Dumping a MBR Partition table to a new (bigger) Disk and using GPT

While fixing a broken harddisk i just put a bigger disk with 3 TB instead of 2 TB into my Server box.
First because i dont trust the harddisk manufactures to sell me the exact same size i’ve got currently and secondly because
i might use that additional 1 TB for some temporary stuff which doesnt need a RAID.

2 TB was still barely usable with fdisk, but 3 TB will not be. Therefore i needed to dump and load the partition table and convert it on the fly. Sounded complicated but its incredibly easy after i found the right switches.

Normally i would use sfdisk to dump and restore partitions in commandline but it doesnt like GPT Partitions.
For this i use gdisk which can handle both Formats. (it even can convert TO MBR if someone has that weird need)

sda is my working 2 TB disk which has some 300GB partitions (i like to split disks in smaller parts, makes the raid rebuild easier).


Device Boot Start End Blocks Id System
/dev/sda1 63 4883759 2441848+ fd Linux raid autodetect
Partition 1 does not start on physical sector boundary.
/dev/sda2 4883760 786140774 390628507+ fd Linux raid autodetect
/dev/sda3 786140775 1567397789 390628507+ fd Linux raid autodetect
Partition 3 does not start on physical sector boundary.
/dev/sda4 1567397790 3907024064 1169813137+ 5 Extended
Partition 4 does not start on physical sector boundary.
/dev/sda5 1567397853 2348654804 390628476 fd Linux raid autodetect
Partition 5 does not start on physical sector boundary.
/dev/sda6 2348654868 3129911819 390628476 fd Linux raid autodetect
Partition 6 does not start on physical sector boundary.
/dev/sda7 3129911883 3907024064 388556091 fd Linux raid autodetect
Partition 7 does not start on physical sector boundary.

Now i just “open” my sda disk with gdisk and gdisk immediately warns me that it will be convert to GPT if i save, which i dont want to.
But gdisk already has the GPT Format in Memory, so i can create a backup of this GPT Format with Command “b” and save it to a file named partitions.

After this i quit gdisk without writing, open my new 3 TB disk (/dev/sdb) and load that partition. gdisk has some commands that say thay load backups but some of them use the GPT backup partition table, but we want to load a saved backup file.
When the backup is loaded i recheck with “p” and save it with “w” if it is ok.

All Commands:


# 2 TB working RAID member
gdisk /dev/sda
> b
Backup> Enter the filename "partitions"
> q
# open the new disk
gdisk /dev/sdb
> r
> l
Restore> Enter the filename "partitions"
> p
> w

One thought on “Dumping a MBR Partition table to a new (bigger) Disk and using GPT

  1. Hi to every one, the contents present at this site are
    really amazing for people experience, well, keep up the nice work fellows.

Comments are closed.