This is a quick demonstration on formatting your external device for Ubuntu, specific to Crouton Ubuntu installations on Chromebooks. I’ll be using an SD Card and formatting it to ext4 with the partition utility GParted.
Step 1: Install and run GParted via the terminal in your Ubuntu environment:
sudo apt-get install gparted
Next, in order to start the GUI, simply:
In the top right you’ll see a drop down menu for drives. You should easily recognize which is the external drive by it’s size and is commonly found at: dev/sdb1
Note: If you want to see a list of your devices, open a separate terminal window and enter: lsblk
After selecting the external device that you wish to format from the drop down, right click and delete any partitions currently present. If the option to delete is grayed out, then you have to choose to unmount the device first. Then go back and delete.
Now right click the device and choose New. In the next window, make sure Create as: is set to Primary Partition and File system: is set to ext4. Choose a label (I advise against using spaces in the label) and click +Add. Finally, click the green check to apply the operation:
Now quit GParted, close anything else and shutdown your Ubuntu environment to return to Chrome OS so your external device will remount. Wait a moment after the terminal completely exits the chroot and then launch it again re-entering Ubuntu.
Step 2: Setting permissions and ownership. Launch the terminal and enter the following commands (replace with your username and drive label).
sudo chmod +x /media/removable/LABEL
sudo chown -R USERNAME:USERNAME /media/removable/LABEL
Your external device is now formatted to ext4 and is ready for use.