I'm trying to use zerofree, which seems to be the answer for this: How to reduce VM size?
I have successfully umounted /dev/sda1, and zerofree worked fine, releasing ~37gb.
But I can't seem to umount or remount as read only /dev/mapper/mypc-root, it says:
umount: / is busy
mount: / is busy
The commands used were:
$ umount /dev/mapper/mypc-root $ mount -no remount,ro -t ext2 /dev/mapper/mypc-root /
I'm in single user mode, entered it with 'init 1'.
The guest SO is Ubuntu 12, with encrypted LVM and home.