Setting Up UUCP

UUCP is actually a suite of programs to do very specific tasks. For example, uucp itself is used for copying files between nodes (the machines connected via UUCP) and uux is used for executing programs on another node. Programs exist for all kinds of maintenance, like logfile-trimming and spool-checking. For my purposes (and the purposes of this article), the most important programs are uucico and uuxqt. uucico actually places the phone call and sets up file transfers, while uuxqt tells the other machine what program needs to be run for proper handling of the files.

The following sequence of events is typical:

Typing uucico -s sloth causes uucico to look up sloth in config. Seeing it should use serial1 to connect to sloth, it looks in port and sees that serial1 is the modem, which is activated by the dialer entry. Peeking at this entry in dial, uucico initializes the modem and calls the number specified in sys. When the CONNECT string is received, it executes the chat script from sys and logs into sloth.

When the login procedure is complete, perrin is in “master” mode and sloth is in “slave” mode. Files to be uploaded will be in the spool directory /var/spool/uucp/sloth/D./filename. If these files exist, perrin will upload them with instructions for the slave. The instruction files will be in /var/spool/news/uucp/sloth/C./filename. When the transfer is complete, the master and slave exchange roles, with perrin now receiving any files spooled on sloth, as well as execution instructions. When both sides have transferred all the necessary files, the connection is terminated. Logging is done in /var/log/uucp, so take a look in there for an exhaustive roster of an average session's work.

When the connection is broken, the second important UUCP program is fired up: uuxqt. uuxqt looks in the UUCP spool directory for execution requests and (if permitted) executes them. For example, files consisting of mail messages must be delivered and news postings must be moved into the news spool. By default, UUCP permits only two local programs, rmail and rnews, to be executed, which not-so-coincidentally accomplish the tasks just mentioned.

With UUCP configured and tested, it's now time to set up the transfer of mail and news.

For mail transport and delivery, the two most obvious choices are sendmail and smail. I have read that for small sites the two are roughly equivalent in configuration difficulty, but I've also seen O'Reilly's sendmail book. Nothing that massive could possibly be required for my little project. Accordingly, I chose smail. The current release is v3.1.29—while not part of Red Hat's distribution, some kindly soul has made an RPM available in the /pub/contrib directory at ftp.redhat.com.

After looking at a full source tree for smail, I chickened out and grabbed a precompiled rpm from Red Hat's /pub/contrib directory, then installed it:

rpm -i smail-3.1.29.1-6.i386.rpm

Two links to smail are needed: usr/bin/rmail and /usr/sbin/sendmail. The former is invoked when mail comes in for delivery via UUCP; the latter is often hardcoded into mail user agents, such as elm. To create these links, use the following commands:

ln -s /path_to_smail/smail  /usr/bin/rmail
ln -s /path_to_smail/smail  /usr/sbin/sendmail

Note that rmail, or a link to it, must be placed in the command-path specified in etc/uucp/sys or this will fail. Your ISP might have permission to run rmail, but if he can't find it then he'll get all sorts of error messages in his UUCP logs and might just send you a nasty e-mail message. Of course, if you've already arranged for mail to be sent via UUCP, this will backfire on the ISP, and you will quickly find yourself less than popular. Or so I hear.

The main configuration file for smail is etc/smail/config. For a site which will be doing all its mailing through a UUCP link, this is a remarkably simple file, especially since the smail package comes with very nice sample files in etc/smail/config.linux. Of the four files smail will use, I had to modify only config for my particular setup:

#  /etc/smail/config
smart_path=sloth
smart_transport=uux
visible_name=swcp.com
uucp_name=perrin.swcp.com

The smart_path entry is the UUCP name of your ISP's machine. This will match the system name in /etc/uucp/sys. Any non-local mail address will be shipped off to this machine for DNS resolution and delivery. Specifying uux as the transport agent will cause any outgoing mail messages to be queued in the UUCP spool to await the next UUCP connection. I will return to this when I discuss the other configuration files for smail.

The visible_name entry identifies your smail domain. If you have registered your UUCP name, append :uucp to this entry. In many cases, this is unnecessary. Using my system as an example, the .swcp.com portion is guaranteed by the InterNIC (and my ISP's hard-earned dollars) to be unique. Therefore, the only machines which could have already taken perrin would be connected to my ISP, who would notify me of a conflict.

The uucp_name entry is (surprise) your system's UUCP name. By default, smail will generate return paths from the hostname command, in my case perrin. Since I have not registered perrin, someone else might. Without this entry, any mail returned to perrin will go to that other machine. By specifying a fully qualified domain name, I am guaranteed (because of the way DNS and UUCP addressing are resolved) the message will go first to swcp.com, which will recognize perrin as my UUCP account. For a machine named “perrin”, this is a negligible concern, but a more common name, e.g., “darkstar”, might cause problems.