CHAPTER 5 Shells
The new shell must be the full path name for a valid shell on the system. Which shells are available to you will vary from system to system. The full path name of a shell may also vary. Normally, though, the Bourne and C shells are standard, and available as:
Some systems will also have the Korn shell standard, normally as:
Some shells that are quite popular, but not normally distributed by the OS vendors are bash and tcsh. These might be placed in /bin or a locally defined directory, e.g. /usr/local/bin or /opt/local/bin. Should you choose a shell not standard to the OS make sure that this shell, and all login shells available on the system, are listed in the file /etc/shells. If this file exists and your shell is not listed in this file the file transfer protocol daemon, ftpd, will not let you connect to this machine. If this file does not exist only accounts with "standard" shells are allowed to connect via ftp.
You can always try out a shell before you set it as your default shell. To do this just type in the shell name as you would any other command.