CSM (Compatibility Support Mode) is disabled on new ASUS mobo

dortmunder · 29 Dec 2021

Hi. I've just built a new PC and have used an ASUS Prime B560M-A (my last one was an ASUS but different model). When I tried to boot into Tails I had no luck and that's when I found out that CSM is disabled on the B560M-A. This is apparently from an ASUS support page:

1. Q: When I use the integrated graphics card on the Intel® 500 series motherboard , why does the CSM option under BIOS appear gray and non-configurable? A: The Intel® 500 series chipset does not support UEFI VBIOS graphic card, hence the integrated graphics mode does not support legacy boot and CSM option becomes non-configurable
2. Q: How can I configure CSM normally? A: You can use a discrete graphics card that supports UEFI VBIOS to make CSM option configurable

I've never used a graphics card. I've also read that if you disable Secure Boot it might enable CSM. The B560M-A isn't black and white when it comes to Secure Boot. This is what I've done in my BIOS:
The heading 'Secure Boot State' says 'setup'. This is greyed out and can't be changed.
For the heading 'OS Type' I've selected Other OS (alt is Windows UEFI)
For the heading 'Secure Boot Mode' I've selected Custom.
Finally, I've gone into Key Management and deleted all the Secure Boot Keys.

Does that mean I've disabled Secure Boot? I'm not sure because when I went into BIOS later there were new Secure Boot Keys...

Any help that lets me boot into Tails very much appreciated!

zebal · 29 Dec 2021

dortmunder said:

When I tried to boot into Tails I had no luck and that's when I found out that CSM is disabled on the B560M-A.

Hi, it would help if you please explain what happens when you attempt to boot tails?
Is there an error message or does the boot process go straight into windows without signaling any error?

Please try to use quick boot menu to confirm tails is given as UEFI boot option.
And if it is, try to boot it that way.

Why is this important, likely you won't see it as UEFI bootable because:

UEFI boot from hybrid ISO cat'd on a USB device: given BIOS DVD boot works generally fine, it's OK to require users to go this way and install their UEFI-capable Tails USB stick from DVD. In case one has no DVD writer, another potentially workable option is to bootstrap in Legacy BIOS boot mode from hybrid ISO cat'd on a USB device. If the firmware supports it, this can be done on the same computer; else, from another computer.

source

Another thing to double check is to make sure your bootable USB is valid, it should be FAT32 formatted and bootable as UEFI.

Try use unetbootin to create bootable tails.
UNetbootin - Homepage and Downloads

Alternative option is to try it with a DVD.

dortmunder · 29 Dec 2021

Hi zebal. The normal Tails GRUB screen appears but then a few lines of text appear (too fast to read) and then it crashes to a black screen. I've tried making the USB with Etcher (recommended by Tails) and with Rufus. Both were boot options when I pressed F8 in the BIOS. My case doesn't have a DVD slot.

zebal · 29 Dec 2021

According to link I gave you, if you want to boot Tails from USB then CSM must be enabled (aka. Legacy BIOS)

But since you can't enable it I see no way to get around this, except...

Can you confirm your downloaded image is USB image and not DVD image?
Tails - Download and verify (for USB sticks)

MaloK · 29 Dec 2021

Hi,

I don't understand, Tails supports UEFI Secure Boot since 2020. You should be able to boot it in Pure UEFI without CSM.

dortmunder · 29 Dec 2021

Yes, verified as USB image.
Hi MaloK. Yes, that's what I thought from my reading of the Tails website (but I'm no expert). I tried the Tails troubleshooting mode which took ages. The only phrases I could understand from all text generated were "Unable to find a medium containing a live file system" and "couldn't allocate usb_device".

MaloK · 29 Dec 2021

@dortmunder, ok thanks I'm going to give it a try and report back...

zebal · 29 Dec 2021

dortmunder said:

"Unable to find a medium containing a live file system" and "couldn't allocate usb_device".

I would reformat USB to FAT32 and try extracting ISO image to USB with unetbootin, that's the only suggestion I have left.
At least unetbootin always worked for me for a lot of linux flavors.

dortmunder · 29 Dec 2021

I tried formatting to FAT32 using the command line. It got to 98% then told me drive was too big for FAT32 (it's 128gb).

zebal · 29 Dec 2021

As far as I know UEFI bootable stick requires FAT32, which file system did you use to format your USB then?

Following might help, see 2nd example with PowerShell:
How to Format USB Drives Larger Than 32GB With FAT32 on Windows