[solved]difference between legacy_boot and boot for mbr parted

system72 · 2025-11-27 22:04:12

what is the difference? and what partition type do they set on the partition

Last edited by system72 (2025-11-28 20:12:45)

system72 · 2025-11-27 22:08:42

and bios_grub too

V1del · 2025-11-27 23:16:31

Please edit your post instead of double posting/bumping when no one has answered in between.

info parted set wrote:

'bios_grub'
(GPT) - Enable this to record that the selected partition is a
GRUB BIOS partition.
'legacy_boot'
(GPT) - this flag is used to tell special purpose software
that the GPT partition may be bootable.
...
'boot'
(Mac, MS-DOS, PC98) - should be enabled if you want to boot
off the partition. The semantics vary between disk labels.
For MS-DOS disk labels, only one partition can be bootable.
If you are installing LILO on a partition that partition must
be bootable. For PC98 disk labels, all ext2 partitions must
be bootable (this is enforced by Parted).

ergo, the only valid option out of these for MBR is 'boot'

Last edited by V1del (2025-11-27 23:17:00)

system72 · 2025-11-27 23:19:32

ty i couldnt find it in the man page

uhm what partition type does the boot option set

Last edited by system72 (2025-11-27 23:28:09)

V1del · 2025-11-27 23:33:53

These don't exist for MBR (outside of extended or primary and the main relevance of that distinction is that you can't have more than 4 primaries and Windows can't boot from a primary, linux doesn't really care) and that flag has in and of itself no bearing on the type (for general compat you probably want to set that on some primary)

system72 · 2025-11-27 23:37:05

i meant this

V1del · 2025-11-28 01:25:50

Yes and concepts like "GUID" are relevant to the GUID Partition Table and irrelevant on MBR (and are more or less irrelevant on GPT as well, safe for the ESP partition and some special partiitons that make systemd do some automagic mounting, which you can as well control with an fstab

https://wiki.archlinux.org/title/Partit … oot_Record
https://wiki.archlinux.org/title/Partit … tion_Table

system72 · 2025-11-28 18:31:20

so what does the boot option do exactly then

-thc · 2025-11-28 19:54:42

A master boot record has very limited space for the bootstrap code (446 byte) - which is not enough for GRUB. Traditionally following the first sector (on a pure MBR disk) were some unused sectors - GRUB used those for it's (MBR/BIOS mode) code.

In a GPT partition table those sectors are reserved for up to 128 partition entries. You have to create a small, unformatted partition (1-2 MB) and mark it with this flag ("bios_grub") to allow GRUB to store it's code there.

This is only useful for GRUB in MBR mode with a GPT partition table.

"legacy_boot" is for "special purpose software".

"boot" is the traditional boot flag for any kind of boot code or boot manager that needs it.

Last edited by -thc (2025-11-28 20:03:08)

system72 · 2025-11-28 20:03:57

i meant how does parted make the partition bootable when u set the boot option on it

Lone_Wolf · 2025-11-28 20:10:32

For MBR drives it sets a special flag on a partition to mark it as bootable.
GPT drives don't use/need such a flag.

-thc · 2025-11-28 20:10:47

It doesn't. It's just a flag.

The flag "boot" is e.g. for traditional MBR boot code to have a "jump target" for the next step in the boot process.

system72 · 2025-11-28 20:12:33

ok thx everyone i understand how it works better now

Arch Linux

#1 2025-11-27 22:04:12

[solved]difference between legacy_boot and boot for mbr parted

#2 2025-11-27 22:08:42

Re: [solved]difference between legacy_boot and boot for mbr parted

#3 2025-11-27 23:16:31

Re: [solved]difference between legacy_boot and boot for mbr parted

#4 2025-11-27 23:19:32

Re: [solved]difference between legacy_boot and boot for mbr parted

#5 2025-11-27 23:33:53

Re: [solved]difference between legacy_boot and boot for mbr parted

#6 2025-11-27 23:37:05

Re: [solved]difference between legacy_boot and boot for mbr parted

#7 2025-11-28 01:25:50

Re: [solved]difference between legacy_boot and boot for mbr parted

#8 2025-11-28 18:31:20

Re: [solved]difference between legacy_boot and boot for mbr parted

#9 2025-11-28 19:54:42

Re: [solved]difference between legacy_boot and boot for mbr parted

#10 2025-11-28 20:03:57

Re: [solved]difference between legacy_boot and boot for mbr parted

#11 2025-11-28 20:10:32

Re: [solved]difference between legacy_boot and boot for mbr parted

#12 2025-11-28 20:10:47

Re: [solved]difference between legacy_boot and boot for mbr parted

#13 2025-11-28 20:12:33

Re: [solved]difference between legacy_boot and boot for mbr parted

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