Simple shell utility to configure an external drive to not auto mount on macOS

noautomount.sh

#!/usr/bin/env bash

# Modified from: https://akrabat.com/prevent-an-external-drive-from-auto-mounting-on-macos/

# Prevent external drives from auto-mounting on macOS

FSTAB=/etc/fstab

# Add a volume as not auto-mounted to the /etc/fstab file
# by its identifier. Also pass in the volume name to add a
# comment on that line so that we can identify it later.
function add_identifier {
    ID=$1
    VOLUME_NAME=$2
    if [ -z "$VOLUME_NAME" ] ; then
        echo "add_identifier() takes two parameters: ID and VOLUME_NAME"
        exit 2
    fi
    
    # get UUID and TYPE from `diskutil info $ID`
    UUID=`diskutil info "$ID" | grep "Volume UUID" | awk '{print $NF}'`
    TYPE=`diskutil info "$ID" | grep "Type (Bundle)" | awk '{print $NF}'`

    # Remove this UUID from fstab file
    sudo sed -i '' "/$UUID/d" $FSTAB

    # Add this UUID to fstab file
    LINE="UUID=$UUID none $TYPE rw,noauto # $VOLUME_NAME"
    printf '%s\n' "$LINE" | sudo tee -a "$FSTAB" > /dev/null
    printf 'Added "%s" to %s\n' "$LINE" "$FSTAB"
}

# Parse df output to find mounted external volumes under /Volumes/ (not /System/Volumes/)
declare -a IDENTIFIERS=()
declare -a TYPES=()
declare -a SIZES=()
declare -a VOLUMES=()

INDEX=0
while IFS=$'\t' read -r id type size volume; do
  IDENTIFIERS+=("$id")
  TYPES+=("$type")
  SIZES+=("$size")
  VOLUMES+=("${volume##*/}")
  ((INDEX++))
done < <(
  df -aYIH | awk -v OFS='\t' '
    { tail = substr($0, index($0, $7)) }
    tail ~ "^/Volumes/" { print $1, $2, $3, tail }
  '
)

# Check if we found any volumes
if [ $INDEX -eq 0 ]; then
    echo "No external volumes found mounted under /Volumes/"
    exit 0
fi

# Display selection menu
echo "Select volume to disable auto-mounting:"
echo ""

for i in "${!VOLUMES[@]}"; do
    NUM=$((i + 1))
    printf "%2d. %-25s %-7s %-7s (%s)\n" "$NUM" "${VOLUMES[$i]}" "${SIZES[$i]}" "${TYPES[$i]}" "${IDENTIFIERS[$i]}"
done

echo ""
read -p "Enter number: " SELECTION

# Validate selection is a number
if ! [[ "$SELECTION" =~ ^[0-9]+$ ]]; then
    echo "Invalid selection: must be a number"
    exit 1
fi

# Convert to array index (0-based)
IDX=$((SELECTION - 1))

# Validate range
if [ $IDX -lt 0 ] || [ $IDX -ge $INDEX ]; then
    echo "Invalid selection: $SELECTION"
    exit 1
fi

# Process the selected volume
echo ""
add_identifier "${IDENTIFIERS[$IDX]}" "${VOLUMES[$IDX]}"

exit 0