Create and manage a case-sensitive disk-image on macOS (OS X).

casesafe.sh

#!/bin/bash

# ---------------------------------------------------------
# Customizable Settings
# ---------------------------------------------------------

MOUNT_POINT="${CASE_SAFE_MOUNT_POINT:-${HOME}/casesafe}"
VOLUME_PATH="${CASE_SAFE_VOLUME_PATH:-${HOME}/.casesafe.dmg.sparseimage}"
VOLUME_NAME="${CASE_SAFE_VOLUME_NAME:-casesafe}"
VOLUME_SIZE="${CASE_SAFE_VOLUME_SIZE:-60g}"

# ---------------------------------------------------------
# Functionality
# ---------------------------------------------------------

create() {
    hdiutil create -type SPARSE -fs 'Case-sensitive Journaled HFS+' -size ${VOLUME_SIZE} -volname ${VOLUME_NAME} ${VOLUME_PATH}
}

automount() {
    attach
    cat << EOF > "/tmp/com.${VOLUME_NAME}.plist"
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
    <dict>
        <key>RunAtLoad</key>
        <true/>
        <key>Label</key>
        <string>com.${VOLUME_NAME}</string>
        <key>ProgramArguments</key>
        <array>
            <string>hdiutil</string>
            <string>attach</string>
            <string>-notremovable</string>
            <string>-nobrowse</string>
            <string>-mountpoint</string>
            <string>${MOUNT_POINT}</string>
            <string>${VOLUME_PATH}</string>
        </array>
    </dict>
</plist>
EOF
    sudo cp "/tmp/com.${VOLUME_NAME}.plist" "/Library/LaunchDaemons/com.${VOLUME_NAME}.plist"
    rm "/tmp/com.${VOLUME_NAME}.plist"
}

noautomount() {
    detach
    sudo rm -f "/Library/LaunchDaemons/com.${VOLUME_NAME}.plist"
}

detach() {
    m=$(hdiutil info | grep "${MOUNT_POINT}" | cut -f1)
    if [ ! -z "$m" ]; then
        sudo hdiutil detach $m
    fi
}

attach() {
    sudo hdiutil attach -notremovable -nobrowse -mountpoint ${MOUNT_POINT} ${VOLUME_PATH}
}

resize() {
    compact
    detach
    hdiutil resize -size ${VOLUME_SIZE} ${VOLUME_PATH}
    attach
}

compact() {
    detach
    hdiutil compact ${VOLUME_PATH} -batteryallowed
    attach
}

help() {
    cat <<EOF
usage: casesafe <command>

Possible commands:
    create       Initialize case-sensitive volume (only needed first time)
    automount    Configure macOS to mount the volume automatically on restart
    noautomount  Stop macOS from mounting the volume automatically on restart
    mount        Attach the case-sensitive volume
    unmount      Detach the case-sensitive volume
    resize       Resize the case-sensitive volume
    compact      Remove any uneeded reserved space in the volume
    config       Show current configuration and instructions on changing
    help         Display this message
EOF
}

config() {
    cat <<EOF
The behavior of the script may be modified by setting the following environment variables.
If not set the script will use sane defaults.

CASE_SAFE_MOUNT_POINT
    Location where case-sensitive volume will be mounted
    Current effective value: ${MOUNT_POINT}

CASE_SAFE_VOLUME_PATH
    Location where image file should be stored
    Current effective value: ${VOLUME_PATH}

CASE_SAFE_VOLUME_NAME
    Name of case-sensitive workspace as visible in macOS Finder app
    Current effective value: ${VOLUME_NAME}

CASE_SAFE_VOLUME_SIZE
    Maximum size of volume (will auto-grow up to this)
    Current effective value: ${VOLUME_SIZE}
EOF
}

invalid() {
    printf "casesafe: '$1' is not a valid command.\n\n";
    help
}

case "$1" in
    create) create;;
    automount) automount;;
    noautomount) noautomount;;
    mount) attach;;
    unmount) detach;;
    resize) resize;;
    compact) compact;;
    config) config;;
    help) help;;
    '') help;;
    *) invalid $1;;
esac

For anyone who comes here, I was having the IO issues @tpinne mentioned but as my previous comment indicated I have only been having them since using Big Sur. I have changed the script so that the filesystem is "Case-sensitive APFS" and so far it seems a lot better... I was barely able to run npm install in directories in the mounted workspace before, now it seems to be working as expected

Any ideas on how to encrypt this?

I tried to add hdiutil create -encryption flag and enter a password etc, it works properly when I manually mount it but then when I run

hdiutil isencrypted /dev/disk3s1
encrypted: NO

It says not encrypted 🤔 not sure if i'm not thinkin something through properly though

Unfortunately, I am no longer using this myself, so I can't advise much. I did do a quick search and found this:
https://apple.stackexchange.com/a/178685

That answer specifically mentions Maverisks so is rather old, but if I'm reading it correctly, it sounds like it's possible for macOS to cache an old encryption status of "no" if a drive with the same path/name is remounted as one that was previously encrypted.