You can remotely use some Linux machines in the
labs of Malá
Strana. Those are u-pl1.ms.mff.cuni.cz to
u-pl37, as of writing this. Use the ssh client
shipped with your Unix/Linux/Mac installation to reach those machines, for
example:
$ ssh your-login@u-pl5.ms.mff.cuni.cz
If you want a different system, you can install it into a virtual machine, for example VirtualBox, QEMU, or VMWare.
To access Unix machines from a Windows installation, you can use a widely used SSH client PuTTY. Windows 10 is already shipped with OpenSSH as beta.