Shells are programs (that are not part of the operating system kernel) that allow you to run programs through the command line and see their output. There are different types of shells available to our customers.
cPanel’s jailed shell came from service providers’ desire to establish a clean cut separation between the various services and customers, mainly for security and ease of administration reasons. Instead of adding a new layer of fine-grained configuration options, the solution adopted was to compartmentalize the system, both its files and its resources, in such a way that only the right person(s) are allowed access to the right compartment(s).
Bourne-Again Shell (bash)
The folks from the Free Software Foundation created an exceedingly souped-up version of the so called Bourne shell with automated command completion and plenty of additional functionality. Linux systems typically choose Bash as the “basic” shell used by default. This is by far the most popular shell used by our customers.
Korn shell (ksh)
Korn shell (ksh) written by David Korn, of Bell Labs, is available on virtually any Unix-like system sold in the 1990’s and beyond.
It’s a reasonable platform for both interactive system control as well as shell script programming, providing far superior functionality to the Bourne Shell. In many cases, it is quite a bit faster, too.
Z Shell (zsh)
Zsh is basically an extended bourne shell with a large number of improvements, including some of the most useful features of bash, ksh, and tcsh.