable to the system
Undone 2016-05-01T07:51:19Z 2016-05-01T07:51:21Z Remove security profile for snap "ubuntu-clock-app"
Done 2016-05-01T07:51:19Z 2016-05-01T07:51:20Z Remove data for snap "ubuntu-clock-app"
Error 2016-05-01T07:51:19Z 2016-05-01T07:51:20Z Remove snap "ubuntu-clock-app" from the system
Hold 2016-05-01T07:51:19Z 2016-05-01T07:51:20Z Discard interface connections for snap "ubuntu-clock-app"
......................................................................
Remove snap "ubuntu-clock-app" from the system
2016-05-01T11:51:20+04:00 ERROR remove /snap/ubuntu-clock-app/5/bin/clock: read-only file system
Best Answer
One way out of this, if you don't care to lose the data associated with the snaps, is to run Zyga's reset state script.
Also, please make sure you're on snapd 2.0.3, which was released to xenial last week; that way you shouldn't get into this state again.