On 30/04/20 10:32, tu...@posteo.de wrote: > Hi, > > recently I switched from the old MBR-scheme to GPT on > my new PC. > > I have two external USB-harddisk, which were partioned/formatted with > a MBR-scheme/MSDOS partition (but were never used to boot from. They are pure > data containers). > > When I connect these to my new PC, only the device is shown: > /dev/sdb, /dev/sdc. > > The kernel is configured (beside other things) as follows: > > # > # Partition Types > # > CONFIG_PARTITION_ADVANCED=y > # CONFIG_ACORN_PARTITION is not set > # CONFIG_AIX_PARTITION is not set > # CONFIG_OSF_PARTITION is not set > # CONFIG_AMIGA_PARTITION is not set > # CONFIG_ATARI_PARTITION is not set > # CONFIG_MAC_PARTITION is not set > CONFIG_MSDOS_PARTITION=y > # CONFIG_BSD_DISKLABEL is not set > # CONFIG_MINIX_SUBPARTITION is not set > # CONFIG_SOLARIS_X86_PARTITION is not set > # CONFIG_UNIXWARE_DISKLABEL is not set > # CONFIG_LDM_PARTITION is not set > # CONFIG_SGI_PARTITION is not set > # CONFIG_ULTRIX_PARTITION is not set > # CONFIG_SUN_PARTITION is not set > # CONFIG_KARMA_PARTITION is not set > CONFIG_EFI_PARTITION=y > # CONFIG_SYSV68_PARTITION is not set > # CONFIG_CMDLINE_PARTITION is not set > # end of Partition Types > > CONFIG_BLOCK_COMPAT=y > CONFIG_BLK_MQ_PCI=y > CONFIG_BLK_MQ_VIRTIO=y > CONFIG_BLK_PM=y > > dmesg shows this: > [14617.672363] usb 2-2: New USB device found, idVendor=1058, idProduct=25a2, > bcdDevice=10.21 > [14617.672364] usb 2-2: New USB device strings: Mfr=1, Product=2, > SerialNumber=3 > [14617.672364] usb 2-2: Product: Elements 25A2 > [14617.672365] usb 2-2: Manufacturer: Western Digital > [14617.672366] usb 2-2: SerialNumber: 575844314132383959393934 > [14617.681660] usb-storage 2-2:1.0: USB Mass Storage device detected > [14617.681737] scsi host10: usb-storage 2-2:1.0 > [14618.725450] scsi 10:0:0:0: Direct-Access WD Elements 25A2 > 1021 PQ: 0 ANSI: 6 > [14618.725594] sd 10:0:0:0: Attached scsi generic sg1 type 0 > [14618.728090] sd 10:0:0:0: [sdb] Spinning up disk... > [14619.748918] ...ready > > I tried different USB ports in a desperate hope of success... > ...no, same problem. > > Interestingly fdisk shows the following: > > host> sudo fdisk -l /dev/sdb > Disk /dev/sdb: 931.49 GiB, 1000170586112 bytes, 1953458176 sectors > Disk model: Elements 25A2 > Units: sectors of 1 * 512 = 512 bytes > Sector size (logical/physical): 512 bytes / 512 bytes > I/O size (minimum/optimal): 512 bytes / 512 bytes
This could be the key. Sector sizes have been changing from 512 to 4096 over many years. If your kernel has been updated to expect/use 4096 byte sectors, it might not be able to read the disk properly. > Disklabel type: dos > Disk identifier: 0x16f2a91f > > Device Boot Start End Sectors Size Id Type > /dev/sdb1 1 1953458175 1953458175 931.5G ee GPT > > The type is shown as GPT...but the drive has a MSDOS partition table. > > Reading my (old) internal harddrive with an external USB docking > station is possible without any problems, though. > > Unfortunatelu I have no space for 1T image of that drive -- otherwise > I would have made an image copy and experiment with that. > > So better ask, than sorry.... ;) > > Is this fixable or did I lost my backups? > Do you have access to an old kernel? The other thing is try using gdisk (or that could be fdisk under another name :-( But some partitioning schemes can write a GPT with protective MBR - if you can find something that will take the MBR and write it as a GPT that might help, too. Cheers, Wol
