Mount External Storage to Mini PC Server

Most homelab servers — whether it’s a Raspberry Pi or a mini PC — don’t ship with a ton of storage. My mini PC has 512GB, which is fine for running containers but fills up fast once you start hosting media with something like Immich. I had a 2TB Western Digital external hard drive sitting around, so I plugged it in via USB and mounted it as extra storage. If you’re looking to do the same, this guide walks through the full process.

Step 1: Plug in the Drive

Connect your USB hard drive to the mini PC. Make sure it’s detected by the system:

lsblk

Look for your drive (e.g., /dev/sdb1) (yours might be different).

Step 2: Format the Drive (if needed)

Using ext4 is effectively required if you want Immich to manage its library smoothly on a Linux server. If your drive isn’t formatted, create a filesystem. For example, to format as ext4:

sudo mkfs.ext4 /dev/sdb1

Step 3: Create a Mount Point

Decide where you want the drive to be accessible:

sudo mkdir -p /mnt/immich/library

Step 4: Mount the Drive

Mount it manually to test:

sudo mount /dev/sdb1 /mnt/immich/library

Verify it’s mounted:

df -h
lsblk

Step 5: Set Permissions

Immich’s Docker container runs as UID 1000, so give the directory correct ownership (my user id is 1000, you can check yours with id -u):

sudo chown -R 1000:1000 /mnt/immich/library

This ensures the container can read/write files on the drive.

Step 6: Auto-Mount at Boot

Get the UUID of the drive:

sudo blkid /dev/sdb1

Edit /etc/fstab to mount it automatically:

sudo nano /etc/fstab

Add a line like this:

UUID=your-drive-uuid /mnt/immich/library ext4 defaults 0 2

Replace your-drive-uuid with the actual UUID from the blkid command.

Test the fstab entry:

sudo mount -a

If no errors, it will auto-mount on every boot.

Step 7: Use in Docker

Reference the path in your .env for Immich (or whatever container you are using this for, in my case it’s for Immich):

UPLOAD_LOCATION=/mnt/immich/library

Make sure the Docker container maps this directory:

volumes:
  - ${UPLOAD_LOCATION}:/data

Setting Up the Immich Database Folder

Immich uses PostgreSQL to store all the metadata for your media (users, albums, tags, thumbnails, etc.). To make sure this data persists and works correctly with Docker, we set up a dedicated folder on the mini PC, not the external drive: /opt/immich-db.

Step 1: Choose a Local Folder

We’ll use /opt/immich-db for the database:

sudo mkdir -p /opt/immich-db

/opt is a standard Linux location for optional software and data. This keeps the database separate from your media files.

Step 2: Set Correct Permissions

PostgreSQL inside the Docker container runs as UID 999. The folder must be writable by this user:

sudo chown -R 999:999 /opt/immich-db

This ensures the container can read/write database files without errors.

Step 3: Map the Folder to Docker

In your docker-compose.yml, mount the folder to the Postgres container:

volumes:
  - ${DB_DATA_LOCATION}:/var/lib/postgresql/data

Docker maps /opt/immich-db on the host to /var/lib/postgresql/data in the container. PostgreSQL will store all metadata there, persisting even if you update or restart containers.

It’s also best practice to define the path in your .env file:

DB_DATA_LOCATION=/opt/immich-db

Step 4: Start the Containers

After setting up the folder and .env, start Docker:

docker compose up -d

On the first run, Postgres initializes the database in /opt/immich-db. Subsequent restarts will reuse the existing database, keeping all your metadata intact.

Step 5: Permissions & Maintenance Tips

If you ever change Postgres users or reset the database, make sure the folder is cleared carefully:

sudo rm -rf /opt/immich-db/*
sudo chown -R 999:999 /opt/immich-db

Never put the database on a NAS or network share — Immich requires local storage for the DB.

Verify logs:

docker logs -f immich_server

A Note on ext4 and Reusing the Drive

Since we formatted the drive as ext4, it’s fully compatible with anything you’d run on Linux. ext4 is the default Linux filesystem — Docker containers, Samba shares, media servers, backups — it all works out of the box.

The only downside is that ext4 isn’t natively readable on Windows or macOS. But since the drive lives on your server and everything accesses it through Linux, that won’t matter.

You’re also not limited to using this drive for just Immich. You can create additional directories and mount them into other containers. For example:

sudo mkdir -p /mnt/data/whatever

Just keep permissions in mind — different containers may run as different UIDs, so set ownership accordingly for each directory.