On 19/11/2020 17.19, Holger Jakob wrote: Hi -
I ran into an issue with the script /usr/lib/linux-boot-probes/50mounted-tests (os-prober package) mounting an already mounted btrfs volume and effectively corrupting that volume. This occurred automatically during a "zypper update" on a Leap 15.2 system. /var/log/message outputs indicate the volume was actually mounted. At that time the volume was already in used by a XEN VM. The volume is part of a LVM Volume Group and lvdisplay indicated the volume was already in use.
1. Why is this script needed when dracut/grub is updating the initrd files and why does it touch (rw mount) volumes unrelated to the boot process?
2. Why did the btrfs partition not rejecting any further mount attempts (as it was already opened elsewhere)?
3. In order to prevent this from happening in the future is it safe to remove "os-prober" or can the script be modified to leave certain volumes untouched?
You can certainly disable os-prober. Edit "/etc/default/grub":
GRUB_DISABLE_OS_PROBER="true"
Thanks for this advice. I have made the change and hope it will just work. If this is really just for detection of foreign OSs I am not worried about it at all.
Mounted something twice should not corrupt it. os-prober mounts everything to find out if that partition is bootable, and then add it to the boot menu.
I think this only applies for mounts with the same kernel. VMs with independent kernels could really mess up things. Since I am still in the middle of "disaster recovery" I cannot confirm my theory but logs seems to indicate the host was actually writing to the btrfs volume during the os-probe run. And, there is an old CentOS ticket describing a very similar situation: https://bugs.centos.org/view.php?id=10918 I think I will reach out to the os-prober maintainers to see what they can do. The latest version 1.77 does not list any btrfs related changed relative to 1.76 used in Leap 15.2. Holger --