GNU Rush is a Restricted User Shell, designed for sites providing limited remote
access to their resources, such as, for example, savannah.gnu.org. Its main
program, rush, is configured as a user login shell for users that are allowed
only remote access to the machine. Using a flexible configuration file, GNU Rush
gives administrator complete control over the command lines that users execute,
and allows to tune the usage of system resources, such as virtual memory, CPU
time, etc. on a per-user basis.