Difference between revisions of "Talk:LiveOS image"

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(Replaced content with "Previous content for this page is now at the Fedora Project wiki, fedora:Talk:LiveOS image. --~~~~")
 
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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.
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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)
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: Another OS installation is optional. (See [[LiveOS image#Image recompression and overlay refreshment]].) 
 
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: Thanks for demonstrating this technique.  --[[User:FGrose|FGrose]] 01:21, 20 August 2012 (EDT)
 
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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]]
 
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: I think we should move most of this Fedora content to the Fedoraproject wiki, probably as a subpage to [[fedora:How to create and use Live USB]]. --[[User:FGrose|FGrose]] 01:21, 20 August 2012 (EDT)
 

Latest revision as of 21:15, 21 August 2012

Previous content for this page is now at the Fedora Project wiki, fedora:Talk:LiveOS image. --FGrose 22:15, 21 August 2012 (EDT)

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