/etc/shells
is a text file which contains the full pathnames of valid login shells.
This file is consulted by
chsh(1)
and available to be queried by other programs.
Be aware that there are programs which consult this file to
find out if a user is a normal user.
E.g.: ftp daemons traditionally
disallow access to users with shells not included in this file.
This page is part of release 3.14 of the Linux
man-pages
project.
A description of the project,
and information about reporting bugs,
can be found at
http://www.kernel.org/doc/man-pages/.