A Linux system has up to 63 virtual consoles (character devices with
major number 4 and minor number 1 to 63), usually called
/dev/ttyn with 1 ≤ n ≤ 63. The current
console is also addressed by /dev/console or /dev/tty0, the
character device with major number 4 and minor number 0. The device files
/dev/* are usually created using the script MAKEDEV, or using mknod(1),
usually with mode 0622 and owner root.tty.
Before kernel version 1.1.54 the number of virtual consoles was compiled into
the kernel (in tty.h: #define NR_CONSOLES 8) and could be changed by editing
and recompiling. Since version 1.1.54 virtual consoles are created on the fly,
as soon as they are needed.
Common ways to start a process on a console are: (a) tell init(8) (in
inittab(5)) to start a getty(8) on the console; (b) ask
openvt(1) to start a process on the console; (c) start X - it will find
the first unused console, and display its output there. (There is also the
Common ways to switch consoles are: (a) use Alt+F n or Ctrl+Alt+F
n to switch to console n; AltGr+Fn might bring you to
console n+12 [here Alt and AltGr refer to the left and right Alt keys,
respectively]; (b) use Alt+RightArrow or Alt+LeftArrow to cycle through the
presently allocated consoles; (c) use the program chvt(1). (The key mapping is
user settable, see loadkeys(1); the above mentioned key combinations
are according to the default settings.)
The command deallocvt(1) (formerly disalloc) will free the memory
taken by the screen buffers for consoles that no longer have any associated
Consoles carry a lot of state. I hope to document that some other time. The most
important fact is that the consoles simulate vt100 terminals. In particular, a
console is reset to the initial state by printing the two characters ESC c.
All escape sequences can be found in console_codes(4).