lsblck to find the volume in order to mount it:
lsblk NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT xvda 202:0 0 8G 0 disk └─xvda1 202:1 0 8G 0 part / xvdg 202:96 0 100G 0 disk └─xvdg1 202:97 0 100G 0 part loop0 7:0 0 89.1M 1 loop /snap/core/8213 loop1 7:1 0 7M 1 loop /snap/rg/15 loop2 7:2 0 89.1M 1 loop /snap/core/8268 loop3 7:3 0 4.7M 1 loop /snap/rg/7 loop5 7:5 0 7.4M 1 loop /snap/rg/23
In this case the volume in question is
/xvdg, and we just need to mount the partition located at
mount /dev/xvdg1 /mnt/recovery
At this point the problematic volume will be available at
/mnt/recovery. Conduct your investigation and/or repair and proceed with the next steps to restore the fixed volume back to the root partition of the original EC2 instance.
umount -d /mnt/recovery
Find the volume in question in the console:
Volumes -> Actions -> Detach Volume
Now that the volume is fixed, we'll reattach as the root instance
At this point hopefully the original instance is fixed and you'll be able to log back on.