JeOS stands for “Just enough operating system” and referrs to an operating system with the bare minimum software installed to run the application required. Ubuntu’s server edition makes it easy to install a JeOS minimal system.
To install a minimal LAMP (Linux, Apache, MySQL, PHP) stack on top of an Ubuntu JeOS instance, simply boot off of an Ubuntu server CD and then when it comes to the install screen, highlight the “Install Ubuntu Server” and then press F4 to bring up the “Modes” menu. From this menu select either “Install a minimal system” or “Install a minimal virtual machine”, depending on whether you are installing a VM or a physical server.
From there, carry on with the rest of the install process and when it comes time for the software selection, check the “LAMP Stack” option. During the install process you’ll be asked for a MySQL root password.
After this is done, you’ll end up with an OS that takes up only about 650MB, compared to the regular Ubuntu server option which takes up 2GB. The main advantage of the smaller size is that the server or VM doesn’t run any unnecessary services or expend any extra resources in keeping superfluous software updated. In addition, if it is a VM, it makes it much easier to transport and turns it into more of an “appliance”