[CentOS] Retrieving files from dd backup

Thu Nov 26 22:27:40 UTC 2020
Leon Fauster <leonfauster at googlemail.com>

Am 26.11.20 um 20:10 schrieb H:
> Running CentOS 7 I have a previously combined backup of a disk with three partitions using dd. I now need to restore one single file from this backup and after perusing the internet, specifically https://unix.stackexchange.com/questions/31669/is-it-possible-to-mount-a-gzip-compressed-dd-image-on-the-fly, I have done the following:
> 
> - installed squashfs-tools
> 
> - installed kpartx
> 
> - made a squash image of the dd backup and mounted it
> 
> - used kpartx to create devices for the three partitions under /dev/mapper/loopNpP
> 
> - I can now mount the first partition, which is the EFI partition, and access it
> 
> - the second partition, the boot partition, fails to mount since it has the same UUID as the disk I am using in the computer, and of which it is an earlier dd backup. Since I am not interested in the boot partition - at least not right now - I moved on.
> 
> - I am, however, interested in the third partition which is LUKS encrypted. Running 'cryptsetup luksOpen /dev/sda3 my_encrypted_volume' I can decrypt it with the password
> 
> - trying to mount the decrypted version with 'mount /dev/mapper/my_encrypted_volume /media/my_device' results in a failure message 'mount: unknown filesystem type 'LVM2_member'
> 
> - another website, https://askubuntu.com/questions/766048/mount-unknown-filesystem-type-lvm2-member, suggests I could run vgdisplay to get the UUID and then rename it using vgrename
> 
> But, vgdisplay shows only one vg and I am afraid to rename the VG UUID shown by vgdisplay since it might refer to the VG currently in use...
> 
> Does anyone have any insight or suggestions into the above and how to proceed while being absolutely certain I will not be messing up the running part of the system?
> 

IIRC: Activate the LVM via: vgchange -a y

and mount the logical volume (LV).

LV can be listed with lvs. The device nodes are under /dev/mapper ...

--
Leon