Re: update-grub fails saying it cannot find a device for /

[Randy Goldenberg]

The mounts listed would appear to be on the system hosting the chroot, and do 
not include the root file system that you want grub to work with.

Presumably, you have a partition somewhere that contains the root file system 
that you want to work with in your chroot.  First, mount that partition:

mount /dev/your_partition_containing_rootfs /mnt

Then, if you have separate partitions for things like /var and /tmp and so on, 
mount those too.  Eg.:

mount /dev/your_partition_containing_var /mnt/var

Don't forget to mount your EFI partition at /mnt/boot/efi, if booting UEFI.

A good source for information regarding the file system on the target rootfs 
would be /mnt/etc/fstab.

Mount /sys, /proc, /dev, and /run.  Eg.:

mount --bind /dev /mnt/dev

When complete, chroot into the root file system you have mounted, and do your 
grub business:

chroot /mnt /bin/your_shell



On Sunday November 14, 2021, Stefan Blachmann wrote: 

> Here is it:
>
> 541 33 0:50 / /home rw,relatime shared:309 - zfs rpool/home rw,xattr,posixacl
> 557 33 0:52 / /opt rw,relatime shared:317 - zfs rpool/opt rw,xattr,posixacl
> 572 33 0:53 / /root rw,relatime shared:325 - zfs rpool/home/root
> rw,xattr,posixacl