#!/bin/sh

# Try more ways how to activate filesystem support
#  i.e. check for compiled in option or if modprobe or insmod suceed
insmodule()
{
    if ! /bin/grep -q $1 /proc/filesystems ; then
        /sbin/modprobe $1 >/dev/null 2>/dev/null
        if ! /bin/grep -q $1 /proc/filesystems ; then
            if [ -d "${rootmnt}/lib/modules/$(uname -r)/extra/$1" ] ; then
                /sbin/insmod "${rootmnt}/lib/modules/$(uname -r)/extra/$1/$1.ko"
                if [ $? -eq 0 ]  ; then
                    echo $1
                fi
            fi
            if [ -d "${rootmnt}/lib/modules/$(uname -r)/kernel/fs/$1" ] ; then
                /sbin/insmod "${rootmnt}/lib/modules/$(uname -r)/kernel/fs/$1/$1.ko"
                if [ $? -eq 0 ]  ; then
                    echo $1
                fi
            fi
        else
            echo $1
        fi
    else
        echo $1
    fi
}

if [ -e "/overlay/disable" ] ; then
    echo "Overlay disabled"
    exec /sbin/init
fi

# If no specific overlay support is selected, try all known options
if [ -z "$OVERLAY" ] ; then
    OVERLAY="aufs overlay overlayfs unionfs"
fi

if [ ! -e /proc/filesystems ] ; then
    /bin/mount -n -t proc -o "nodev,noexec,nosuid" proc /proc
    proc_local_mount=y
fi

if grep -q '\( \|^\)overlay=disable\( \|$\)' /proc/cmdline ; then
    echo "Overlay disabled by command line argument"
    if [ -n "$proc_local_mount" ] ; then
        /bin/umount -n /proc
    fi
    exec /sbin/init
fi

for i in $OVERLAY
do
    OVERLAY=$(insmodule $i)
    [ "$OVERLAY" = "$i" ] && break
done

# For initrd for NFS diskless RO root
#ovr_rwdata=/tmp/unirw
#ovr_robase=${rootmnt}
#ovr_combined=${rootmnt}
#ovr_for_nfs=nfs

#For local system rearranged from init
/bin/mount -n -t tmpfs none /overlay
/bin/mkdir -p /overlay/rwdata
/bin/mkdir -p /overlay/robase
/bin/mkdir -p /overlay/combined
/bin/mount --bind / /overlay/robase

ovr_rwdata=/overlay/rwdata
ovr_robase=/overlay/robase
ovr_combined=/overlay/combined

# Prepare filesystem for local data storage...
/bin/mkdir -p ${ovr_rwdata}
/bin/mount -n -t tmpfs none ${ovr_rwdata}

case "$OVERLAY" in
    overlay) echo "Remounting root as overlay ..."
        mkdir -p ${ovr_rwdata}/data
        mkdir -p ${ovr_rwdata}/work
        /bin/mount -n -t overlay -o upperdir=${ovr_rwdata}/data,workdir=${ovr_rwdata}/work,lowerdir=${ovr_robase} overlay ${ovr_combined}
        ;;
    overlayfs) echo "Remounting root as overlayfs ..."
        /bin/mount -n -t overlayfs -o upperdir=${ovr_rwdata},lowerdir=${ovr_robase} overlayfs ${ovr_combined}
        ;;
    aufs) echo "Remounting root as aufs ..."
        /bin/mount -n -t aufs -o dirs=${ovr_rwdata}=rw:${ovr_robase}=${ovr_for_nfs}ro aufs ${ovr_combined}
        ;;
    unionfs) echo "Remounting root as unionfs ..."
        /bin/mount -n -t unionfs -o dirs=${ovr_rwdata}=rw:${ovr_robase}=ro unionfs ${ovr_combined}
        ;;
    *) panic "Actual initrd.img or system has not a module for overlay filesystem"
        ;;
esac

if [ -n "$proc_local_mount" ] ; then
    /bin/umount -n /proc
fi

# Move rwdata mount under new prepared filesystem to allow access
# to local rwdata in case of tmpsfs
/bin/mkdir -p ${ovr_combined}/overlay/rwdata
/bin/mount -n --move ${ovr_rwdata} ${ovr_combined}/overlay/rwdata
/bin/mkdir -p ${ovr_combined}/overlay/robase
/bin/mount -n --move ${ovr_robase} ${ovr_combined}/overlay/robase
/bin/mkdir -p ${ovr_combined}/overlay/pivot
chmod 755 ${ovr_combined} # Disable rw access for non-root users

/bin/touch ${ovr_combined}/fastboot

# Create standard mount points for virtual filesystems
/bin/mkdir -p ${ovr_combined}/dev
/bin/mkdir -p ${ovr_combined}/proc
/bin/mkdir -p ${ovr_combined}/sys
/bin/mkdir -p ${ovr_combined}/tmp
/bin/mkdir -p ${ovr_combined}/run
/bin/mkdir -p ${ovr_combined}/var/lock

cd ${ovr_combined}

echo "Ready to proceed by pivot_root"
#sleep 5
#/bin/sh

/sbin/pivot_root . overlay/pivot
exec /usr/sbin/chroot . sbin/init