Booting via GRUB 2 prompt

From Jeremy Bryan Smith
Revision as of 03:28, 6 February 2021 by Jeremy (talk | contribs)
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Did your update-initramfs not complete before you rebooted your zfs-on-root Ubuntu install? Here's how to boot it from the GRUB prompt using a previous kernel, assuming that your boot filesystem is on (hd0,gpt3), the zfs dataset name of your boot filesystem is bpool/BOOT/ubuntu/HEAD, the zfs dataset name of your root filesystem is rpool/ROOT/ubuntu/HEAD, and you're wanting to boot version 5.4.0-42-generic of the kernel: 

grub> insmod zfs
grub> set root=(hd0,gpt3)
grub> linux /BOOT/ubuntu/HEAD/@/vmlinuz-5.4.0-42-generic boot=zfs zfs_force=1 root=ZFS=rpool/ROOT/ubuntu/HEAD net.ifnames=0 biosdevname=0
grub> initrd /BOOT/ubuntu/HEAD/@/initrd.img-5.4.0-42-generic
grub> boot

That should load the kernel and initial ramdisk. If you are then dropped to an (initramfs) shell, you'll have to manually import the zpool containing the root filesystem: 

(initramfs) /sbin/modprobe zfs
(initramfs) zpool import rpool -R /root
(initramfs) exit

Note: The following: 

net.ifnames=0 biosdevname=0

was added to the kernel parameters to ensure that all Ethernet device names use the naming scheme ethX for consistency. That part is not necessary.

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