Daniel Reurich <daniel@???> writes:
> I'd like some other eyes to look over my code and point out any
> improvements/flaw.
>
> I haven't tested the code for setting the GRUB_THEME variable in
> /etc/default/grub (in debian/postinst) and I think it's rather crude to
> do it that way.

Some comments on that:

--------
$DEFAULT_GRUB="/etc/default/grub"
--------

The $ seems to be a syntax error.

--------
update-boot(){
    if [ -n $1 ]; then
        case $1 in
            commented)
                echo -e "\n$DEF_GRUB_COMMENT\n# $DEF_GRUB_SETTING" >> $DEFAULT_GRUB
                return
                ;;
            *)
                echo -e "\n$DEF_GRUB_COMMENT\n$DEF_GRUB_SETTING" >> $DEFAULT_GRUB
                ;;
        esac
    fi     

    if which update-grub2 > /dev/null ; then
        sync
        update-grub2 || true
    fi

    if [ -x /usr/sbin/update-initramfs ]; then
        update-initramfs -u
    fi
}
--------

It should be possible to express this as (untested)

-------
update_boot() {
    if [ "$1" = commented ]; then
            echo -e "\n$DEF_GRUB_COMMENT\n# $DEF_GRUB_SETTING" >> $DEFAULT_GRUB
                return
    fi               

        echo -e "\n$DEF_GRUB_COMMENT\n$DEF_GRUB_SETTING" >>$DEFAULT_GRUB

    if which update-grub2 > /dev/null ; then
            sync
        update-grub2 || true
    fi

    if [ -x /usr/sbin/update-initramfs ]; then
        update-initramfs -u
    fi
}
--------

IMHO, considering the use of printf instead of echo -e is also
worthwhile, as in

printf '\n%s\n#% s\n' "$DEF_GRUB_COMMENT" "$DEF_GRUB_SETTING" >> $DEFAULT_GRUB

--------
       while read confline; do
            case confline in
                $DEF_GRUB_COMMENT)
                    theme_default_conf=true;
                    ;;
                $DEF_GRUB_SETTING)
                    theme_parm="matching"
                    ;;
                "#$DEF_GRUB_SETTING"|"# $DEF_GRUB_SETTING")
                    theme_parm="disabled"
----------

missing ;;

----------
                GRUB_THEME=*)
                    theme_parm="modified"
                    ;;
            esac
        done
---------

This reads from stdin which was probably not intended.