m (update link)
Latest revision as of 22:26, 6 July 2016
It turns out that it is possible to merge down the persistent overlay into the base image, if you have access to another OS installation and sufficient disk space.
- Another OS installation is optional. (See LiveOS image/overlay#Merge overlay into new image.)
- Thanks for demonstrating this technique. --FGrose 01:21, 20 August 2012 (EDT)
- Really. I'd be nervous running that on a loaded system, but I've got to try it now! --Agilmore (talk) 22:11, 2 October 2012 (UTC)
I like that result better than just having to increase the overlay size without bounds.
Tested and working on a Fedora 17 x86_64 Live image installed via livecd-iso-to-disk to a USB stick, all commands as root. You will need disk space sufficient for the uncompressed size of the root filesystem, 4 GB in the case of Fedora 17. I assume only one image and one user on the machine.
Step 1: Get access to read-write base image, note that I got loop2 and loop3 here, YMMV.
mkdir squashfs mount -o loop /run/media/*/LIVE/LiveOS/squashfs.img squashfs/ cp squashfs/LiveOS/ext3fs.img .
Step 2: Set up loopback and device mapper devices for persistent overlay, base device mapper and snapshot.
losetup -f ext3fs.img losetup -f /run/media/*/LIVE/LiveOS/overlay-* echo 0 $(blockdev --getsize /dev/loop2) linear /dev/loop2 0 |dmsetup create orig echo 0 $(blockdev --getsize /dev/mapper/orig) snapshot /dev/mapper/orig /dev/loop3 p 8 | dmsetup create top
Step 3: Stop the snapshot device and merge the snapshot with the base
dmsetup suspend top echo 0 $(blockdev --getsize /dev/loop2) snapshot-merge /dev/loop2 /dev/loop3 p 8 | dmsetup create mergeomatic && dmsetup status mergeomatic
Step 4: Wait for merge to complete. When the status report on mergeomatic reports allocated blocks equal to the metadata blocks, the merge is finished.
Step 5: Remove the merge target.
dmsetup remove mergeomatic
Step 6: Set the top device to no snapshot, and inspect the filesystem for results, if desired.
echo 0 $(blockdev --getsize /dev/loop2) linear /dev/loop2 0 | dmsetup load top dmsetup resume top mkdir root mount /dev/mapper/top root cd root chroot .
Step 7: Clean up.
cd .. umount root dmsetup remove top dmsetup remove orig losetup -d /dev/loop2 losetup -d /dev/loop3 umount squashfs/
Step 8: Copy the root filesystem image back into the squashfs image, you may need -noappend
mkdir LiveOS mv ext3fs.img LiveOS rm /run/media/*/LIVE/LiveOS/squashfs.img mksquashfs LiveOS /run/media/*/LIVE/LiveOS/squashfs.img -keep-as-directory