Comment 3 for bug 712689

Note that you shouldn't use fsfreeze on a filesystem where there is lots of IO - notably, rootfs (/).

If you do so, all programs write-accessing it will be "frozen" as well, which could explain your system freeze.

Try doing it on a filesystem which is not the main one, like /boot, or similar (i.e. /var/lib/mysql, if it's a separate partition).

If "sudo fsfreeze --freeze / ; sudo fsfreeze --unfreeze /" is expected to freeze the system hard is a different question - perhaps someone should ask on a linux-fsdevel or similar mailing list.

http://vger.kernel.org/vger-lists.html#linux-fsdevel