simple tool to apply overlayfs over specific directories

cursors.sh

#!/bin/sh

# Directory to store overlays in (one directory structure is created per overlay configured down below)
OVERLAY_BASE=/home/root/overlays

overlay() {
        set -e
        overlay_id="$(echo $1 | sed 's;/;__;g')"
        unset TARGET SOURCE FSTYPE OPTIONS
        eval $(findmnt -P $1)
        if [[ "$FSTYPE" == "overlay" ]]; then
                echo "[-] Overlay '$1' already mounted"
        else
                echo "[ ] Preparing overlay for '$1' -> $OVERLAY_BASE/$overlay_id"
                mkdir -p "$OVERLAY_BASE/$overlay_id/upper" "$OVERLAY_BASE/$overlay_id/work"
                mount -t overlay -o lowerdir=$1,upperdir=$OVERLAY_BASE/$overlay_id/upper/,workdir=$OVERLAY_BASE/$overlay_id/work/ overlay-$overlay_id $1
                echo "[+] Overlay '$1' mounted"
        fi
}

# Usage:
overlay /usr/share/im
# now /usr/share/im is read-writable