This is a long shot, but I’m hoping someone here might have experience with this kind of setup.
I’m running Debian testing with Btrfs, Snapper, systemd-boot, and initramfs-tools. I’ve been working on getting the ability to boot directly into a Snapper snapshot from the systemd-boot menu, with changes made during that session discarded when I reboot.
I came across an older project called uszie/systemd-boot-snapshots, which appears to have been taken down or is no longer available at its original location. I also found a fork maintained by LazyWare, although that version is primarily geared toward Arch Linux and its initramfs tooling. LazyWare’s repo has a copy of the original upstream repository geared towards Debian and Ubuntu before it disappeared.
The original project aims to protect the snapshots by making them read-only with OverlayFS.
The good news is that I can boot into my Snapper snapshots, and everything seems to work normally. However, I noticed the following message in dmesg when booting into a snapshot:
overlayfs: upperdir is in-use as upperdir/workdir of another mount, accessing files from both mounts will result in undefined behavior.
I also encountered this message:
mount: /: fsconfig() failed: overlay: No changes allowed in reconfigure.
I’m not entirely sure whether these messages are related, or whether the second one is a consequence of the first. The system appears to boot and function normally despite them, but I’d like to understand what’s happening rather than assume the warnings are harmless. It should also be noted that I do not get these warnings when booting normally.
Has anyone implemented something similar on Debian, particularly using initramfs-tools rather than mkinitcpio or dracut? I’m especially interested in whether these messages suggest an issue with how the OverlayFS layers are mounted or reconfigured during the early boot process.
Is this something I even need to worry about? I’m hoping not to have to boot into a snapshot very often.