We have established a cluster of machines in the Astronomy department that are running the Linux operating system. While there are other non-Linux machines (a few Sun workstations, some Windows PCs, and a few Macs), the Linux cluster provides the main computing environment for the academic members of the department.
Linux is a open-source Unix operating system that has been developed by a large number of people. Several different groups distribute the Linux package. We are running RedHat/CentOS Enterprise Linux on our computers; this products has a long support lifetime, and we generally upgrade machines on a several year timescale as convenient.
Every Linux workstation has its own Linux installation, and all packages that come with the installation are located locally on each machine. For software that does not come with the RedHat/CentOS distribution (e.g., astronomy-related software), the software is centrally installed on one of the main Linux servers, astrodisk. The disk with this software is exported and mounted by all of the other machines, so it is accessible to everyone without requiring multiple installations.
The Linux machines are set up as an NIS domain for user accounts, mail aliases, and a few other things. What this means is that account information is kept on a few NIS servers, and all of the other machines query a server for account information. As a result, once you have a Linux account, it works on all of the Linux machines; your password will be the same, regardless of what machine you happen to log into.