If you have installed Linux on your Chromebook, you may have noticed that the file system as viewed from the files application on your Chromebook and the file system in the Linux terminal do not look alike. This is because Linux is running within a container. There are two ways to share files between your Chromebook and the Linux container.
If you open the Files application on your Chromebook, you will see an area called Linux Files. This lets you get access to files in your Linux home directory and read them from Linux doesn’t have immediate access to the files on the Chromebook. To access these, you need to explicitly share the folder with Linux. From the Files application find the folder that you want to share. Right-click on it and select “Share with Linux.” From within Linux if you navigate to the path /mnt/chromeos you will see sub-folders that are mount-points for each of the folders from Chrome that you’ve shared.
You can also share USB drives with Linux. By default, they are not available. If you open Settings and look for “Manage USB Devices” the USB drives that are connected to your machine will be listed. You can select a drive to share with Linux from there. Note that when you disconnect the drive, the next time that it is reconnected it will not automatically be shared.
The Linux container’s ports are also not exposed to your network by default. For the ports to be visible to other devices on your network, you must explicitly share them. Under settings if you look for “Port Forwarding” you will be taken to an interface where you can specify the ports that will be exposed. Note that you can only add ports in the range of 1024 to 65,535.