Mount APFS volumes as read only

mountAPFSreadOnly.sh

#!/bin/bash

# Usage
# mountAPFSreadOnly device

# Example
# mountAPFSreadOnly /dev/disk8s1

# inspiration via: https://forums.macrumors.com/threads/how-to-mount-an-external-drive-apfs-as-read-only.2241919/post-28578009


#require sudo
if [ "$(whoami)" != "root" ] ; then
    echo "Run this script with sudo" >&2
    exit 1
fi

# stdout is hidden on some commands to make the output make more sense
diskutil unmount $1 > /dev/null
echo "Volume passphrase needed"
diskutil apfs unlockVolume $1 -nomount > /dev/null
diskutil mount readOnly $1