GPT on legacy BIOS as extravagant?

Continuing the discussion from Provide details when seeking assistance:

Most curious... Why is this considered a significant deviation from standard installation? I assume I should not go as far to interpret it as "not recommend".

Detailed explanation here

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It's not "not recommended".

There's nothing wrong with using GPT on Legacy - which is what I do since many years.

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I don't want to be a "my uncle drinks and his liver is fine" kind of guy but I've been using GPT on legacy BIOS for almost a decade on multiple systems, including dual-boot configurations and two notebooks and I have never encountered any issues that to my knowledge would indicate their origin in using GPT. The article does honestly report the probability of encountering problems to be very low though.

It's ironic that I'm just in the process of converting my main backup-only drive to 'stupidly standard' i.e. MBR with NTFS and standard allocation unit size. Previously I had, wait for it, GPT with ext4, probably non-standard allocation size aaaand... LVM, without even having a true understanding of how LVM should be handled. The most idiotic thing I did in my entire Linux journey!:star_struck:

For those particular reasons is not recommended :slight_smile: but, is possible to use it with no problem. I had mixed experiences. Cheers!

If you use a standard partition layout for manjaro for example it creates a lower number of primary partitions than MBR has a limit for, so using GPT which requires a small bios_boot partition on a legacy BIOS machine is fairly redundant in that scenario.

GPT makes more sense if you install a couple of operating systems, have a drive larger than 4TB or have a reason to split one OS install into many smaller partitions, including a few for different user data partitions for example. GPT can speed up boot time compared to MBR, but it can only speed up the first few seconds of the boot. And depending on your hardware, it may not speed it up enough to be noticed.

To have a bios-legacy system on a gpt device requires a bios-grub partition and flagged as such.
In this case, there would be no problem, as @anon23612428 is doing.
And the only reason, IMO, to do so is when the disk is > 2 TB size as a msos disk cannot handle sizes above that. But of course, we can still proceed with this setup if the size is below that. The question is why and we can debate about this all night, but we are not going to do that (er.. I'm not).

The problem is that even without that bios-grub partition (and of course nothing to flag) it is still possible to install a bios-legacy system on this gpt disk and we are going to face numerous problems with it (after installation). And that is the reason I put in the point about stating whenever anyone uses a bios-legacy system with a gpt disk. Even if the system is properly setup (with grub-bios partition and flagged), people should state so because others will assume, if noting the disk is gpt, that the system is uefi when it is not.

Even more 'egregious' is when people install install a uefi system on an msdos disk.
Again, unfortunately, the installer allows this thing to happen.

The main point is that one should always state clearly if the system is not of 'the standard procedure'.

Cheers. Hope that explains.


I use legacy MBR boot and msdos partition table on the SSD containing my controlling grub. It's a smaller drive anyway so there was no need for more partitions than can be handled by msdos partition table.


  • my second drive is > 2TB and contains the rest of my distro collection.
  • 3rd drive is the Data drive, also > 2TB
    So those 2 are gpt formatted. But they are not my boot disk.

Even then I sometimes wonder whether some installers might have an issue with installing on GPT partition, on a disk that is not the one containing the MBR.

Most modern distros can handle it, but I had some strange results with Solus installer, and also the really old slackware ncurses installer.

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@gohlip Perfectly clear!

I'm sure I started using GPT just because I'm alergic to cruft and I'm eager to jump on fresh implementations but at least at one point I used GPT because of the ability to have multiple primary partitions. Probably for distro testing.


In msdos partitioning, the extended partition allows quite a lot (forgot how many, but at least 15) logical partitions and that let us install quite a number of OS's too. I remember I had 15 OS's installed in an msdos drive once (right now in my msdos/bios-legacy system, I have 7 OS's).
Just to point out this out in case others here think there is some 'severe' limitation in using msdos disks.

Its actually a unlimited number of partitions can mounted in a extended partition Source Arch Wiki.

I think there is a limit, but it is far far more than 15 (but definitely more than 15)
I think it is over 250 logical partitions, not sure and I cannot be certain.
I had a discussion with @wongs long ago but we cannot confirm the figure.
Can you provide the link if it is definitive ? Thanks.

Here you go
Master Boot Record (partition table)

There are 3 types of partitions in the MBR scheme:


Primary partitions can be bootable and are limited to four partitions per disk or RAID volume. If the MBR partition table requires more than four partitions, then one of the primary partitions needs to be replaced by an extended partition containing logical partitions within it.

Extended partitions can be thought of as containers for logical partitions. A hard disk can contain no more than one extended partition. The extended partition is also counted as a primary partition so if the disk has an extended partition, only three additional primary partitions are possible (i.e. three primary partitions and one extended partition). The number of logical partitions residing in an extended partition is unlimited. A system that dual boots with Windows will require for Windows to reside in a primary partition.

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This probably changed somewhere along the road. Or perhaps Microsoft's implementation was flawed in the past. On my previous Dell XP machine and my Asus laptop that came with Win 7, the max was 15 partitions. I even think it was 15 in total, including the extended partition itself (sda4).

I know this because I had tried on both machines previously to use more partitions than that. On my XP, I was so green at first that I initially thought I needed a different swap partition for each distro and I also had separate /home partitions for each. On my Asus, it was because I was so into installing and trying new distros.

It will appear as if you can create a 16th partition (Gparted proceeds per normal), but when you actually try to install a distro on it, you can't.

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Thanks wongs. I now remembered we disagreed. I recall I said it is much much more.
Anyway, even if it is only :laughing: 15 partitions, It is much more than anyone would likely to use and we're unnecessarily 'punctilious' about it. :slight_smile:


ps: now there is also a limit on the number of gpt partitions as well
and it is again much much much more than the limit of msdos partitions.
But we are not going start 'arguing' (in a nice way, of course not toxic) about that, are we? :rofl:

Ummmm, no comment. :grin:

OK OK, you've twisted my arm...

Confession time - right now I have 15 distros on the PC that replaced the XP machine. It's a combination of 2 distros on my mdos partitioned SSD, and 13 on the GPT-formatted HDD at /dev/sdb.

I could have more than 13 on that drive of course and actually did in the past, but I have deleted those.

How can someone have the time to use all of them, you ask? Well, just boot into a different distro everyday. With a shared Data drive on /dev/sdc, it's no big deal.

Nah, we're too chill.

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Or too jaded. :sunglasses:

@gohlip "No cruft" bias it was then for me! No reason to rationalize! :wink:

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Part 2 of my "extravagant disk config adventures" :confused:

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