Problem with network shared storage could lead to a damaged file system or even GPT tables, so the gdisk may help in this case.
Here it is a nasty the error:
[root@srv1 ~]# kpartx /dev/loop0
Alternate GPT is invalid, using primary GPT.
loop0p1 : 0 83881984 /dev/loop0 2048
[root@srv1 ~]# parted /dev/loop0
GNU Parted 3.1
Using /dev/loop0
Welcome to GNU Parted! Type 'help' to view a list of commands.
(parted) p
Error: The backup GPT table is corrupt, but the primary appears OK, so that will be used.
OK/Cancel? OK
Model: Loopback device (loopback)
Disk /dev/loop0: 42.9GB
Sector size (logical/physical): 512B/512B
Partition Table: gpt
Disk Flags:
Number Start End Size File system Name Flags
1 1049kB 42.9GB 42.9GB primary
(parted)
So parted reports the backup GPT is damaged, but how to fix it? The solution is to use gdisk and use write “w” command in it. gdisk also shows the exact error with the GPT table with “v” option:
[root@srv1 ~]# gdisk
GPT fdisk (gdisk) version 0.8.10
Type device filename, or press <Enter> to exit: /dev/loop0
Warning! Main and backup partition tables differ! Use the 'c' and 'e' options
on the recovery & transformation menu to examine the two tables.
Warning! One or more CRCs don't match. You should repair the disk!
Partition table scan:
MBR: protective
BSD: not present
APM: not present
GPT: damaged
****************************************************************************
Caution: Found protective or hybrid MBR and corrupt GPT. Using GPT, but disk
verification and recovery are STRONGLY recommended.
****************************************************************************
Command (? for help): p
Disk /dev/loop0: 83886080 sectors, 40.0 GiB
Logical sector size: 512 bytes
Disk identifier (GUID): 7EDF123B-FBC4-4C09-B636-922BD165F862
Partition table holds up to 128 entries
First usable sector is 34, last usable sector is 83886046
Partitions will be aligned on 2048-sector boundaries
Total free space is 4029 sectors (2.0 MiB)
Number Start (sector) End (sector) Size Code Name
1 2048 83884031 40.0 GiB 0700 primary
Command (? for help): v
Caution: The CRC for the backup partition table is invalid. This table may
be corrupt. This program will automatically create a new backup partition
table when you save your partitions.
Identified 1 problems!
Command (? for help): p
Disk /dev/loop0: 83886080 sectors, 40.0 GiB
Logical sector size: 512 bytes
Disk identifier (GUID): 7EDF123B-FBC4-4C09-B636-922BD165F862
Partition table holds up to 128 entries
First usable sector is 34, last usable sector is 83886046
Partitions will be aligned on 2048-sector boundaries
Total free space is 4029 sectors (2.0 MiB)
Number Start (sector) End (sector) Size Code Name
1 2048 83884031 40.0 GiB 0700 primary
Command (? for help): w
Final checks complete. About to write GPT data. THIS WILL OVERWRITE EXISTING
PARTITIONS!!
Do you want to proceed? (Y/N): Y
OK; writing new GUID partition table (GPT) to /dev/loop0.
Warning: The kernel is still using the old partition table.
The new table will be used at the next reboot.
The operation has completed successfully.
And the GPT backup in this loop device is fixed. Executing parted again reports no problems:
[root@srv1 ~]# parted /dev/loop0 print
Model: Loopback device (loopback)
Disk /dev/loop0: 42.9GB
Sector size (logical/physical): 512B/512B
Partition Table: gpt
Disk Flags:
Number Start End Size File system Name Flags
1 1049kB 42.9GB 42.9GB primary
Verify also reports nor error. More options are available:
[root@srv1 ~]# gdisk /dev/loop0
GPT fdisk (gdisk) version 0.8.10
Partition table scan:
MBR: protective
BSD: not present
APM: not present
GPT: present
Found valid GPT with protective MBR; using GPT.
Command (? for help): h
b back up GPT data to a file
c change a partition's name
d delete a partition
i show detailed information on a partition
l list known partition types
n add a new partition
o create a new empty GUID partition table (GPT)
p print the partition table
q quit without saving changes
r recovery and transformation options (experts only)
s sort partitions
t change a partition's type code
v verify disk
w write table to disk and exit
x extra functionality (experts only)
? print this menu
Command (? for help): v
No problems found. 4029 free sectors (2.0 MiB) available in 2
segments, the largest of which is 2015 (1007.5 KiB) in size.
Command (? for help): q
