dotfiles/root/etc/initcpio/hooks/lukskeyfile

#!/bin/ash

run_hook() {
    # This is a needed kernel parameter for this hook
    if [ -n "$lukskeyfile" ]; then
        modprobe -a -q loop dm-crypt >/dev/null 2>&1
        # Refer to help from `mkinitcpio -H lukskeyfile`.
        IFS=: read rootKeyDev rootKey cryptkeyLoc <<EOF
$lukskeyfile
EOF

        if [ -z "${cryptkeyLoc}" ]; then
            cryptkeyLoc=/crypto_keyfile.bin
        fi

        # Ask user whether to detect the device (detecting may
        # take up a while and asking is faster)
        while true; do
            read -t5 -p "Use external key file? (default: yes, waiting 5s): " yn
            if [ $? -gt 0 ]; then
                echo "Timed out, assuming yes"
                break
            fi
            case $yn in
                [Yy]*)
                    break
                    ;;
                [Nn]*) return 0;;
                "")
                    echo "Default (yes)"
                    break
                    ;;
                *) echo "Please answer yes or no.";;
            esac
        done

        # Resolve and mount the device, in case we can't mount, show error
        echo "Mounting device..."
        if resoleved=$(resolve_device "${rootKeyDev}" $rootdelay); then
            if mount -o noatime "${rootKeyDev}" /mnt>/dev/null 2>&1; then
                # Copy the keyfile present in the device into the
                # ramfs filesystem to be read by dm-crypt
                cat "/mnt/${rootKey}" > "${cryptkeyLoc}"
            else
                echo "Failed to mount ${rootKeyDev} on /mnt"
                /bin/sh
            fi
        else
            echo "Failed to find ${rootKeyDev} containing LUKS root key."
        fi
    fi
}