Whether one physical disk only can have one MBR sector?

If a disk is bootable disk, the first sector of it is MBR sector.

So, is this mean one physical disk only can have one MBR sector, right? there is have nothing to do with the disk partition, right?

so, if use MBR boot, there can only have one OS in one disk, right?


There is a doubt in my mind, we know one disk can be divide into four primary partitions. the primary partition also named as bootable partition. so, what's the meaning of it?

can one disk install multi OS ?

  • 2
    Since the MBR is by definition the 1st sector on a disk, how many 1st sectors can a disk have? – mosvy Jul 24 '19 at 7:38
  • 1
    Yes, there could be only one MBR, which could define only up to four basic partitions. One of which could be an extended partition. So, in fact there is no set limit to the number of OS per physical disk. – Isaac Jul 24 '19 at 7:47
  • @mosvy only one. haha, if one disk install multi OS, there should use GRUB to realize it? – 244boy Jul 24 '19 at 7:47
  • The MBR on a classical PC disk contains a partition table and a small "program" that reads the 1st sector from the primary partition which is marked "bootable" and jump into it. grub or other advanced bootloader may replace that small program with their own, which may do something different, like booting off an extended partition or a different disk. – mosvy Jul 24 '19 at 8:32
  • The first primary partition marked bootable. With only MBR it didn't make sense to mark one than one (primary) partition bootable, but it made old versions of dos/windows (I haven't used it in many years) ignore such partitions, which you could use to make any subsequent partitions have the same name in different versions of dos/windows booted from different partitions marked bootable (you needed a third party bootloader to do that). – Henrik supports the community Jul 24 '19 at 9:46

Can one disk install multi OS ?

Yes, one HDD or SSD can have multiple OS on it and you can select which to boot with with GRUB2 or a similar program, as explained here.

Yes, one LiveUSB can have multiple OS on it, and you can select which to boot with if the LiveUSB was created with an app such as MultiBootUSB, Multisystem, Sardu, WinSetupFromUSB, Xboot, and YUMI.

  • PS: unix.stackexchange.com/help/dont-ask explains questions should have limited scope; in practices, that suggests one question per post; multiple questions should result in multiple posts. – K7AAY Jul 24 '19 at 17:14

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