home-overlay

#!/bin/sh

set -e

USERNAME=#TARGETUSER#
USERHOME=`getent passwd "$USERNAME" | cut -d: -f6`

OVERLAYD="/run/local/user/$(id -u "$USERNAME")/overlay.d"
WORKD="$OVERLAYD/work"
UPPERD="$OVERLAYD/upper"

overlay_base_mounted () {
    grep -q "^tmpfs $OVERLAYD " /proc/mounts
}

home_overlay_mounted () {
    grep -q "^overlay $USERHOME " /proc/mounts
}

start () {
    if ! home_overlay_mounted; then
        echo "Overlaying $USERNAME home"
        if ! overlay_base_mounted; then
            echo "Preparing overlay base mounts"
            if [ ! -e "$OVERLAYD" ]; then
                mkdir -p "$OVERLAYD"
            fi
            if [ ! -d "$OVERLAYD" ]; then
                echo "Overlay base $OVERLAYD is not a directory"
                exit 2
            fi
            mount -t tmpfs tmpfs "$OVERLAYD"
        fi
        mkdir "$UPPERD" "$WORKD"
        chown -R "$USERNAME" "$UPPERD" "$WORKD"

        mount -t overlay -o "lowerdir=$USERHOME,upperdir=$UPPERD,workdir=$WORKD" overlay "$USERHOME"
    fi
}

stop () {
    if home_overlay_mounted; then
        umount "$USERHOME"
    fi
    if overlay_base_mounted; then
        umount "$OVERLAYD"
    fi
}

case "$1" in
    start)
        start
        ;;
    stop)
        stop
        ;;
    status)
        if home_overlay_mounted; then
            echo "Overlay-mount active on $USERHOME"
        else
            echo "Overlay-mount inactive on $USERHOME"
        fi
        ;;
    *)
        echo "Usage: $0 [start|stop|status]" 1>&2
        exit 1
        ;;
esac