shells - shell database
The /etc/shells file contains a list of valid shells on the system. For each shell, a single line should be present consisting of the shell's absolute path. A hash mark (#) indicates the beginning of a comment; subsequent characters up to the end of the line are not interpreted. Blank lines are also ignored.
Applications can access the list of shells through getusershell(3C). If /etc/shells is not present, the default list of valid shells is:
Invalid shells in /etc/shells could cause unexpected behavior, such as being unable to log in by way of ftp(1).
list of shells on system
See attributes(7) for descriptions of the following attributes:
Restricted shells should not be listed in /etc/shells.