Comment 2 for bug 1507796

I just tried Ubunte MATE 15.10-beta2. Snapshot persistence does not work under it for the same reasons that it does not work under 15.04. 15.10-beta2 introduces an additional problem: using a boot argument of "persistent" causes the system to not successfully initialize.

Without a boot argument of "persistent", the "Try Ubuntu MATE without installing" item of the GRUB menu works correctly. The result is a MATE desktop with an open window with the title "Welcome to Ubuntu MATE".

With a boot argument of "persistent", the result is an interactive shell on the console that starts with the lines:

  BusyBox v1.22.1 (Ubuntu 1:1.22.0-15ubuntu1) built-in shell (ash)
  Enter 'help' for a list of built-in commands.

  (initramfs)

At that time, the last few lines of the casper.log file were

  /scripts/casper-bottom/43disable_updateinitramfs: line 44: can't create /root/
usr/sbin/update-initramfs: nonexistent directory
  chmod: /root/usr/sbin/update-initramfs: No such file or directory
  chroot: can't execute 'chown': No such file or directory
  chroot: can't execute 'debconf-copydb': No such file or directory

Entering the command 'exit' in that shell results in lines written to the console which indicate that a panic has occurred.

With boot arguments of "persistent debug" the casper.log file is larger. The contents of that casper.log file indicate that the mountroot() function of /scripts/casper ran at least up to the line preceeding

  kill "$tailpid"

Booting without "persistent" and modifying /etc/casper.conf to make it appear as if /script/casper ran and found a snapshot file, causes /sbin/casper-snapshot to run during shutdown. At that time /cow is an empty directory, as it is with Ubuntu MATE 15.04.