Comment 3 for bug 1931027

I give you a longer description to explain the situation.

>>> We have many different types of 20.04 isos.... which one do you mean? <<<
All the desktop-isos of Ubuntu (ubuntu-20.04.1.0-desktop-amd64.iso for example, older and newer too) are affected.

>>> What are you trying to achieve? <<<
At the moment i use ubuntu-18.04.1-desktop-amd64.iso, running from USB to create a customized live-system without re-creation of the whole squashfs.

Booted from USB with "showmounts", additional installed initramfs-tools_0.130ubuntu3.6-packages (all, core, bin) and the "dirty fix" of the casper-script from https://bugs.launchpad.net/ubuntu/+source/casper/+bug/1520575 i snapshot all my changes in cpio-format.

The snapshot file must be stored as casper-snapshot.cpio.gz directly under /cdrom in the running live -system (filesystem remounted with -rw), on the USB stick it is then directly in the root of the fs. Now you can boot the live-system with "showmounts persistent" and you have a customized system without re-creation of the whole filesystem.squashfs file. The "dirty fix" from +bug/1520575 makes the deal so the snapshot file will mount properly as the upper layer. Without the fix you will end in a busy box.

>>> Are you trying to make casper-snapshot to work? or showmounts to work? <<<
Now with 20.04 i can not snapshot changes. The /cow folder does not exist when booting with "showmounts", nowhere in the running livesystem you can identify additional / deleted / changed files or folders in a separate location like /cow/upper to snapshot it.

Yes, you can create /cow and /cow/upper manually after booting. But when you create a new file, nothing happens there. In 18.04 (and older) you can see the changes at <original location> and under /cow/upper/<original location>.

My knowledge is not sufficent enough to identify the root cause. Is it a problem with newer 5.x kernels or with newer casper-scripts?