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| 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.
| | Previous content for this page is now at the Fedora Project wiki, [[fedora:Talk:LiveOS image]]. --[[User:FGrose|FGrose]] 22:15, 21 August 2012 (EDT) |
| I like that result better than just having to increase the overlay size without bounds.
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| 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.
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| Step 1: Get access to read-write base image, note that I got loop2 and loop3 here, YMMV.
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| <nowiki>mkdir squashfs
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| mount -o loop /run/media/*/LIVE/LiveOS/squashfs.img squashfs/
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| cp squashfs/LiveOS/ext3fs.img .</nowiki>
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| Step 2: Set up loopback and device mapper devices for persistent overlay, base device mapper and snapshot.
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| <nowiki>losetup -f ext3fs.img
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| losetup -f /run/media/*/LIVE/LiveOS/overlay-*
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| echo 0 $(blockdev --getsize /dev/loop2) linear /dev/loop2 0 |dmsetup create orig
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| echo 0 $(blockdev --getsize /dev/mapper/orig) snapshot /dev/mapper/orig /dev/loop3 p 8 | dmsetup create top</nowiki>
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| Step 3: Stop the snapshot device and merge the snapshot with the base
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| <nowiki>dmsetup suspend top
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| echo 0 $(blockdev --getsize /dev/loop2) snapshot-merge /dev/loop2 /dev/loop3 p 8 | dmsetup create mergeomatic && dmsetup status mergeomatic</nowiki>
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| 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.
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| dmsetup status
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| Step 5: Remove the merge target.
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| dmsetup remove mergeomatic
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| Step 6: Set the top device to no snapshot, and inspect the filesystem for results, if desired.
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| <nowiki>echo 0 $(blockdev --getsize /dev/loop2) linear /dev/loop2 0 | dmsetup load top
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| dmsetup resume top
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| mkdir root
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| mount /dev/mapper/top root
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| cd root
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| chroot .</nowiki>
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| Step 7: Clean up.
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| <nowiki>cd ..
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| umount root
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| dmsetup remove top
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| dmsetup remove orig
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| losetup -d /dev/loop2
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| losetup -d /dev/loop3
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| umount squashfs/</nowiki>
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| Step 8: Copy the root filesystem image back into the squashfs image, you may need -noappend
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| <nowiki>mkdir LiveOS
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| mv ext3fs.img LiveOS
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| rm /run/media/*/LIVE/LiveOS/squashfs.img
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| mksquashfs LiveOS /run/media/*/LIVE/LiveOS/squashfs.img -keep-as-directory</nowiki>
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| Sources: <br>
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| *http://smorgasbord.gavagai.nl/2010/03/online-merging-of-cow-volumes-with-dm-snapshot <br>
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| *http://www.kernel.org/doc/Documentation/device-mapper/snapshot.txt<br>
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| *http://linuxgazette.net/114/kapil.html<br>
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| --[[User:Andrew Gilmore|Andrew Gilmore]] | |