Fix corrupted GPT on FreeBSD

One of the disks in my FreeBSD server reported an issue:

Jul 14 18:00:56 nas kernel: GEOM: da0: the primary GPT table is corrupt or invalid.
Jul 14 18:00:56 nas kernel: GEOM: da0: using the secondary instead -- recovery strongly advised.
Jul 14 18:00:56 nas kernel: GEOM: diskid/DISK-67304734999999999999: the primary GPT table is corrupt or invalid.
Jul 14 18:00:56 nas kernel: GEOM: diskid/DISK-67304734999999999999: using the secondary instead -- recovery strongly advised.

To verify it, first I used gdisk command:

root@nas:~ # gdisk /dev/da0
GPT fdisk (gdisk) version 0.8.10

Caution! After loading partitions, the CRC doesn't check out!
Warning! Main partition table CRC mismatch! Loaded backup partition table
instead of main partition table!

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): q

An alternative way to verify this is to use gpart command:

root@nas:~ # gpart show da0
=>       34  976773101  da0  GPT  (466G) [CORRUPT]
         34  976773101       - free -  (466G)

I think it’s possible use gdisk to repair the corrupted GPT table, but I tried gpart and it worked:

nas:~ # gpart recover /dev/da0
da0 recovered
root@nas:~ # gpart show da0
=>       34  976773101  da0  GPT  (466G)
         34  976773101       - free -  (466G)