I am dual booting Manjaro KDE and Windows for a while now, and it’s been working like a charm. But two days ago, when booting Manjaro, I encountered the error in the title, Mount /sys/firmware/efi/efivars unknown filesystem type 'efivars'
So I did as suggested in older threads for the same error, and reinstalled Grub. It seemed to work for a while, but today when I tried to boot up Manjaro, the error returned. Again, I reinstalled Grub, but to no avail. I did notice, however, that sometimes when I attempt to boot, the error appears, but Manjaro does eventually boot. In other times, the terminal screen switches to high resolution and remains on the error, unresponsive.
Note: I am on the testing branch and run kernel 5.9. When attempting to run Manjaro with older kernels an error failed to mount /boot/efi appears. Emergency mode however, is not usable, as the keyboard is unresponsive.
but what linux? Please mention name (and version if applicable) of distribution.
Now what happened before that? Please mention it, especially if you ran updates on the other distribution. That’s the only activity that ever touches grub.
Speaking from past outdated experiences, Manjaro’s grub implementation can handle other distros, but other grubs tend to fail booting Manjaro due to some customisation on Manjaro’s part. If that’s the case, please uninstall grub package from secondary distro completely. Then boot into Manjaro and reinstall grub. Manjaro’s grub alone is enough to boot them all.
But we cannot confirm anything without more info. Pastebin the following output.
Fastboot is disabled, CSM is disabled, no secureboot option (I understand that it’s identical with CSM), no choice to switch to BIOS mode, disks are on AHCI, no optabe RST option as far as I can see.
In the boot preferences, beside the option to boot to Manjaro or Windows, there is a UEFI OS option. When I boot it, it shows the error error: symbol 'grub_calloc' not found
and opens up a grub rescue terminal. I am not sure of its significance, if at all.
Translating this message: It means it is not possible to load the EFI firmware as a filesystem.
You get the message when the system is starting in Legacy mode (BIOS mode) - and can be compared to you having two disks to mount in fstab and then you disconnect one and reboot without removing the device from fstab.
The mount error pointing to the missing device on reboot - same thing happening on your system but with the efivars filesystem.
Now I have no idea what have happened - but such thing does not happen overnight so I am fairly sure it is some interaction on your part which have caused it.
It is fairly simple to determine as already pointed to by @stephane the long version is - if this special filesystem is available - you will be able to list the contents - usually it is readonly - but it is possible to mess it by mounting it rw.
Listing the content of efi folder should yield something similar to this output
I didn’t spot that - file system is named efivarfs - the mountpoint is efivars - agree the message appears slightly confusing
I see - that makes a slight difference.
One could speculate - but the information given is sparse to say the least.
In the guide to dual-boot which you find in the #contributions section you are advised - if using EFI - to create a separate $esp for your Manjaro installation. The reason is simple - it is to avoid Windows from rewriting your Manjaro $esp.
Another indication of possible conflict is if you list the partitions on your primary disk and it yields something including the word dos which will indicate you are in fact trying to boot an EFI installation on MBR partition which is impossible - hence the error message. Try list diskinfo using fdisk
I’m afraid it’s a typo on my end, it does say efivarfs. I had a rather large update just a day or so before it started. Perhaps that’s the cause? Or conversely, maybe some windows update indeed bricked it.