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na_ftpd - File transfer protocol daemon
options ftpd.enable on
FTPD is the Internet File Transfer Protocol (FTP) server
process. The server uses the TCP protocol and listens at
the well-known port (21) for ftp.
Requests
The FTP server currently supports the following FTP
requests; case is not distinguished.
- ABOR
- Aborts previous command.
- ACCT
- Specifies account (ignored).
- ALLO
- Allocates storage (without using space).
- APPE
- Appends to a file.
- AUTH
- Security mechanism
- CCC
- Clears command channel.
- CDUP
- Changes to parent of current working
directory.
- CWD
- Changes working directory.
- DELE
- Deletes a file.
- EPRT
- Specifies data connection port (IPv4 or IPv6).
- EPSV
- Prepares for passive mode transfer (IPv4 or
IPv6).
- HELP
- Gives help information.
- LIST
- Gives list files in a directory (ls -lg).
- MKD
- Makes a directory.
- MODE
- Specifies data transfer. mode
- NLST
- Gives name list of files in directory (ls).
- NOOP
- Does nothing.
- PASS
- Specifies password.
- PASV
- Prepares for server-to-server transfer.
- PBSZ
- Protection buffer size
- PORT
- Specifies data connection port.
- PROT
- Data channel protection level.
- PWD
- Prints the current working directory.
- QUIT
- Terminates session.
- RETR
- Retrieves a file.
- RMD
- Removes a directory.
- RNFR
- Specifies rename-from file name.
- RNTO
- Specifies rename-to file name.
- STOR
- Stores a file.
- STOU
- Stores a file with a unique name.
- STRU
- Specifies data transfer structure.
- TYPE
- Specifies data transfer type.
- USER
- Specifies user name.
- XCUP
- Changes to parent of current working
directory.
- XCWD
- Changes working directory.
- XMKD
- Makes a directory.
- XPWD
- Prints the current working directory.
- XRMD
- Removes a directory.
The remaining FTP requests specified in RFC 959 are
recognized, but not implemented.
The FTP server aborts 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 RFC 959.
The FTP server interprets file names according to the
"globbing" conventions used by sh(1). This enables users
to use the metacharacters: * ? [ ] { } ~.
The FTP server authenticates users according to two rules:
First, the user name must be in the password database,
/etc/passwd, and have a password that is not NULL. A
password must always be provided by the client before any
file operations can be performed.
Second, if the user name is "anonymous" or "ftp", an entry
for the user name ftp must be present in the password and
shadow files. The user is then allowed to log in by
specifying any password -- by convention this is given as
the user's email address (such as user@mycompany.com). Do
not specify a valid shell in the password entry of the ftp
user, and do not give it a valid password (use NP in the
encrypted password field of the shadow file).
For anonymous ftp users, the FTP server takes special
measures to restrict the client's access privileges. The
server performs a chroot(2) command to the home directory
of the "ftp" user.
Ftpd logs all commands to the /etc/log/ftp.cmd file.
Ftpd logs all transfers to the /etc/log/ftp.xfer file.
/etc/passwd
/etc/log/ftp.cmd
/etc/log/ftp.xfer
Postel, Jon, and Joyce Reynolds, File Transfer Protocol
(FTP), RFC 959, Network Information Center, SRI
International, Menlo Park, Calif., October 1985.
Ford-Hutchison, Securing FTP with TLS, RFC 4217, IBM UK
Ltd. October 2005.
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