#!/bin/sh
#
# Root filesystem overlay control and install stript
#
# Copyright (C) 2014 Pavel Pisa <ppisa@pikron.com>

# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program.  If not, see <http://www.gnu.org/licenses/>.

modify_boot_cmdline()
{
    if [ ! -e /boot/cmdline.txt ] ; then
        umount_boot=yes
        mount /boot || exit 1
    fi
    if [ ! -e /boot/cmdline.txt ] ; then
        echo "/boot/cmdline.txt missing"
        exit 1
    fi
    if [ ! -w /boot ] ; then
        remount_boot_ro=yes
        mount -o remount,rw /boot || exit 1
    fi
    if ! grep -q '/sbin/init-overlay' /boot/cmdline.txt ; then
        cp /boot/cmdline.txt /boot/cmdline.bak
    fi
    rm -f /boot/cmdline.new
    sed -e 's/\( \|^\)\(ro\|rw\)\( \|$\)/ /g' \
        -e 's/\( \|^\)\(init=[^ ]*\)\( \|$\)/ /g' \
        -e 's/^ //' -e 's/ $//' /boot/cmdline.txt \
        -e 's#^\(.*root=.*\)$#\1'"$1"'#'\
        >/boot/cmdline.new
    mv /boot/cmdline.new /boot/cmdline.txt
    if [ -n "$umount_boot" ] ; then
        umount /boot
    elif [ -n "$remount_boot_ro" ] ; then
        mount -o remount,ro /boot
    fi
}

overlay_is_active()
{
    if [ -e /overlay/robase/overlay ] ; then
        return 0
    else
        return 1
    fi
}

if [ $# -eq 0 ] ; then
    echo "overlayctl [status|enable|disable|lock|unlock]"
    exit 0
fi

if overlay_is_active ; then
    overlay_active="yes"
    overlay_base="/overlay/robase/"
else
    overlay_active="no"
    overlay_base="/"
fi

overlay_disable_file="$overlay_base""overlay/disable"

case "$1" in
    status)
        echo -n "overlay is "
        if [ "$overlay_active" = "yes" ] ; then
            echo "active"
        else
            echo "inactive"
        fi
        echo -n "overlay "
        if [ -e "$overlay_disable_file" ] ; then
            echo -n "disabled"
        else
            echo -n "enabled"
        fi
        echo " for next boot"
        ;;

    enable)
        if [ -e "$overlay_disable_file" ] ; then
            if [ -w "$overlay_base/overlay" ] ; then
               rm "$overlay_disable_file"
            else
               mount -o remount,rw "$overlay_base"
               rm "$overlay_disable_file"
               mount -o remount,ro "$overlay_base"
            fi
        fi
        ;;

    disable)
        if [ ! -e "$overlay_disable_file" ] ; then
            if [ -w "$overlay_base/overlay" ] ; then
               echo 1 >"$overlay_disable_file"
            else
               mount -o remount,rw "$overlay_base"
               echo 1 >"$overlay_disable_file"
               mount -o remount,ro "$overlay_base"
            fi
        fi
        ;;

    lock)
        mount -o remount,ro "$overlay_base"
        ;;

    unlock)
        mount -o remount,rw "$overlay_base"
        ;;

    install)
        modify_boot_cmdline " ro init=/sbin/init-overlay"
        ;;

    uninstall)
        modify_boot_cmdline " ro"
        ;;

    *)
        echo "overlayctl: unknown option"
        exit 1
        ;;
esac