Linux – Centos 6.10 – Mount Backup Disk with Single partition

centos6linux

My disk failed and required replacement. I backed up my data on anther disk and the hosting company removed it prior to replacing corrupted disk. Now I have a fresh install (Centos 6.10) and would like to mount the backup disk "sdb". I'm not able to do so as the disk is entirely a single partition.
The command doesnt work:

[root@PGE005 ~]# mount -t ext4 /dev/sdb /mnt/disk2
mount: wrong fs type, bad option, bad superblock on /dev/sdb,
       missing codepage or helper program, or other error
       In some cases useful info is found in syslog - try
       dmesg | tail  or so

Model: ATA MB0500EBNCR (scsi)
Disk /dev/sdb: 500GB
Sector size (logical/physical): 512B/512B
Partition Table: loop

Number Start End Size File system Flags
1 0.00B 500GB 500GB ext4

[root@PGE005 ~]# lsblk -f
NAME   FSTYPE LABEL UUID                                 MOUNTPOINT
sdb    ext4   disk2 2fd32a7c-00f9-4db9-b5bd-139cde166a14
sdc
sdd
sda
├─sda1
├─sda2 ext2         af8372df-bb07-40ec-8f59-65e61576afc0 /boot
├─sda3 swap         ddf30d80-0723-4e66-aa33-52c273e42464 [SWAP]
├─sda4 ext4         076sdr99-13d2-44cf-a230-49c8b3d22c7c /tmp
└─sda5 ext4         3a56e728-b1e7-47a7-bc44-391ea38b8fb6 /

My backup disk is sdb. The hosting provider support said it seems that there is a compatibility issue between the partition formatter and the mounter.
I appreciate any support or ideas that will help me mount the backup disk.

Edit:

[root@pge005 ~]# dmesg | tail
EXT4-fs (sdb): couldn't mount RDWR because of unsupported optional features (400)

Best Answer

The message from dmsg is most helpful. I found several posts about this error, the most promising being on unix.se.

Quotes from there:

The error "EXT4-fs : couldn't mount RDWR because of unsupported optional features (400)" is due to different versions between the partition formatter (mkfs.ext4) and the mounter.

You have two options:

a) Either you have to upgrade the mounter program using a newer distro inside the SD-card.

b) or you have to backup the files, reformat the SD-card with the same distro (the same ext4 versions) you are doing the mounting, and after the reformat copy the files again to the SD-card.

The answer with the most upvotes has this additional tip:

The ext4 feature (400) is the new metadata_csum feature. If this feature is enabled and old tools are used to mount the filesystem they will only be able to mount read-only.

(highlight by me).

Since you basically want to restore your backup, I'd give this a try and mount the disk read only.

mount -t ext4 -o ro /dev/sdb /mnt/disk2
Related Topic