update_fstab.sh

#!/bin/bash

set -x
set -u

check_fstab () {
    time_stamp=$(date +%F-%H:%M:%S)
    cp /etc/fstab /etc/fstab.backup.$time_stamp
    cp /etc/fstab /etc/fstab.modified.$time_stamp
    sed -n 's|^/dev/\([sx][v]*d[a-z][0-9]*\).*|\1|p' </etc/fstab >/tmp/device_names   # Stores all /dev/sd* and /dev/xvd* entries from fstab into a temporary file
    while read LINE; do
            # For each line in /tmp/device_names
            UUID=`ls -l /dev/disk/by-uuid | grep "$LINE" | sed -n 's/^.* \([^ ]*\) -> .*$/\1/p'` # Sets the UUID name for that device
            if [ ! -z "$UUID" ]
            then
                sed -i "s|^/dev/${LINE}|UUID=${UUID}|" /etc/fstab.modified.$time_stamp               # Changes the entry in fstab to UUID form
            fi
    done </tmp/device_names

    if [ -s /tmp/device_names ]; then
        echo -e "\n\nERROR  Your fstab file contains device names. Mount the partitions using UUID's before changing an instance type to Nitro."                                                         # Outputs the new fstab file
        echo "Writing changes to /etc/fstab..."
        cp /etc/fstab.modified.$time_stamp /etc/fstab
        echo -e "\nOriginal fstab file is stored as /etc/fstab.backup.$time_stamp"
        rm /etc/fstab.modified.$time_stamp
        rm /tmp/device_names
    else
        rm /etc/fstab.backup.$time_stamp
        rm /etc/fstab.modified.$time_stamp
        echo -e "\n\nOK     fstab file looks fine and does not contain any device names. "
    fi
}

check_fstab