False-positive error "/cow format specified as 'overlay' and no support found"

[Daniel J Blueman]

When booting a kernel with overlayfs build-in, ie not as a module, booting incorrectly errors out with:
/cow format specified as 'overlay' and no support found

This turns out to be a false-positive since, in scripts/casper we have:

modprobe "${MP_QUIET}" -b overlay || panic "/cow format specified as 'overlay' and no support found"

This was added previously when there was an out-of-tree overlay filesystem, now deprecated by the in-tree overlayfs.

The correct fix is to change the line to:
modprobe "${MP_QUIET}" -b overlay

If there is no overlayfs support, the later 'mount' command will fail.

ProblemType: Bug
DistroRelease: Ubuntu 23.10
Package: casper (not installed)
ProcVersionSignature: Ubuntu 6.5.0-21.21-generic 6.5.8
Uname: Linux 6.5.0-21-generic x86_64
ApportVersion: 2.27.0-0ubuntu5
Architecture: amd64
CasperMD5CheckResult: pass
CurrentDesktop: ubuntu:GNOME
Date: Mon Feb 26 15:59:14 2024
InstallationDate: Installed on 2022-09-09 (535 days ago)
InstallationMedia: Ubuntu 22.10 "Kinetic Kudu" - Alpha amd64 (20220829)
SourcePackage: casper
UpgradeStatus: Upgraded to mantic on 2023-10-14 (135 days ago)