mount_nvme.sh

set -o pipefail
set -o errtrace
set -o nounset
set -o errexit
set -a

# Scratch mount is the device which will be mounted on /mnt
# and generally used for logs, core dumps etc.
if ! $(mount | grep -q /mnt) ; then
    # Detected NVME drives
    # They do not always have a consistent drive number, this will scan for the drives slot in the hypervisor
    # and mount the correct ones, with sda1 always being the base disk and sdb being the extra, larger, disk
    if lshw | grep nvme &>/dev/null; then
        for blkdev in $(nvme list | awk '/^\/dev/ { print $1 }'); do
            mapping=$(nvme id-ctrl --raw-binary "${blkdev}" | cut -c3073-3104 | tr -s ' ' | sed 's/ $//g')
            if [[ ${mapping} == "sda1" ]]; then
                echo "$blkdev is $mapping skipping..."
            elif [[ ${mapping} == "sdb" ]]; then
                echo "$blkdev is $mapping formatting and mounting..."
                mkfs -t ext4 ${blkdev}
                echo "${blkdev}    /mnt    ext4    defaults,comment=cloudconfig    0    2" >> /etc/fstab
                mount ${blkdev}
            else
                echo "detected unknown drive letter $blkdev: $mapping. Skipping..."
            fi
        done
    else
        echo "Configuring /dev/xvdb..."
        mkfs -t ext4 /dev/xvdb
        echo "/dev/xvdb    /mnt    ext4    defaults,comment=cloudconfig    0    2" >> /etc/fstab
        mount /dev/xvdb
    fi
else
    echo "detected drive already mounted to /mnt, skipping mount..."
    lsblk | grep mnt
fi

Adapted this recently, but aws now reports the mapping as ephemeral0:sdb instead of just sdb, so adjusted to work as:

            elif [[ ${mapping} == "ephemeral0:sdb" || ${mapping} == "sdb" ]]; then

(also nvme wasn't installed by default, so had to add an apt install nvme-cli -y before the run)