The shells file contains a list of
login shells on the system. Applications use this file to determine
whether a shell is valid. For each shell a single line should be
present, consisting of the shell's path relative to the root of the
directory structure (/).
For example, this file is consulted by chsh to determine whether an unprivileged user may change the login shell for her own account. If the command name is not listed, the user will be denied the ability to change shells.
It is a requirement for applications such as GDM which does not populate the face browser if
it can't find /etc/shells, or FTP
daemons which traditionally disallow access to users with shells not
included in this file.
cat > /etc/shells << "EOF"
# Begin /etc/shells
/bin/sh
/bin/bash
# End /etc/shells
EOF