Many LiveCD distributions (for example Lubuntu 12.10 I use) allow making changes, for example updating timezone, logging in to Google Chrome, updating and installing additional packages such as OpenVPN. They do that by overlaying read-write filesystem, in my case RAM-based tmpfs (or ramdisk, or ramfs, or USB pendrive), over CD-ROM based filesystem, in my case system image via squashfs but might be iso9660 or udf directly, using some union filesystem, in my case overlayfs (or unionfs, or aufs).

I'd like to make copy of changes (e.g. using dd) and only changes of an existing running LiveCD (e.g. Lubuntu 12.10) and I don't want to make copy of whole '/' mountpoint, including both changes and original CD-ROM. How can I find device or mountpoint which I can point e.g. dd to?

mount shows the following (excerpt):

/cow on / type overlayfs (rw)
tmpfs on /run type tmpfs (rw,noexec,nosuid,size=10%,mode=0755)
/dev/sr0 on /cdrom type iso9660 (ro,noatime)
/dev/loop0 on /rofs type squashfs (ro,noatime)
tmpfs on /tmp type tmpfs (rw,nosuid,nodev)
none on /run/lock type tmpfs (rw,noexec,nosuid,nodev,size=5242880)
none on /run/shm type tmpfs (rw,nosuid,nodev)
none on /run/user type tmpfs (rw,noexec,nosuid,nodev,size=104857600,mode=0755)

Original question: Persisting changes on Lubuntu 12.10 run from LiveCD on Ask Ubuntu (no answers as of posting this one).

  • Look at the mount output, the CD and some RAM are mounted as unionfs. Instead of the RAM you could use a USB stick.
    – ott--
    Commented Jun 13, 2013 at 13:14
  • But from the above (just added) output, which is filesystem / device that is overlaid over squashfs? Commented Jun 13, 2013 at 19:19
  • How about creating a bootable usb stick with unetbookin - unetbootin.sourceforge.net - and using the "persist data" option?
    – user34720
    Commented Jun 14, 2013 at 2:45
  • The problem is not creating or selecting LiveCD / LiveUSB (thanks for the advice, @nwildner) with persistent changes (saved on hard disk or USB pendrive), the problem is backup of data from LiveCD I am using. Commented Jun 14, 2013 at 6:44
  • Ah, ok. I got the idea now. It is about making a backup of the pendrive, not a backup of what is modified with the live distro booted up. Well, if you have 2 equal pendrives(manufacturer and model) a dd could be enough to make a backup(dd if=/dev/sdc of=/dev/sdd bs=10M conv=notrunc). I'm still thinking if there is a way to make a filesystem level backup of it...
    – user34720
    Commented Jun 14, 2013 at 10:47

1 Answer 1


On Ubuntu sticks, look for a file called casper-rw while the stick is not booted. That file should contain the changes.

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