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ReiserFS

Member

Registered: 2014-02-01

Posts: 57

Is it safe to blank first sector (protective mbr) of gpt disk?

I converted my mbr partition table to gpt. I think my old mbr partition table and bootloader code still exist in the first sector of hard. Is it safe to blank it by somthing like this:

dd if=/dev/zero of=/dev/sda bs=512 count=1

ctxfi-user

Member

Registered: 2010-10-31

Posts: 56

Re: Is it safe to blank first sector (protective mbr) of gpt disk?

Make a backup and try it. Some weird firmwares maybe requires something in the first sector. See detailed descriptions: http://www.rodsbooks.com/gdisk/mbr2gpt.html

Edit: Now I remember. Using GPT and booting in BIOS mode maybe require a boot flag on a partition in the mbr:

Some BIOSes and EFIs require that at least one hard disk have at least one MBR partition that's marked as bootable/active to boot in BIOS mode. Since the protective MBR's single EFI GPT (0xEE) partition is not normally flagged in this way, the affected firmware won't boot from GPT disks.

See: http://www.rodsbooks.com/gdisk/bios.html

Last edited by ctxfi-user (2015-08-07 10:52:32)

ReiserFS

Member

Registered: 2014-02-01

Posts: 57

Re: Is it safe to blank first sector (protective mbr) of gpt disk?

thank you. I'm using uefi mode only. can't find answer in the links.

Last edited by ReiserFS (2015-08-07 11:33:03)

ReiserFS

Member

Registered: 2014-02-01

Posts: 57

Re: Is it safe to blank first sector (protective mbr) of gpt disk?

I blanked first 440 byte of disk (bootloader code) and everything was fine. then I blanked whole of first sector (512 byte) and everything breaked! can't boot anyway. fortunately I had a backup of mbr!