在SSD安装Ubuntu并将HDD用作Home分区时，如何将deb包与Flatpak软件安装至SSD的问题咨询

Hey Emir, let's work through this step by step—since DEB packages and Flatpaks handle storage differently, we'll tackle them separately:

DEB Packages #

First off, a quick clarification: by default, DEB packages are installed directly to your system's root partition (/), which is your SSD (since that's where you installed Ubuntu). What you're probably seeing is user-specific data or configurations (like browser profiles, app settings) ending up in your /home directory (on the HDD). If you want those bulk data files on the SSD instead, here's how to fix it:

• For apps that let you pick an install location during setup: Look for a "custom path" option in their installation wizard, and point it to a folder you create on your SSD (like /opt/my-apps or a dedicated /ssd-app-data directory).
• For apps that don't offer this choice: You can move their data folders from your /home to the SSD, then create a symbolic link so the app still finds it at the original path. For example, with Firefox:
  1. Create a folder on your SSD (replace your-user with your actual username):

     sudo mkdir /ssd-data/firefox
     sudo chown your-user:your-user /ssd-data/firefox
     

  2. Move your existing Firefox profile data:

     mv ~/.mozilla/firefox /ssd-data/
     

  3. Link it back to the original location:

     ln -s /ssd-data/firefox ~/.mozilla/firefox
     

  This trick works for most apps—just find their data folder in ~/.config/ or ~/.local/share/ and repeat the process.

Flatpaks #

Flatpaks have two main storage areas: system-wide app files live in /var/lib/flatpak/ (which is already on your SSD, since /var is part of the root partition) and user-specific data (like app settings, caches) goes to ~/.var/app/ (your HDD, since /home is there). If you want that user-specific data on the SSD instead, here's what to do:

1. Create a dedicated folder on your SSD for Flatpak user data:

   sudo mkdir /ssd-flatpak-user
   sudo chown your-user:your-user /ssd-flatpak-user
   

2. Move your existing Flatpak user data over:

   mv ~/.var/app /ssd-flatpak-user/
   

3. Create a symbolic link so Flatpak still looks in the right place:

   ln -s /ssd-flatpak-user/app ~/.var/app
   

Alternatively, if you want to set this up for new Flatpaks without moving existing data, add this line to your ~/.bashrc or ~/.profile file to set an environment variable:

export FLATPAK_USER_DIR="/ssd-flatpak-user"

Log out and back in, and any new Flatpaks you install will store their user data on the SSD.

One quick check to confirm: run df -h / in the terminal to make sure your root partition (/) is indeed mounted on your SSD. The output will show the device path (something like /dev/nvme0n1p2 for an SSD) next to the / mount point.

备注：内容来源于stack exchange，提问作者Emir