What is the best way to install AnduinOS on a mini PC that is limited to 32GB of EMMC storage but has an SD card slot for extra storage?

[MrStyles02]

What I would like to do: Install AnduinOS on a Minix Z83-4 mini PC. It uses an Intel Z8350 x4 processor. AnduinOS installs and runs fine on the 32GB EMMC but there is not much room for applications. I have a 256GB Extreme Endurance SD card installed. What is the best and safest way to maximize the storage usage? (Moving the home folder to the SD card and mounting the SD card as "home" is not an option, it brakes the desktop - I tried). Chat GPT suggests moving the Package Cache and Large Data Folders to the SD card. Will this solve update issues like "out of disk space"? Is there a way to set the package cache folder location through the GUI?

[Anduin2017]

Hello MrStyles02,

That's a very common challenge with devices that have small EMMC storage. Your approach is correct—moving large data folders is the standard solution. This will definitely help solve "out of disk space" errors during updates, especially given that AnduinOS uses Flatpak, which can store large amounts of application and runtime data.

The AnduinOS documentation provides the correct first step: mounting the SD card as a separate storage device. The key is not to mount it over an existing system folder, but to mount it to its own new directory (like /opt/disk2 in the doc, or more descriptively, /mnt/sdcard).

Here is a detailed plan covering the safe method (moving caches) and the advanced method (moving your entire home folder).

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1. Mount Your SD Card (Following the Guide)

First, follow the steps in the [AnduinOS "Mount your second disk" documentation](https://docs.anduinos.com/Install/Mount-Second-Disk.html) to get your 256GB SD card formatted and auto-mounted.

Here's a summary tailored to your situation:

1. Identify your SD card: Run lsblk. Your 32GB EMMC will likely be /dev/mmcblk0. Your 256GB SD card will probably be /dev/mmcblk1 (it will not be nvme1n1 as in the guide's example).
2. Create a mount point: Let's use a clearer name.

   sudo mkdir -p /mnt/sdcard

3. Format the SD card (Optional): If the card isn't already formatted with a Linux filesystem (like ext4), you should format it. This will erase all data on the card. (e.g., sudo mkfs.ext4 /dev/mmcblk1 or sudo mkfs.ext4 /dev/mmcblk1p1 if you created a partition).
4. Add to /etc/fstab: This is the most important step for making it permanent. Use the device name you found in step 1 (e.g., /dev/mmcblk1) and the mount point from step 2 (/mnt/sdcard).

   # Replace /dev/mmcblk1 with your SD card's actual device name
   echo "/dev/mmcblk1 /mnt/sdcard ext4 defaults 0 0" | sudo tee -a /etc/fstab

5. Mount and Verify:

   sudo mount /mnt/sdcard
   df -Th

   You should now see your SD card mounted at /mnt/sdcard.

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2. Safely Move Large System Folders (The Symlink Method)

This is the safest way to solve your "out of disk space" update errors.

⚠️ Important Warning

As you noted, mounting a disk onto an existing, non-empty folder (like /var/lib/flatpak) will immediately make all the original files in that folder "disappear" (they are hidden by the mount). This will break your system.

The correct process is to move the data first, then create a symbolic link (symlink).

Example 1: Moving Flatpak Data (Highest Impact)

Flatpak apps and runtimes are stored here and are often the largest consumers of space.

1. Create a new home for the data on the SD card:

   sudo mkdir -p /mnt/sdcard/flatpak-data

2. Copy the existing data to the new location: Using rsync is safest as it preserves permissions.

   sudo rsync -avh /var/lib/flatpak/ /mnt/sdcard/flatpak-data/

3. Verify the copy: Check that the files are now in /mnt/sdcard/flatpak-data.
4. Remove the old data folder:

   sudo rm -rf /var/lib/flatpak

5. Create the symlink: This tells the system "When you look for /var/lib/flatpak, actually go to /mnt/sdcard/flatpak-data."

   sudo ln -s /mnt/sdcard/flatpak-data /var/lib/flatpak

Example 2: Moving the Apt Package Cache

This is where downloaded .deb files are stored.

1. Create a new home for the cache:

   sudo mkdir -p /mnt/sdcard/apt-cache

2. Copy the existing cache:

   sudo rsync -avh /var/cache/apt/archives/ /mnt/sdcard/apt-cache/

3. Remove the old cache folder:

   sudo rm -rf /var/cache/apt/archives

4. Create the symlink:

   sudo ln -s /mnt/sdcard/apt-cache /var/cache/apt/archives

You can repeat this "move and symlink" process for any large system folders (like /var/lib/docker if you use it).

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3. Alternative Method: Moving Your Entire Home Directory

You mentioned that moving your home folder and mounting the SD card as /home failed and broke your desktop.

This method is absolutely possible, but it is advanced and fails easily. Your previous attempt most likely failed due to incorrect file permissions and ownership. When you simply copy files (e.g., with cp), you can lose the specific user:group ownership and rwx permissions that your desktop environment needs to log in.

The correct way to do this is with rsync to preserve all attributes, and you must do it while you are not logged into your user's desktop session.

High-Level Steps (Use with Caution):

1. Log out completely: Log out of your desktop environment.
2. Switch to a TTY: Press Ctrl+Alt+F3 to open a virtual terminal. Log in as your user (or as root).
3. Ensure your SD card is mounted: Make sure /mnt/sdcard (from Section 1) is mounted.

   sudo mount /mnt/sdcard

4. Use rsync to copy: This is the critical step. The -a flag preserves permissions, ownership, and all attributes. (Assuming your username is mrstyles02).

   # This copies the *contents* of your home folder into a new directory on the SD card
   sudo rsync -avh /home/mrstyles02/ /mnt/sdcard/mrstyles02_home/

5. Rename the old home: Do not delete it yet! This is your backup.

   sudo mv /home/mrstyles02 /home/mrstyles02_old

6. Create a new, empty mount point:

   sudo mkdir /home/mrstyles02

7. Edit /etc/fstab: This is the final step. Instead of the symlink method, you will tell the system to mount your new SD card directory directly onto /home/mrstyles02. A "bind mount" is the most reliable way to do this.

   # Add this line to /etc/fstab. It binds the directory on the SD card to your home mount point.
   echo "/mnt/sdcard/mrstyles02_home /home/mrstyles02 none defaults,bind 0 0" | sudo tee -a /fstab

8. Mount and Reboot:

   sudo mount /home/mrstyles02
   sudo reboot

9. Log in: If it works, your entire home directory is now running from the SD card, with all permissions intact thanks to rsync.
10. Clean up: Only after you are 100% sure everything works (after several reboots), you can delete the backup: sudo rm -rf /home/mrstyles02_old.

For most users, the symlink method in Section 2 is safer and easier. But if you want to move the entire /home, the rsync and fstab bind-mount method is the correct way to do it.