ProFTPD: Supported FTP Commands

Supported FTP Commands

ABOR

ALLO
Short for ALLOcate.

APPE
Short for APPEnd.

AUTH
Short for AUTHenticate (supported by mod_tls)

CDUP
Short for Change Directory UP, this command is used to move the client's "location" on the server up one level in the filesystem hierarchy.

CLNT
Short for CLieNT, this command is used by clients to offer/provide any freeform identification they desire to the server.

CWD
Short for Change Working Directory.

DELE
Short for DELEte, this command is used by the client to tell the server to delete a file.

EPRT
Short for Extended PoRT, an enhanced version of the PORT command that can handle IPv6 addresses.

EPSV
Short for Extended PaSsiVe, an enhanced version of the PASV command that can handle IPv6 addresses.

FEAT
Short for FEATures, this command is used by the client to request a descriptive list of server-supported features.

HASH
This command is used by clients to request the checksum, or "hash", of a file on the server. This command is available when the mod_digest module is compiled/loaded.

HELP

HOST
This command is the equivalent of HTTP's "Host" header for FTP, providing the ability to have name-based virtual hosting.

LANG

LIST

MDTM
Short for MoDification TiMe, this command is used by the client to request the modification time of a file on the server. This command is defined formally in RFC 3659, and is a commonly implemented FTP command. Note that this command cannot be used to change the modification time of the file on the server; it only reports on the file's modification time. The MFMT command is used to change a file's modification time.

MFMT
Short for Modify Fact: Last Modified Time, supported by mod_facts. Some clients use this command to change the last modified timestamp on a newly uploaded file so that the timestamp on the server matches the timestamp of that file on the client.

MKD
Short for MaKe Directory.

MLSD
Short for Machine LiSting, Directory, supported by mod_facts. Unlike the LIST command, whose response format was never specified, the MLSD command has a strictly defined response format (see RFC 3659 for details). This format was designed to be easily machine parseable, for automated processing of directory listing formats; the format was also designed to be platform-agnostic, and thus portable.

MLST
Short for Machine LiSTing, supported by mod_facts. This command is similar to MLSD in that it uses the same response format. Unlike MLSD, the response for a MLST is sent back on the control connection rather than using a data connection, and is for a single file only.

MODE
There are three mode types defined by RFC 959; proftpd only supports one (i.e. Stream).

NLST
Short for Name LiST.

NOOP
Short for NO OPeration. This command has no functionality, and is often used as a session keepalive mechanism.

OPTS
Short for OPTionS. This command is used to specify optional parameters for the command to follow the OPTS command, if that command supports such optional parameters.

PASS
Short for PASSword, the client uses this command to convey the password of the user attempting to log into the server.

PASV
Short for PASsiVe, the client uses this command to ask the server for a port to which the client should connect, indicating a passive data transfer.

PBSZ
Short for Protection Buffer SiZe. Used to determine the size of a buffer needed for secure handshaking (supported by mod_tls)

PORT
The client uses this command to tell the server to what client-side port the server should contact; use of this command indicates an active data transfer.

PROT
Short for PROTection. Used to set the protection level on the data channel (supported by mod_tls)

PWD
Short for Print Working Directory.

QUIT

RANG
Short for RANGe, this command is used by clients to request that a specific range of bytes be transferred for files, including uploads and downloads; supported by mod_xfer and defined by this IETF Draft.

REST
Short for RESTart, this command is used by the client to tell the server that it would like to restart a previous data transfer, either upload or download.

RETR
Short for RETRieve, this command is used by the client to inform the server of the file the client would like to download. On many FTP client, this is implemented using the client-specfic "get" command.

RMD
Short for ReMove Directory, this command is used to have the server delete the requested directory from its filesystem.

RNFR
Short for ReName FRom.

RNTO
Short for ReName TO.

SITE
This command is used for site-specific commands. See below for descriptions of proftpd's SITE commands.

SIZE

SSCN
Short for Set Secured Client Negotiation, this non-standard command is used by FTPS clients to tell a server to use TLS when performing a site-to-site transfer. For more details, see here.

STAT

STOR
Short for STORe, this command is used by the client to tell the the server that the client will be uploading data for a file to stored on the server using the filename given. On many FTP clients, this is implemented using the client-specific "put" command.

STOU
Short for STOre Uunique, it requests that the file being stored on the server be given a unique filename. The server chooses the unique name for the stored file, and reports the name chosen back to the client. On some FTP clients, this ability is enabled using the client-specific "sunique" command.

SYST

TYPE

USER
An FTP client uses this command to inform the server of the name of the user requesting an FTP session.

XCUP
This is an X-variant of the CDUP command, and has the same functionality.

XCWD
This is an X-variant of the CWD command, and has the same functionality.

XMKD
This is an X-variant of the MKD command, and has the same functionality.

XPWD
This is an X-variant of the PWD command, and has the same functionality.

XRMD
This is an X-variant of the RMD command, and has the same functionality.

Supported SITE commands

CHGRP
Short for CHange GRouP.
Example:
```
    SITE CHGRP ftpgroup script.cgi
```

CHMOD
Short for CHange MODe.
Example:
```
    SITE CHMOD 755 script.cgi
```

HELP

MKDIR
Similar to the MKD command, this SITE can be used to create a directory. It will, unlike MKD, also create any directories in the path that do not exist.
Example:
```
  SITE MKDIR /path/to/some/dir/that/is/not/there/
```
Supported by the mod_site_misc module.

RMDIR
Similar to the RMD command, this SITE can be used to remove a directory. It will, unlike RMD, also delete any files in the directory.
Example:
```
  SITE RMDIR /path/to/some/dir/with/files/
```
Supported by the mod_site_misc module.

SYMLINK
Used to create a symbolic link (a.k.a. a symlink) from the source path (src) to the destination path (dest).
Example:
```
  SITE SYMLINK src dest
```
Supported by the mod_site_misc module.

UTIME
Used to update the access and modification timestamps on a file.
Example:
```
  SITE UTIME 200412312359 /path/to/some/file.txt
```
Supported by the mod_site_misc module.

Unsupported FTP Commands

ACCT
Short for ACCounT

MACB
Short for MACintosh Binary. This command is not defined in any RFC, and is something of a hack added by Apple in order to support transfers of the resource forks of Mac files.

REIN

SMNT

STRU
Short for STRUcture. proftpd only supports a STRU parameter of type F (for "file"), and so does not support this command.

Frequently Asked Questions

Question: I can use the RNFR and RNTO commands to move a file, even across different disks/mount points. And I can use RNFR/RNTO to move a directory, but I cannot move a directory across different disks/mount points. Is this a bug?
Answer: No, it is not a bug. Why not? Ultimately, it is because the FTP specifications do not guarantee (or even discuss) that an FTP implementation must support renaming of directories across mount points.

ProFTPD implements the RNFR/RNTO functionality by using the rename(2) system call. And rename(2) is documented to not work across mount points.

"But then why does it work when I rename a file across mount points?" you ask. Good question. The answer is that for files only, ProFTPD detects the rename(2) error for renaming across mount points, and then copies the file in question to the new location, deleting the old location when the copy completes successfully.

"Great!" you say, "Now do the same thing for directories!" Unfortunately, for directories, the answer is not that simple. Here are some things to consider when copying directories: what if the directory contains sockets, FIFOs, devices, and other irregular file types which cannot be easily copied/moved? Should copying/moving of directories automatically use root privileges in order to preserve the ownership on files that do not belong to the logged-in user? What if the copying/deleting of files fails in the midde: what should then happen to the copied (and remaining) files/directories?

Since there are no easy answers as yet to the above questions, ProFTPD now detects the rename(2) error for renaming across mount points for a directory, and rejects the RNTO command, showing something like:

  RNFR directory
  350 File or directory exists, ready for destination name
  RNTO /other/mount/directory
  550 Rename /other/mount/directory: Is a directory

That "Is a directory" error indicates that ProFTPD cannot rename a directory across the mount points you requested. (That particular error message can, and will, be made more informative.)