About CSM, Uefi and booting Manjaro/Win7 in dual boot

in this forum it is often recommended to disable CSM before installing manjaro.
My desktop Asus motherboard, however, allows you to enable CSM and under ‘Boot Device Control’ choosing between:
[Uefi and Legacy OPROM], [Legacy OPROM only], and [UEFI only].

Now I have Windows 7 installed on MBR and the previous Bios option is setup on [Legacy OPROM only] (the default).

If I boot from a live USB manjaro ISO, I can verify that I’ve boot (obiouvsly) in Legacy Bios mode.
I tried to set the option to [Uefi and Legacy OPROM], and this time:

:maple_leaf:) I’ve booted the Live usb in Uefi mode;

:maple_leaf:) Pressing F8 key during Post, I can see (and choose) to start both Uefi mode and Bios (legacy) mode.
(I’ve checked this with the command: ls /sys/firmware/efi)

:maple_leaf:) Windows7 boots fine and always in legacy mode.

But then, when it is recommended to disable CSM option, perhaps it would not be better to specify that it is also possible to leave it enabled as long as your motherboard has the possibility to choose whether to boot the systems in both ‘Legacy’ and ‘Uefi’ modes?

My question arises from the desire to convert my Win7 from MBR to GPT, booting Win in Uefi and then install Manjaro and using it in Uefi mode (each of them with their own EFI partition).

If I understand the UEFI stuffs correctly, I believe it is not necessary to disable CSM completely. Am I right?
Otherwise, I would be forced to use Manjaro in Legacy Mode (and not be able to use more than 4 partitions).

Are you planning on using Win7’s “convert GPT” utility? That should work (I did it on one of my systems years ago). Probably no need to disable CSM but it might be a good idea to do so to make sure you are installing Manjaro in (U)EFI mode.

When booted from the Live USB or DVD run
[ -d /sys/firmware/efi ] && echo UEFI || echo BIOS
in a Terminal to check which mode you’ve booted with.

Note: I use GPT for both Legacy and (U)EFI systems and have done so for some time with mo issues.

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You are fully right, booting in legacy in a mbr parted disk is still a proper way, and no need to change anything. You only have to accept that a mbr parted disk only carries 4 primary partitions (though one can be switched to an extended to carry many more inside) and that your boot disk is limited to max. 2 TiB.

Why so complicated? You can also just install Manjaro in legacy/BIOS mode.

As I said, you can convert one of the four primary partitions to an extended partition and can use logical partitions inside. For Manjaro it does not matter if it’s installed on a primary or a logical partition inside of an extended partition.

Hi, @BG405.
I run [ -d /sys/firmware/efi ] && echo UEFI || echo BIOS
and efibootmgr and I can confirm that when I choose to boot in Uefi the Live, that’s ok.

You are right, @Wollie, but in the future, who knows, maybe I will need to use discs of more than 2 tb and I thought it was better to do things now than when I have customized my Manjaro.
I’m undecided…
In any case, if I left both systems in MBR, would I be better off making the boot partition as a separate primary partition, in your opinion?

You can use larger disks just not for the disk you are now going to install your system. So, as long as your current disk is not larger, no problem. You also can use other disks with gpt.

That’s the nice thing - you don’t need any boot partition, just / and if you like /home and /swap. You can boot Windoze then from grub’s boot menu.

With regard to booting with grub and mbr there is a pretty nice wiki entry which explains it in detail.

Boot doesn’t have to be in a separate partition but it is the way I do it. Give it about ½GB & there should be enough room for a few kernels. No problem just having / with /boot within it but I’d probably suggest separate /home and maybe swap partitions.

No, not for BIOS/legacy boot with MBR parted disk. You are talking about UEFI/gpt systems or combination BIOS/gpt. Believe me, I use a triplicate BIOS/MBR system!

Oh yeah. I did not think about it! :clown_face:
The system disk is large enough for both windows and Manjaro.

Yes, for ease for backup, I will make the /home partition only for user configs. Data will go in other partitions/disks.

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I do this for both. The system I’m on is UEFI capable but running in Legacy mode, on a GPT disk, with those partitions I mentioned.

This is mainly for future-proofing and I intend to convert this installation to UEFI booting at some point. I prepare all disks with GPT these days regardless of whether it’s for a BIOS or (U)EFI installation.

I somehow missed the last part of your reply first time I read it. Triplicate indeed :smiley:

This is a special configuration, prone to fail in my eyes and not recommendable for newbies…

I don’t know for Manjaro, but in Windows7 I have not (intentionally) the “Reserved partiton”. When I installed it, I choose to wipe it and mount the boot directory in in the system directory.

Yes, I think so too. I see that MBR->Legacy mode and GPT->Uefi is “cleaner”

For Manjaro you only need to think about how many partitions you want to use, if needed think about the extended partition to ensure you can create enough partitions. / is the only essential partition, /home is helpful for backups and /swap could be replaced by a swapfile if you prefer to avoid that partition. Having swap is recommended but not nessecarily as partition.

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Right, in my laptop I don’t have a partiton, but the swap file. My /home will be not very large, because I will move the system directories (Documents, Videos, Music, etc.) in another disk.

This might be a bit OT for this thread but I’d be interested to know more about it (I might start a thread on this). Not experienced any issues myself running several systems including old non-(U)EFI-capable ones.

In that case I would recommend not to use a separate /home partition, simply not needed, makes your install easier. Normally BIOS/legacy boot should be combined with a MBR parted disk.

A sign that you know how to implement this right (just to mention the BIOS_grub partition) and don’t use too weird boot packages. :+1:

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But if I have two partitions for root and /home, I could make two separate backup.
For example, if I accidentally deleted a system file on the root partition, I could only restore from the root’s backup. So the recovery would be faster and, in my view, more orderly.
Same thing if the reverse happens: if kde messes with my config files, I can quickly restore only /home.
I am using this method on my laptop.
As a backup program I use fsarchiver, which can contain more than one partition in its backup. When restoring, you can safely choose one or more partitions to restore.

Maybe a little complicated to describe but believe me, once everything is set up it is very fast. :wink:

That’s the nice on Linux there are many possible solutions and you can choose what fits your needs best. Some like a /home partiton, others don’t, so select what you feel right for you. :smile:

I backup my system (just /) using timeshift, and store my data files in a separate partition.

Yeah, indeed! :blush:

I have been switching to linux not long ago.
I’ve spent 20 years with Windows and have always been passionate about various backup strategies, since the days of DOS.

Now I’m testing my strategy with Manjaro.
Maybe if I find it interesting I could write my first tutorial here (for us, poor newbies). What do you think of it?

Of course, just stay tuned, you always find a helping hand here!