W: Couldn't identify type of root file system '/dev/pve/rootu/dev/pve/root' for fsck hook

jacobrale

Member
Apr 29, 2023
5
0
6
I get text in the subject as a warning in /var/log/term.log when I run my PVE updates. I gather it's not a problem, because everything works fine. Also, there is no '/dev/pve/rootu/dev/pve/root'. Thoughts? I don't want to ignore a warning that might actually be tried to tell me something significant!
 
Welcome, @jacobrale .

I would search for this string. E.g.:

grep -r rootu /etc
and maybe in and below /boot as well:
grep -r rootu /boot
 
Last edited:
Thanks! fstab has: "/etc/fstab:/dev/pve/rootu/dev/pve/root / ext4 errors=remount-ro 0 1" that is it. What dev is "dev/pve/rootu/dev/pve/root"? There is nothing there? Is this some sort of zfs thing I don't get? Does not seem right. When I run "zfs list -o name,mounted,mountpoint" i get:

NAME MOUNTED MOUNTPOINT
big18Tzfs yes /big18Tzfs
big18Tzfs/vm-100-disk-0 - -
big18Tzfs/vm-100-disk-1 - -
big18Tzfs/vm-102-disk-0 - -
big18Tzfs/vm-106-disk-0 - -
 
It's a LVM volume path. It's not called rootu by default though.
 
Last edited:
Thanks! fstab has: "/etc/fstab:/dev/pve/rootu/dev/pve/root / ext4 errors=remount-ro 0 1" that is it. What dev is "dev/pve/rootu/dev/pve/root"? There is nothing there?
Most likely this is some typo or an erroneous pasting during editing fstab.

As this path doesn't exist, just comment out this line in fstab.
Then run an update as usual and verify that the warnings are gone :).
 
Thanks Onslow! You're are undoubtedly right! Interestingly, I hadn't noticed before, but in fstab there is a NOTE above this line (the "/etc/fstab:/dev/pve/rootu/dev/pve/root / ext4 errors=remount-ro 0 1" line) that says "# Below added in recovery system and can probably be removed.". Presumably I put it there when I moved to 9? I had some real difficulty going to 9. Anyway, I could take it out, but I wanted to figure out how and where root (/) was actually being mounted. mount shows it as: "/dev/mapper/pve-root on / type ext4 (rw,relatime,errors=remount-ro)". Frankly I started using linux a quarter century ago, and to me, a mount is a logical (/home) to a "physical" (/dev/sda2). I am barely able to keep up when we start talking about zfs subvolumes or LVM (even UUIDs were a jump for me.) Anyway, I finally puttered around enough with LVM (lvscan etc.) and lsblk to convince myself I can remove it. I'm cautious! You can fix pretty much anythhing, but my proxmox is headless and not physically very accessiable. Commenting the line out in fstab! Thanks again.
 
I stripped the results down a bit but this should help to make sense of it
Bash:
# ls -l /dev/pve/root /dev/mapper/pve-root
lrwxrwxrwx 1 root root 7 Jul 20 13:27 /dev/mapper/pve-root -> ../dm-0
lrwxrwxrwx 1 root root 7 Jul 20 13:27 /dev/pve/root -> ../dm-0

# dmsetup ls -oblkdevname
pve-root        (dm-0)

# lsblk -o+PATH,PKNAME,KNAME
NAME                 MAJ:MIN RM   SIZE RO TYPE MOUNTPOINTS PATH                       PKNAME KNAME
sda                    8:0    0    64G  0 disk             /dev/sda                          sda
└─sda3                 8:3    0  63.5G  0 part             /dev/sda3                  sda    sda3
  ├─pve-root         252:0    0  29.9G  0 lvm  /           /dev/mapper/pve-root       sda3   dm-0
See here for more.
 
Last edited:
  • Like
Reactions: Onslow
I am barely able to keep up when we start talking about zfs subvolumes or LVM
@jacobrale
I must admit I'm not good at ZFS either. But LVM can be easily imagined in relation to ordinary disks and partitions.

In the simplest form: first you create a PV from a disk or from a disk partition.
Then you build a VG of one or more PVs.
In a VG you create one or more LVs.
In this imaginary analogy: LV is like a disk partition.
On a LV you create a file system (e.g. ext4) like on a disk partition.

Here you are an image from Wikipedia:
https://upload.wikimedia.org/wikipedia/commons/thumb/e/e6/Lvm.svg/960px-Lvm.svg.png
Various elements of the LVM
 
Last edited: