Master Boot Record (MBR) partitioned disks are replaced with newer GUID Partition Table (GPT) standard but MBR is still used widely as a default format. GPT layout for the partition tables has a lot of benefits comparing with MBR one. Along with supporting significantly larger size of disks, it introduces faster and more stable booting. GPT requests to support Unified Extensible Firmware Interface (UEFI) boot.
Switch to root user.
$ sudo su -
Run GPT partition tool. Assuming that sda disk is bootable and will be converted into GPT.
$ gdisk /dev/sda GPT fdisk (gdisk) version 0.8.10 Partition table scan: MBR: MBR only BSD: not present APM: not present GPT: not present *************************************************************** Found invalid GPT and valid MBR; converting MBR to GPT format in memory. THIS OPERATION IS POTENTIALLY DESTRUCTIVE! Exit by typing 'q' if you don't want to convert your MBR partitions to GPT format! ***************************************************************
Make sure that there is enough space before the first partition to support a boot partition. 2048 value for the first sector confirms that GPT can be applied to MBR.
Command (? for help): p Disk /dev/sda: 52428800 sectors, 25.0 GiB Logical sector size: 512 bytes Disk identifier (GUID): 71DD2E79-BD1C-4713-9880-22664C87E57B Partition table holds up to 128 entries First usable sector is 34, last usable sector is 52428766 Partitions will be aligned on 2048-sector boundaries Total free space is 20973501 sectors (10.0 GiB) Number Start (sector) End (sector) Size Code Name 1 2048 2099199 1024.0 MiB 8300 Linux filesystem 2 2099200 16777215 7.0 GiB 8E00 Linux LVM 3 16777216 20971519 2.0 GiB 8E00 Linux LVM 4 20971520 31457279 5.0 GiB 8E00 Linux LVM
Create a new bootable partition. As the first sector, enter 34 and the last sector is 2047. Partition code is ef02.
Command (? for help): n Partition number (5-128, default 5): First sector (34-52428766, default = 31457280) or {+-}size{KMGTP}: 34 Last sector (34-2047, default = 2047) or {+-}size{KMGTP}: Current type is 'Linux filesystem' Hex code or GUID (L to show codes, Enter = 8300): ef02 Changed type of partition to 'BIOS boot partition'
Save changes.
Command (? for help): w Final checks complete. About to write GPT data. THIS WILL OVERWRITE EXISTING PARTITIONS!! Do you want to proceed? (Y/N): Y OK; writing new GUID partition table (GPT) to /dev/sda. Warning: The kernel is still using the old partition table. The new table will be used at the next reboot. The operation has completed successfully.
Notify the operation system about changes. It eliminates rebooting of the system.
$ partprobe
Install GRUB on the new bootable partition.
$ grub2-install /dev/sda Installing for i386-pc platform. Installation finished. No error reported.
Validate the conversion.
$ gdisk /dev/sda GPT fdisk (gdisk) version 0.8.10 Partition table scan: MBR: protective BSD: not present APM: not present GPT: present Found valid GPT with protective MBR; using GPT.
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