12. Uugetty for Dial-In (from the old Serial-HOWTO)

Be aware that you could use mgetty as a (better?) alternative to uugetty. mgetty is newer and more popular than uugetty. See What is getty? for a brief comparison of these 2 gettys.

12.1 Installing getty_ps

Since uugetty is part of getty_ps you'll first have to install getty_ps. If you don't have it, get the latest version from metalab.unc.edu:/pub/Linux/system/serial. In particular, if you want to use high speeds (57600 and 115200 bps), you must get version 2.0.7j or later. You must also have libc 5.x or greater.

By default, getty_ps will be configured to be Linux FSSTND (File System Standard) compliant, which means that the binaries will be in /sbin, and the config files will be named /etc/conf.{uu}getty.ttySN. This is not apparent from the documentation! It will also expect lock files to go in /var/lock. Make sure you have the /var/lock directory.

If you don't want FSSTND compliance, binaries will go in /etc, config files will go in /etc/default/{uu}getty.ttySN, and lock files will go in /usr/spool/uucp. I recommend doing things this way if you are using UUCP, because UUCP will have problems if you move the lock files to where it isn't looking for them.

getty_ps can also use syslogd to log messages. See the man pages for syslogd(1) and syslog.conf(5) for setting up syslogd, if you don't have it running already. Messages are logged with priority LOG_AUTH, errors use LOG_ERR, and debugging uses LOG_DEBUG. If you don't want to use syslogd you can edit tune.h in the getty_ps source files to use a log file for messages instead, namely /var/adm/getty.log by default.

Decide on if you want FSSTND compliance and syslog capability. You can also choose a combination of the two. Edit the Makefile, tune.h and config.h to reflect your decisions. Then compile and install according to the instructions included with the package.

12.2 Setting up uugetty

With uugetty you may dial out with your modem while uugetty is watching the port for logins. The original author of this HOWTO said to use /dev/cuaN for dial-out (with uugetty running on /dev/ttyN). but others say you must use /dev/ttyN for both dial-in and dial-out ??

uugetty does important lock file checking. Update /etc/gettydefs to include an entry for your modem. When you are done editing /etc/gettydefs, you can verify that the syntax is correct by doing:

linux# getty -c /etc/gettydefs

Modern Modems

If you have a 9600 bps or faster modem with data compression, you can lock your serial port to one speed. For example:

# 115200 fixed speed
F115200# B115200 CS8 # B115200 SANE -ISTRIP HUPCL #@S @L @B login: #F115200

If you have your modem set up to do RTS/CTS hardware flow control, you can add CRTSCTS to the entries:

# 115200 fixed speed with hardware flow control
F115200# B115200 CS8 CRTSCTS # B115200 SANE -ISTRIP HUPCL CRTSCTS #@S @L @B login: #F115200

Old slow modems

If you have a slow modem (under 9600 bps) Then, instead of one line for a single speed, your need several lines to try a number of speeds. Note the these lines are linked to each other by the last "word" in the line such as #38400. Blank lines are needed between each entry.

# Modem entries
115200# B115200 CS8 # B115200 SANE -ISTRIP HUPCL #@S @L @B login: #57600

57600# B57600 CS8 # B57600 SANE -ISTRIP HUPCL #@S @L @B login: #38400

38400# B38400 CS8 # B38400 SANE -ISTRIP HUPCL #@S @L @B login: #19200

19200# B19200 CS8 # B19200 SANE -ISTRIP HUPCL #@S @L @B login: #9600

9600# B9600 CS8 # B9600 SANE -ISTRIP HUPCL #@S @L @B login: #2400

2400# B2400 CS8 # B2400 SANE -ISTRIP HUPCL #@S @L @B login: #115200

Login Banner

If you want, you can make uugetty print interesting things in the login banner. In Greg's examples, he has the system name, the serial line, and the current bps rate. You can add other things:

       @B    The current (evaluated at the time the @B is seen) bps rate.
       @D    The current date, in MM/DD/YY.
       @L    The serial line to which uugetty is attached.
       @S    The system name.
       @T    The current time, in HH:MM:SS (24-hour).
       @U    The number of currently signed-on users.  This is  a
             count of the number of entries in the /etc/utmp file
             that have a non-null ut_name field.
       @V    The value of VERSION, as given in the defaults file.
       To display a single '@' character, use either '\@' or '@@'.

12.3 Customizing uugetty

There are lots of parameters you can tweak for each port you have. These are implemented in separate config files for each port. The file /etc/conf.uugetty will be used by all instances of uugetty, and /etc/conf.uugetty.ttySN will only be used by that one port. Sample default config files can be found with the getty_ps source files, which come with most Linux distributions. Due to space concerns, they are not listed here. Note that if you are using older versions of uugetty (older than 2.0.7e), or aren't using FSSTND, then the default file will be /etc/default/uugetty.ttySN. Greg's /etc/conf.uugetty.ttyS3 looked like this:

# sample uugetty configuration file for a Hayes compatible modem to allow
# incoming modem connections
#
# alternate lock file to check... if this lock file exists, then uugetty is
# restarted so that the modem is re-initialized
ALTLOCK=cua3
ALTLINE=cua3
# line to initialize
INITLINE=cua3
# timeout to disconnect if idle...
TIMEOUT=60
# modem initialization string... 
# format: <expect> <send> ... (chat sequence)
INIT="" AT\r OK\r\n
WAITFOR=RING
CONNECT="" ATA\r CONNECT\s\A
# this line sets the time to delay before sending the login banner
DELAY=1
#DEBUG=010

Add the following line to your /etc/inittab, so that uugetty is run on your serial port, substituting in the correct information for your environment - run-levels (2345 or 345, etc.) config file location, port, speed, and default terminal type:

S3:2345:respawn:/sbin/uugetty -d /etc/default/uugetty.ttyS3 ttyS3 F115200 vt100

linux# init q 

Now Linux will be watching your serial port for connections. Dial in from another machine and login to you Linux system.

uugetty has a lot more options, see the man page for uugetty) (often just called getty) for a full description. Among other things there is a scheduling feature, and a ringback feature.