SuSE 12 Installation where root and boot are different

SUSE Product Topics SLES Install-Boot
1

Hi all,

I have installed SuSE 12 where root and boot are different file systems. The root is BTRFS and boot is ext4. This installation has subvolumes for root. I have question related to below subvolumes
ID 258 gen 244451 top level 257 path boot/grub2/i386-pc
ID 259 gen 235020 top level 257 path boot/grub2/x86_64-efi

These subvolumes get mounted on same directories. The fstab entries are:
UUID=e13a6b2a-29f4-4eba-87db-d38b00baa6cd / btrfs defaults 0 0
UUID=bc06c806-ee5c-44f7-99f9-bb7c84418ab8 /boot ext4 acl,user_xattr 1 2
UUID=e13a6b2a-29f4-4eba-87db-d38b00baa6cd /boot/grub2/i386-pc btrfs subvol=@/boot/grub2/i386-pc 0 0
UUID=e13a6b2a-29f4-4eba-87db-d38b00baa6cd /boot/grub2/x86_64-efi btrfs subvol=@/boot/grub2/x86_64-efi 0 0

When the /boot/grub2/i386-pc gets mounted on /boot/grub2/i386-pc, the contents of /boot/grub2/i386-pc gets hidden. Since the original contents of /boot/grub2/i386-pc are required for the OS to boot; how does the OS handle this situation?
How should a backup software handle this situation because since the contents are hidden due to the subvolume, it will not backup the original contents and restore will not work as expected?

2

Hi
But a btrfs subvolume is not a block device, so as long as /boot
(UUID=bc06c806-ee5c-44f7-99f9-bb7c84418ab8) backs up and restores, all
should be good?

AFAIK, backing up btrfs is a little different, unless your using dd?
https://btrfs.wiki.kernel.org/index.php/Incremental_Backup

–
Cheers Malcolm °¿° LFCS, SUSE Knowledge Partner (Linux Counter #276890)
SUSE Linux Enterprise Desktop 12 GNOME 3.10.1 Kernel
3.12.44-52.10-default If you find this post helpful and are logged into
the web interface, please show your appreciation and click on the star
below… Thanks!

3

Hi ShilpaN,

[QUOTE=ShilpaN;29433]Hi all,

I have installed SuSE 12 where root and boot are different file systems. The root is BTRFS and boot is ext4. This installation has subvolumes for root. I have question related to below subvolumes
ID 258 gen 244451 top level 257 path boot/grub2/i386-pc
ID 259 gen 235020 top level 257 path boot/grub2/x86_64-efi

These subvolumes get mounted on same directories. The fstab entries are:
UUID=e13a6b2a-29f4-4eba-87db-d38b00baa6cd / btrfs defaults 0 0
UUID=bc06c806-ee5c-44f7-99f9-bb7c84418ab8 /boot ext4 acl,user_xattr 1 2
UUID=e13a6b2a-29f4-4eba-87db-d38b00baa6cd /boot/grub2/i386-pc btrfs subvol=@/boot/grub2/i386-pc 0 0
UUID=e13a6b2a-29f4-4eba-87db-d38b00baa6cd /boot/grub2/x86_64-efi btrfs subvol=@/boot/grub2/x86_64-efi 0 0

When the /boot/grub2/i386-pc gets mounted on /boot/grub2/i386-pc, the contents of /boot/grub2/i386-pc gets hidden.[/QUOTE]

call me blind, but I don’t see where different FS are mounted on the same mount point… subvol=@/boot/grub2/i386-pc goes on /boot/grub2/i386-pc, and subvol=@/boot/grub2/x86_64-efi goes on /boot/grub2/x86_64-efi?

Regards,
Jens

4

The problem is here that mounting of a subvolume is hiding the contents of the directory.

When subvolume is mounted the cotents of directory are:
barebones-esx2-vm8:~ # ls -ltr /boot/grub2/i386-pc/
total 0

Unmount the subvolume -
barebones-esx2-vm8:~ # umount /boot/grub2/i386-pc/

Contents of the directory after umount:
barebones-esx2-vm8:~ # ls -ltr /boot/grub2/i386-pc/
total 1993
-rw-r–r-- 1 root root 6596 Apr 1 07:35 zfsinfo.mod
-rw-r–r-- 1 root root 5508 Apr 1 07:35 zfscrypt.mod
-rw-r–r-- 1 root root 39176 Apr 1 07:35 zfs.mod
-rw-r–r-- 1 root root 15688 Apr 1 07:35 xzio.mod
…

So whenever /boot is getting backedup, the backup software doesnt see the contents of /boot/grub2/i386-pc/ when subvolume is mounted.

Anybody is facing such issue?

Thanks,
Shilpa

5

Hi
I see many more mod files in the listed directory with it mounted as a
subvolume on a normal boot no mounting/unmounting of a subvolume.

I use ext3 for /boot, btrfs for / and xfs for my other data. Something
just doesn’t seem right with your install, I don’t use esx (which from
your hostname would indicate is in use) so unsure if it is something
with this…

Is it possible to install a test system on the hardware and see if it
duplicates?

–
Cheers Malcolm °¿° LFCS, SUSE Knowledge Partner (Linux Counter #276890)
SUSE Linux Enterprise Desktop 12 GNOME 3.10.1 Kernel
3.12.44-52.10-default If you find this post helpful and are logged into
the web interface, please show your appreciation and click on the star
below… Thanks!

6

I will try that; but I am sure installation on VM shouldnt matter.
And I have just followed the Installation process as is; I dont remember doing special here except configuring an MD.

Thanks,
Shilpa

7

Hi Shilpa,

When subvolume is mounted the cotents of directory are:

I see the issue now. To me it looks like these subvolumes were created after the installation… that’s why the filesystems on them are empty.

The question remains… why were these subvolumes created (I see no need for them), I’ve not come across this before. Let’s see what your test install (other branch of this discussion thread) brings up…

Regards,
Jens

8

Hi All,

Yesterday I freshly installed suse 12 on my machine where root and boot are different file systems. The installation gave me a warning that the cross mounts of root subvolumes will shadow the boot and vice-a-verse.
So I believe that nobody will configure their system with cross mounts.

Earlier setup was done by somebody else and that person must have ignored the warning. Sorry for the confusion.

Sorry for the confusion.

And thanks all for replying to this thread.

Thanks
Shilpa