SSH into a VirtualBox machine

I use VirtualBox a lot for testing purposes, mainly to experiment with a Linux distribution (to see whether it’s worthwhile to install it on bare metal) and to test procedures that might involve some complex (and maybe “dangerous”) operations.

After you install VirtualBox Guest Additions, things like bidirectional copy-and-paste will work. Some distributions seem to enable and install such additions right from the start (e.g., Fedora, if I’m not wrong). However, there are many situations where you’re installing a distribution in a VirtualBox machine. If Guest Additions are not already working, you will not be able to copy and paste anything. For example, the ISO of Arch Linux even comes in textual mode only, and it’s helpful to be able to copy and paste commands.

In such situations, I prefer to SSH into the virtual machine from a local terminal: copy and paste will work (since I’m in a local terminal). Moreover, the keyboard layout will be the one of the local system (the host). Thus, the keyboard layout will be already configured correctly. While in the virtual machine, you’d have to configure the keyboard layout. Finally, you can quickly transfer files via SSH between the host and the virtual machine without configuring shared folders.

Before being able to SSH in a virtual machine, you need two things:

  • An SSH server up and running in the virtual machine (how to do that depends on the specific Linux distribution)
  • Configure port forwarding in the virtual machine: for instance, all connections to a specific port on the host will be forwarded to port 22 (the default SSH port) on the virtual machine.

I could do the second operation through the “Settings” of the machine. That requires a few dialogs and filling a few table cells. However, I prefer to do that with a single command from the host. For example, I create and configure a new virtual machine, let’s say with the name “My Machine”. When it is not running, I run from the host:

Then, when I start the virtual machine, assuming the SSH server is configured in the virtual machine, I SSH into the machine through the local port 2522. Of course, you can choose any free port number on your host. For example, assuming there’s a user foo in the virtual machine, I run:

Let’s see a complete example.

Let’s say I create a virtual machine called “Arch Gnome” for installing Arch Linux. I configure it appropriately. In particular, I “insert” the ISO of Arch Linux into the virtual CD ROM drive of the machine. Before starting the machine, I run from the host:

Start the virtual machine:

Inside the live environment of Arch Linux, the SSH server is already up and running. However, since we’ll connect with the root account (the only one present), we must give the root account a password. By default, it’s empty, and SSH will not allow you to log in with a blank password. Choose a password. This password is temporary, and if you’re in a trusted local network, you can choose an easy one.

Now, we can connect via SSH to the virtual machine through localhost. If you have already connected via SSH to localhost, you might get an error of the shape:

All you have to do is edit the known_hosts file by removing the offending lines and try again. You will have to remove all the lines that start with “[]:2522”.

Note that we’re using port 2522 because we previously used that for creating the port mapping. Let’s connect to the virtual machine and type the password we have previously specified for the root account inside the virtual machine (Accept the fingerprint, when asked.):

In your local terminal, you see that you get the colors of the virtual machine (now, you’re inside the virtual machine):

The keyboard layout is the one of the host; as usual, you copy and paste the text into the local terminal and run commands in the virtual machine, but more comfortably since you’re in your local terminal. You can also transfer files with “scp”.

For transferring files, you could also configure your file manager to access the “remote” server (the virtual machine) and browse and perform operations on the virtual machine’s file system from your local file manager.

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