shells file contains a list of valid shells
available on the system. A shell is a command line interpreter that reads user
input and executes commands. For each shell a single line should be present,
consisting of the shell's path, relative to root.
A hash mark (‘#’) indicates the beginning of a
comment; subsequent characters up to the end of the line are not interpreted
by the routines which search the file. Blank lines are also ignored.
The chpass(1) program will not
let regular users change their default shell to one not listed in the
shells file. The
ftpd(8) daemon denies access to users who
are not using one of the listed shells.
shells file format appeared in