ftpd(8) CLIX ftpd(8)
NAME
ftpd - Internet File Transfer Protocol (FTP) server
SYNOPSIS
usr/ip32/tcpip/ftpd
DESCRIPTION
The ftpd server initializes the Internet File Transfer Protocol (FTP)
server process. The ftpd server uses the Transmission Control Protocol
(TCP) and listens at the port specified in the ftp service specification
(see services(4)). The server is normally started by the inetd server.
The ftpd server currently supports the following FTP requests; case is not
distinguished.
ABOR Aborts previous command.
ALLO Allocates storage (vacuously).
APPE Appends to a file.
CDUP Changes to parent of current working directory.
CWD Changes working directory.
DELE Deletes a file.
HELP Gives help information.
LIST Gives a list of files in a directory (ls -ls).
MKD Makes a directory.
MODE Specifies data transfer mode.
NLST Gives a name list of files in a directory (ls).
NOOP Does nothing.
PASS Specifies password.
PASV Prepares for server-to-server transfer.
PORT Specifies data connection port.
PWD Displays the current working directory.
QUIT Terminates session.
2/94 - Intergraph Corporation 1
ftpd(8) CLIX ftpd(8)
RETR Retrieves a file.
RMD Removes a directory.
RNFR Specifies rename-from filename.
RNTO Specifies rename-to filename.
STOR Stores a file.
STOU Stores a file with a unique name.
STRU Specifies data transfer structure.
TYPE Specifies data transfer type.
USER Specifies username.
XCUP Changes to parent of current working directory.
XCWD Changes working directory.
XMKD Makes a directory.
XPWD Displays the current working directory.
XRMD Removes a directory.
Additional FTP requests specified in Internet RFC 959 are recognized, but
not implemented.
Client Access Restrictions
The ftpd server takes special measures to restrict client access
privileges. The ftpd server authenticates users according to the
following three rules:
⊕ The username must be in the password database, /etc/passwd, and not
have a null password. A valid password must be provided by the client
before any file operations may be performed. (The anonymous and ftp
usernames are exceptions to this rule.)
⊕ The username must not appear in the file /etc/ftpusers.
⊕ If the username is anonymous or ftp, one of these accounts must be
present in the password file. In this case the user is allowed to log
in by specifying any password (by convention this is given as the
client host's name). User's access is then restricted to the
subdirectories of the account. In the last case, ftpd takes special
measures to restrict the client's access privileges. The server
performs a chroot command to the home directory of the "ftp" user. In
2 Intergraph Corporation - 2/94
ftpd(8) CLIX ftpd(8)
order that system security is not breached, it is recommended that the
"ftp" subtree be constructed with care; the following rules are
recommended.
~ftp Make the home directory owned by user ftp and unwritable by anyone.
~ftp/bin
Make this directory owned by the superuser and unwritable by
anyone. The ls command must be present to support the list
commands, and sh must be present to support the pwd command. These
programs should have mode 111.
~ftp/dev/null
Create this directory with the command mknod ~ftp/dev/null c 1 2.
~ftp/pub
Make this directory mode 777 and owned by user ftp. Users should
then place files which are to be accessible via the anonymous
account in this directory.
EXAMPLES
The ftpd server is spawned by the inetd daemon when an FTP request is made
by the user (on the client side).
FILES
/etc/ftpusers Configuration file disallowing specified usernames from
using FTP.
/etc/passwd Password file.
/etc/services Service name database.
NOTES
The ftpd server will timeout and exit after 15 minutes of an inactive
session.
The ftpd server will abort an active file transfer only when the ABOR
command is preceded by a Telnet ``Interrupt Process'' (IP) signal and a
Telnet ``Synch'' signal in the command Telnet stream, as described in
Internet RFC 959.
The ftpd server interprets filenames according to the globbing conventions
used by the sh command. This allows users to utilize the following
metacharacters: asterisk (*), question mark (?), open bracket ([), close
bracket (]), open brace ({), close brace (}), and tilde (~).
CAUTIONS
2/94 - Intergraph Corporation 3
ftpd(8) CLIX ftpd(8)
The anonymous and ftp accounts are inherently dangerous and should be
avoided when possible.
DIAGNOSTICS
Error messages are displayed to the console and are prepended with FTP
Server:. Following are some examples of ftp error messages.
Lost connection with the remote client.
There was an unexpected shutdown by the FTP client.
Cannot send FTP command to the remote client.
There was an error in the write() function to the client.
Other error messages are related to the functions connect(), read(), and
so on.
EXIT VALUES
The ftpd server exits with a value of 0 if successful. If unsuccessful,
it exits with a nonzero value.
RELATED INFORMATION
Commands: ftp(1), inetd(8), sh(1)
Files: services(4)
4 Intergraph Corporation - 2/94