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

[Wollie]

@BG405

running in Legacy mode, on a GPT disk

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

[gan]

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.

@Wollie

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

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

[Wollie]

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.

[gan]

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.

[BG405]

@Wollie

prone to fail in my eyes

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.

[Wollie]

@gan

My /home will be not very large, because I will move the system directories (Documents, Videos, Music, etc.) in another disk.

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.

[Wollie]

@BG405

Not experienced any issues myself running several systems including old non-(U)EFI-capable ones.

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.

[gan]

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.

[Wollie]

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.

---

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

[gan]

Yeah, indeed!

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?

[Wollie]

@gan

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!

[stephane]

see theses commands

GRUB restore problem finding the OS

boot on USB iso manjaro open a terminal and returns inxi -Mxa ( check for UEFI only , not UEFI[legacy] or Bios ) test -d /sys/firmware/efi && echo efi || echo bios sudo parted -l sudo efibootmgr -v in your EFI disable secure boot disable fastboot disks on AHCI no legacy no CSM UEFI only or others ( not windows ) you should see UEFI < USB vendor name > < patrition 1 > --> boot in EFI

[TriMoon]

@gan

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].

The main difference that CSM allows is:

• When enabled plus [Uefi and Legacy OPROM] or [Legacy OPROM only] selection made:
  It enables your UEFI-Bios to recognize and boot from the MBR^{(Master Boot Record)} of a medium (HD/USB/CD/DVD).
• When it is disabled or when enabled but [UEFI only] option is selected:
  Your UEFI-Bios will only consolidate the ESP to boot from.

So in short (very simplisticly):

• It is a switch that indicates "Where to search for the boot loader" to your UEFI-Bios.
  So if your Boot Device Control option is set to [Legacy OPROM only] by default; Your UEFI-Bios is in fact instructed to skip the ESP…

---

You should view the ESP as an upgrade of the bootsector that is used in MBR mode:

• The MBR (single sector) can hold only one bootloader.
• The ESP (partition) can hold as many bootloaders as can fit on the partition.
  The order and file (plus arguments) used per boot-entry is stored, inside NVRAM, in what is called EFIVars.
  The default boot entry is stored at \EFI\BOOT\BOOT.efi or \EFI\BOOT\BOOTx64.efi.
  (Backspace usage while referring to files in the ESP is the standard because the partition is of type FAT, eg. M$ filesystem)

---

@gan

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?

The reason why it is being recommended to disable CSM before booting the Live-media is to ensure that it is started in UEFI mode and installs the bootloader in the ESP instead of the MBR.
This is just a precaution to help people that are unaware of the difference.
Hence it is recommended not demanded/required

1. With that default setting, [Legacy OPROM only], you won’t be able to boot the installer in UEFI mode.
2. With the setting [Uefi and Legacy OPROM], the boot mode that the installer starts in by default, depends on weather the bios is set to choose the MBR or UEFI bootloader first. (Which should also be selectable somewhere)
   You should be able to select which one, using the BIOS-boot-menu, because the two versions will have different text indicating UEFI or not.

---

@gan

each of them with their own EFI partition

Make sure to use only 1 “EFI partition” aka ESP when using a single disk.
Because it makes no sense to have multiple, an ESP is meant to hold multiple bootloaders by design.
Plus the UEFI Bios will only consider the first it finds to find the default bootloader in it (\EFI\BOOT\BOOT.efi or \EFI\BOOT\BOOTx64.efi).

---

@gan

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).

You should be able to use both MBR and UEFI boot modes at same time using CSM, as long as you install the respective OS in the correct mode for it.

Beware though that because the MBR can hold only a single bootloader, it might get replaced by installers that react upon presence of a bootloader in the MBR.
That’s why the safest option is to always use "UEFI mode only" on your system when the OS’s you want to use support it.

The only problem you may be left in that case, would be the usage of Secure Boot, which Manjaro and some other distro’s don’t use by default yet.
Because it involves getting a signed signature from M$…

[gan]

First of all, @TriMoon, thank you very much for your detailed and clear explanation.

@TriMoon

This is just a precaution to help people that are unaware of the difference.

It is certainly so, of course. However (especially thinking at a newbie of Linux), we could add: "I recommend that you disable CSM, unless your motherboard has the ability to automatically detect and boot both old systems in Legacy mode and new ones in Uefi mode; you should look for entries like ‘Legacy & Uefi mode’ or similar).
I know some motherboards do not have submenus for the CSM option (especially older laptops). For them, disabling the CSM only assists to disable Secure boot, but unfortunately it does not allow you to take full advantage of sharing multiple operating systems. The newest motherboard’ models no longer even have legacy mode support.

@TriMoon

You should be able to select which one, using the BIOS-boot-menu, because the two versions will have different text indicating UEFI or not.

My Asus motherboard, at first looks for if it is possible to boot the system in Uefi mode, and if not find it, boots it in Legacy mode. On F8 at boot, I can also choose the two modes, as you say.

@TriMoon

Make sure to use only 1 “EFI partition” aka ESP when using a single disk.

I wrote about that choice because I found this @linux-aarhus advice, on archived Manjaro forum:

Shared vs. Separate EFI System Partitions (Windows/Manjaro Dual-Boot)

We all know of the Windows habit snoping around; that’s why it sounded an embraceable advice.

.

@TriMoon

Beware though that because the MBR can hold only a single bootloader, it might get replaced by installers that react upon presence of a bootloader in the MBR .
That’s why the safest option is to always use " UEFI mode only" on your system when the OS’s you want to use support it.

This is one of the motivations that inspired my decision to convert all my systems to Uefi mode, even for those S.Oes which are not perfectly compatible like Win7.
Among other things, maybe someone will be interested, for Win7 x64, which cannot make the conversion without deleting the partition, there is the “free” way to switch from MBR to GPT, even if a little complicated.
There are also some videos on Youtube: for example this one.

[linux-aarhus]

The recommendation to disable CSM is to avoid issues where the existing system is installed using MBR but because the system is EFI-enabled - Manjaro ISO is booted in EFI mode. This has created a heap of forum topics where new members could not make the installation work - because of the mix.

EFI requires GPT and cannot be used - not even installed on an MBR disk.

If you need your system as MBR due to an existing Windows 7 then disable EFI in firmware - if possible - and if not you must install Manjaro to a different disk - not just a different partition - but a different disk.

[gan]

Oh, yes.
But if I have both systems in Efi+Gpt mode, it is still advisable to have two boot partitions for both systems.
I got it right?

[linux-aarhus]

Again - the reason the guide recommends it - is because new members have created a lot topics on how Manjaro disappears after a Windows update.

The recommendations are general - a fail-safe if you like - but if you know what you are doing - then by all means do as you please.

[TriMoon]

@gan

"I recommend that you disable CSM, unless your motherboard has the ability to automatically detect and boot both old systems in Legacy mode and new ones in Uefi mode; you should look for entries like ‘Legacy & Uefi mode’ or similar)

It is easier to just use the frase “recommended” and trust that the reader understands the meaning of that word, instead of explaining in detail “why and when” because that would be needed.
But in that case a “newbie” would not understand it and skip it eitherway.

@gan

I wrote about that choice because I found this @linux-aarhus advice, on archived Manjaro forum:

That only applies to the default bootloader in the ESP i mentioned.
M$ should not interfere with other bootloaders that are installed in the ESP under their own vendor dir, else M$ would be violating it’s own UEFI specs.
It (M$) does however tend to fiddle with the boot-order and default selected boot entry, which can be fixed easily in many ways including the BIOS itself.

@gan

But if I have both systems in Efi+Gpt mode, it is still advisable to have two boot partitions for both systems.
I got it right?

Still wrong as i explained above about the ESP.
Eg. not advisable but possible because it is needless.

PS: You probably have MBR+GPT
(Don’t mix partition-table types and BIOS types)

[gan]

@TriMoon

PS: You probably have MBR+GPT
(Don’t mix partition-table types and BIOS types)

Just for what you say, I would like to have only S.Os. running in EFI mode. Once I have made the effort, it will stay with me for years.

At the moment I have a laptop on which only Manjaro is installed and a desktop with Win7 installed on MBR.
I tried Ubuntu, Mint and then Manjaro on the laptop. After a few months I decided that Manjaro is definitely better than Windows (and the others distros), even if I can’t completely leave Windows.
(Win10 is not even a consideration! )

@TriMoon

But in that case a “newbie” would not understand it and skip it eitherway.

Not all the newbies! I’m a newbie to linux but I want to learn this new system.
I am aware that to convert the current Win7 from MBR+Legacy to GPT+EFI I will have to fiddle a bit with partitions and tools, but I like to experiment with new things.