Ensure rrsync subdirectory is a mountpoint.

rrsync-mountpoint

#!/bin/bash
# Simple pre-rsync check to ensure rrsync subdirectory is a mountpoint.
# That is, only allow rsyncing to a mounted drive, and fail otherwise.
#
# Drop-in replacement for rrsync in .ssh/authorized_keys.

rrsync="$HOME"/bin/rrsync

# Assume -ro always comes before the subdirectory, if provided.
if [ $# -eq 0 ]; then
    exec $rrsync
elif [ $# -eq 1 ]; then
    path=$1
elif [ $# -eq 2 ]; then
    path=$2
else
    exec $rrsync
fi

if ! mountpoint -q $path; then
    echo "Path is not a mountpoint: $path" >&2
    exit 2
fi

exec $rrsync "$@"