Each time I boot into my Ubuntu installation, when I open gdisk I am given the messages:
GPT fdisk (gdisk) version 0.8.8
Type device filename, or press <Enter> to exit: /dev/sda
Caution: invalid backup GPT header, but valid main header; regenerating
backup header from main header.
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.
****************************************************************************
If I just hit w and write the table, then rerunning gdisk without a reboot will open without complaint.
GPT fdisk (gdisk) version 0.8.8
Type device filename, or press <Enter> to exit: /dev/sda
Partition table scan:
MBR: protective
BSD: not present
APM: not present
GPT: present
Found valid GPT with protective MBR; using GPT.
However, when I restart, I'm back to an "invalid backup GPT header". My Ubuntu installation boots just fine using rEFInd, as does my LFS installation. My Win7 installation seems to be currently lost although I'm hoping that will be easily fixed once I get some suitable recovery USB pen/disk etc set up.
What's causing this "invalid backup GPT header"? Should I be worried?