[SOLVED] Back up Partition Table and MBR Manually

snmcdonald · 12-23-2012, 05:00 PM

How do you back up your partition table for a GPT system?

For a regular MBR and MBR partition it would be:

Quote:

dd if=/dev/sda of=/etc/mbr.bak conv=notrunc bs=512 count=1

How many bytes must I copy for a GPT table?

rknichols · 12-23-2012, 05:29 PM

Quote:

Originally Posted by snmcdonald

How do you back up your partition table for a GPT system?

For a regular MBR and MBR partition it would be:

Code:

dd if=/dev/sda of=/etc/mbr.bak conv=notrunc bs=512 count=1

Watch out! That saves only the layout of the primary partitions. If one of those is an extended partition, none of the info for the logical partitions within it will be saved.

Quote:

Originally Posted by snmcdonald

How many bytes must I copy for a GPT table?

You have to calculate that from the fields in the GPT header.

snmcdonald · 12-23-2012, 07:32 PM

Quote:

Originally Posted by rknichols

Watch out! That saves only the layout of the primary partitions. If one of those is an extended partition, none of the info for the logical partitions within it will be saved.

Extended would be tricky as it appears to have varied offsets: wiki:EBR:examples

This has a nice solution: http://www.cyberciti.biz/faq/howto-copy-mbr/

Backup

Code:

# dd if=/dev/sda of=/tmp/backup-sda.mbr bs=512 count=1
# sfdisk -d /dev/sda > /tmp/backup-sda.sfdisk

Restore

Code:

# dd if=backup-sda.mbr of=/dev/sda
# sfdisk /dev/sda < backup-sda.sfdisk

Quote:

Originally Posted by rknichols

You have to calculate that from the fields in the GPT header.

This blog gives the solution as:

Code:

# dd if=/dev/sda of=/etc/gpt.bak bs=512 count=34 conv=notrunc

GPT is 34 LBA... This assumes LBA is 512bytes... parted /dev/sda print or fdisk -l /dev/sda should list the sector/physical size.