You can access up to 6 consoles by default, with the keystrokes Ctrl-Alt-F1 to Ctrl-Alt-F6. These are running getty on tty1 to tty6. From within one of these consoles, to change to another one, use either Ctrl-Alt-F/num/ or Alt-F/num/. X is running on Alt-F7.
Debian uses agetty (in the util-linux package).
Uses
If you are updating packages, including libraries, which X uses then it is best to use apt-get or aptitude from a console, then restart X.
Troubleshooting
If the above keystrokes don't work, dpkg-reconfigure console-data often fixes the keyboard (in /etc/console).
Failing that, check in /etc/inittab:
# The default runlevel is 2: id:2:initdefault: ...
# tty1 will run for runlevels 1 to 5; # tty2 to tty6 will run for runlevels 1 to 3: 1:12345:respawn:/sbin/getty 38400 tty1 2:123:respawn:/sbin/getty 38400 tty2 3:123:respawn:/sbin/getty 38400 tty3 4:123:respawn:/sbin/getty 38400 tty4 5:123:respawn:/sbin/getty 38400 tty5 6:123:respawn:/sbin/getty 38400 tty6
Options
Alternatives using less memory: mingetty or fgetty
Q: Is it possible to set up terminals that will boot to individual colors? ie tty1 cyan, tty2 green, tty3 yellow. etc...etc. I know the command setterm -foreground cyan -bold -store, but this all lost when I reboot. Any ideas?
A: I'd try putting the correct options in /etc/inittab. One way: create a new issue (e.g. /etc/issue2) for each virtual console and put the string that setterm outputs in that, and then use the -f option of getty to point to those (in /etc/inittab. If you want it to take effect before the next reboot use telinit q to re-read inittab.) (tested, works for me.)
Best way (probably) is use the -I option to getty. Take output from setterm, replace Esc chars with "\033". As so:
2:2345:respawn:/sbin/getty -I "\033[36m\033[1m\033["8"]" 38400 tty2
(remember telinit q afterwards).