Building a Raspberry Pi 4 NAS and Media Share with Samba and a USB Drive

#!/bin/bash
# prepare_drive.sh - WARNING: erases the drive given as the first argument
# Usage: sudo bash prepare_drive.sh /dev/sda
set -e
DISK="$1"
[ -b "$DISK" ] || { echo "No such block device: $DISK"; exit 1; }
lsblk "$DISK"
read -p "Erase ALL data on $DISK? Type YES: " ans
[ "$ans" = "YES" ] || exit 1

# 1. Create a GPT partition table with one partition using the whole disk
parted -s "$DISK" mklabel gpt mkpart nas ext4 0% 100%
sleep 2
PART="${DISK}1"

# 2. Format as ext4 with the label NAS
mkfs.ext4 -F -L NAS "$PART"

# 3. Create the mount point
mkdir -p /srv/nas

# 4. Add an fstab entry by UUID so the mount survives device renaming.
#    nofail lets the Pi still boot if the drive is unplugged.
UUID=$(blkid -s UUID -o value "$PART")
echo "UUID=$UUID  /srv/nas  ext4  defaults,noatime,nofail  0  2" >> /etc/fstab

# 5. Mount everything in fstab and reload systemd's view of it
systemctl daemon-reload
mount -a

# 6. Create folders and give ownership to the sharing group
groupadd -f nasusers
mkdir -p /srv/nas/private /srv/nas/media
chown -R root:nasusers /srv/nas/private /srv/nas/media
chmod -R 2775 /srv/nas/private /srv/nas/media   # setgid keeps the group on new files

df -h /srv/nas