I am trying to better understand disks, partitions, and partition tables (mbr vs gpt). In the process I checked the disks on one of my machines (single boot ubuntu 20.04), and found that all of my disks are gpt. However I also found out that some of the partitions have a partition table too. What got me even more confused is that the /boot/efi partition is mbr even though it is on a disk that is gpt. At that point I wasn't sure whether the disk was gpt or otherwise so I tried to convert the /boot/efi to gpt but in the process ended up rendering my machine unbootable. When I looked online for how to convert between the two styles I found that the conversion is done on the disk rather than the partition, but I already have my disk partitioned as gpt. So my question can be divided into three parts (and it all depends on my understanding as laid out above being correct):

1- What does it even mean to have a partition table inside a partition?

2- How can a disk be gpt but the /boot/efi partition on it be mbr? And why?

3- If a system has two hard disks, but one operating system, can each one of these disks have their own different partition tables (one mbr the other gpt)?

  • I can answer the 3rd question: Yes, it's perfectly possible. For example some BIOS servers have mbr as boot partition, in order to boot, but GPT data disks, so that these data disks can be greater than 2TB (mbr limit). Also I'll present you another option which I use occasionally: Disks with no partition table or partitions! It's the loop kind, parted's terminology. – Krackout Jun 16 at 18:45
  • I see. So a partition is not really necessary for disks that don't have an os installed on them. Thanks for pointing that out. – cad86 Jun 17 at 8:49

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