"The Linux Gazette...making Linux just a little more fun!"

FTP Daemon: Special Requirements

From William Dawson on Tue, 12 Oct 1999

Hello, Mr. Dennis.

I'm in desperate need of help...I'm down to only one functioning nerve...

After much brain-strain and (I don't mind saying) heavy persistence, I finally found the right man pages to tell me how to change the port that ftp listens on, and other things of the like. My problem now is that can't seem to figure out how to set the maximum number of simultaneous ftp users (limit<class><n><times><message_file> seems not to work in the ftpaccess file...<times> format is of particular concern). Also, how do I limit users to only one ftp connection (login) at a time?

If you can help me out with any of this, I would be eternally grateful.

Are you sure you're running WU-ftpd? Other FTP daemons don't necessary read the /etc/ftpaccess file.

If you're using the BSD ftpd (possibly reported from OpenBSD) then it would ignore /etc/ftpaccess (unless then changed it). If you're using ProFTPd, BeroFTPd, or ncftpd then you'd use different files to configure each of them.

Also are you SURE you want to change the port on which you are running your FTP daemon. I could see cases where you might want your ftpd to selectively bind to some interfaces or IP aliases and to ignore others (which means that you can support FTP virtual hosting, among other things). However, running it on a different port seems like a bad idea since many FTP clients (especially those in MS Windows) don't offer options to connect to non-standard ports.

The limit directive in the WU-FTPD doesn't give you a way to limit the number of concurrent connections PER USER. (At least I don't remember such a thing). It's intended to limit the total number of connections for each "class" of users (mostly to insure that anonymous users don't bog the machine down so much that your own employees, students, etc can't access the system).

I think you might want to look at the documentation for the ProFTPd and/or the ncftpd packages before you fight too much with your current FTP daemon. Please note that ProFTPd has been hit with a couple of security exploits recently --- so make sure you get the most recent version (with bug fixes) and you what the 'net for alerts. There may be more bugs waiting to be discovered in this package. (Of course that's true in every software package. But some have a better reputation than others; and write now WU-FTPD and ProFTPd are at the high end of that reputation scale.).

ncftpd is not free software. However, Mike Gleason, its author has a good reputation in the open source community. His ncftp CLIENT is free and is one of the best.

You can find these at:

NcFTP Software

http://www.ncftp.com

ProFTPd

http://www.proftpd.org

WU-ftpd

http://www.wu-ftpd.org

BeroFTPd

http://apps.freshmeat.net/download/895008043

pftpd

http://apps.freshmeat.net/download/918313631

I tossed in links to a couple of other FTP daemons that might be interesting.

Copyright © 1999, James T. Dennis
Published in The Linux Gazette Issue 48 December 1999

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