Keyboards, Consoles, and VT Cruising

The first exception to note is that when the X Window System starts, it is displayed on the first unused tty—one that doesn't have a getty running on it. Since the first six ttys had gettys running on them, X would, in the example above, start on tty 7. Now we know the solution to the great riddle, “So where is X ?”, when you switch from X to a console. Pressing crtl-alt-f1 in X would switch you to VT 1. If you wanted to get back to X, simply:

The other exception to note is that while you can't run programs on a VT without logging in, you can still send output there. As a simple experiment try the following:

$ echo "This is a test" > /dev/tty7

Switching to VT 7, you'll see the words “This is a test” displayed. This ability becomes useful with system logging. Without going into an exhaustive discussion of system logging and configuration, it is worth noting that the output of all logging facilities can be “dumped” to an unused VT which allows quick perusal for events such as logins, kernel messages, mail logging, etc. To do this simply add the following line to the /etc/syslog.conf file (after logging in as root):

# this one will log ALL messages to the
#/dev/tty9 terminal since this is an unused
# terminal at the moment. This way, we
# don't need to hang a getty on it or take up
# a lot of system resources.
*.*                     /dev/tty9

Once you've added this stanza to /etc/syslog.conf, you'll need to either kill and restart the syslog daemon or else send it the HUP (hang up) signal. Since this latter method is fairly easy let's do it:

$ ps -x | grep syslog
28  ?  S     0:01 /usr/sbin/syslogd

will output the PID (process ID number) of the syslog daemon which in this case is 28. Now, just type in:

$ kill -HUP 28

in which 28 is the PID number. The syslog daemon will re-read its initialization files. From here on, all logging that occurs, regardless of its source, will be output to tty9 (or whichever tty device you specify).

Switching to VT 9 you might see something like the following:

Jul  1 10:11:37 FiskHaus kernel: Max size:342694   Log zone size:2048
Jul  1 10:11:38 FiskHaus kernel: First datazone:68   Root inode number 139264
Jul  1 10:11:38 FiskHaus kernel: ISO9660 Extensions: RRIP_1991A
Jul  1 12:21:50 FiskHaus login: ROOT LOGIN ON tty2
Jul  1 17:26:56 FiskHaus login: 1 LOGIN FAILURE ON tty5, fiskjm

The first three lines represent kernel messages that occur when a CD is mounted. Root logins are noted by the login program as well as login failures—in this last case I purposely entered an incorrect password.

The value of all of this logging may not be immediately evident, but if you've ever noticed your machine thrashing about and swapping like crazy, or, while on-line, your hard drive lights begin to light up when you're not doing anything—a quick switch to VT 9 can often give you an idea about what's going on. These instructions should get you started. The manual pages for loadkeys, showkey and keytables have much more complete technical descriptions of key mapping. Also, the kbd package comes with a good deal of helpful documentation in its /doc subdirectory. And finally, don't forget the Keyboard-HOWTO which can be found among the growing number of Linux HOWTOs http://www.ssc.com/linux/howto.html).