I have a CentOS 7 machine with two disks mounted [ /dev/sda and /dev/sdb ] using ext4.

I need to extend /dev/sdb1 to over 2 TB.

I extended the disk from 2 TB to 2.5 TB (google cloud)

After using fdisk to delete and recreate the partition, after the reboot the resize2fs /dev/sdb1 does not resize the partition to 2.5 TB, since it looks like fdisk has reached the magical 2 TB limit.

Is there a way to extend /dev/sdb1 to lets say 3 TB without losing the data?



as suggested by the fellow serverfault user @mzhaase I tried the gdisk with the following steps. The disk was formated with fdisk in total size of 2T

  1. stop all services using the /dev/sdb1 partition

  2. umount the device

  3. Create a backup/snapshot

  4. Extend the disk to 3T

  5. install gdisk if not already installed on the instance

  6. gdisk procedure
    gdisk /dev/sdb
    p #print and save the GUID
    o #delete all partitions
    n #create new partition
    c #label press ENTER or name if it had it
    x #enter expert mode
    g #paste the GUID
    w #write changes

  7. umount /dev/sdb1 #if it gets remounted by gdisk

  8. e2fsck -f /dev/sdb1 #check disk

  9. resize2fs /dev/sdb1 #resize the partition

  10. mount -a #check if the partitions mount as per fstab

  11. reboot #just to be sure

  • I would not use fdisk on such large disks. It messes up a lot of things! Sep 26, 2016 at 16:45

1 Answer 1


There are two major partitioning schemes in use today: MBR and GPT.

The older, deprecated, and probably still most used one is MBR. However, MBR uses 32 bit to address storage space, using 512 Byte blocks, and 2^32 * 512 Byte are.. 2 TB. So no, you cannot extend an MBR partition over 2 TB. You will need to use GPT for that.

I have never done it myself, but it seems to be possible to convert MBR to GPT without losing data, using gdisk. Try it on your own risk.

  • that means what the data will have to be destroyed and restored from a backup, right?
    – nelasx
    Sep 26, 2016 at 12:42
  • 1
    @nelasx I made another edit. Apparently you can do it without data loss using gdisk. Good luck!
    – mzhaase
    Sep 26, 2016 at 12:45
  • 2
    Taking a backup in any case is prudent if you care about the data. Worst case you do a restore. Sep 26, 2016 at 13:03
  • there is a nice document on docs amazon aws explaining how to do it with gdisk. I tried it on a dev instance and it worked out. aws docs
    – nelasx
    Sep 26, 2016 at 13:06
  • @mzhaase thanks again for your tip on using gdisk it was a life saver.
    – nelasx
    Sep 28, 2016 at 11:37

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