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TTY in linux and how to use it



Ok, how about we start with what is TTY.It stands for “teletypewriter.”


What can tty tell us.
In Linux, there is a pseudo-teletype multiplexor which handles the connections from all of the terminal window pseudo-teletypes (PTS). The multiplexor is the master, and the PTS are the "slaves". The multiplexor is addressed by the kernel through the device file located at /dev/ptmx.



The tty command will print the name of the device file that your pseudo-teletype slave is using to interface to the master. And that, effectively, is the number of your terminal window.

The output shows that we are connected to to the device file at /dev/pts/4.

Our terminal window, which is a software emulation of a teletype (TTY), is interfaced to the pseudo-teletype multiplexor as a pseudo-teletype (PTS). And it happens to be number four.For the number at the end shows that.

The Silent Option.

The -s (silent) option causes tty to generate no output.

This is how it will look on your terminal


It does is produce an exit value, however:

  • 0: if standard input is coming from a TTY device, emulated or physical.
  • 1: if standard input is not coming from a TTY device.
  • 2: Syntax error, incorrect command line parameters were used.
  • 3: A write error has occurred.

The who Command

Other commands can reveal your TTY number. The who command will list information for all logged in users, including yourself.


User root is shown as connected to “:1”.

This represents the screen and keyboard physically connected to the computer. Even though the screen and keyboard are hardware devices, they are still connected to the multiplexor through a device file. tty reveals that it is /dev/pts/4.


Accessing a TTY

You can access a full-screen TTY session by holding down the Ctrl+Alt keys, and pressing one of the function keys.

Ctrl+Alt+F4 will bring up the login prompt of tty4.

If you log in and issue the tty command, you’ll see you are connected to /dev/tty4.

This isn’t a pseudo-teletype (emulated in software); it is a virtual teletype (emulated in hardware). It is using the screen and keyboard connected to your computer, to emulate a virtual teletype like the DEC VT100 used to do.

You can use function keys Ctrl+Alt with function keys F3 to F6 and have four TTY sessions open if you choose. For example, you could be logged into tty3 and press Ctrl+Alt+F6 to go to tty6.

To get back to your graphical desktop environment(GUI), press Ctrl+Alt+F2.

At one time, Ctrl+Alt+F1 through to Ctrl+Alt+F6 would open up the full-screen TTY consoles, and Ctrl+Alt+F7 would return you to your graphical desktop environment. If you are running an older Linux distribution, this might be how your system behaves.

This was tested on the latest release of Ubuntu, Kali Linux, Manjaro, Fedora, Arch and they all behaved like this:

  1. Ctrl+Alt+F1: Returns you to the graphical desktop environment log in screen.
  2. Ctrl+Alt+F2: Returns you to the graphical desktop environment.
  3. Ctrl+Alt+F3: Opens TTY 3.
  4. Ctrl+Alt+F4: Opens TTY 4.
  5. Ctrl+Alt+F5: Opens TTY 5.
  6. Ctrl+Alt+F6: Opens TTY 6.
Having access to these full-screen consoles allows people using command-line only installations of Linux—and many Linux servers are configured this way— to have multiple consoles available.


Linux users having bieng able too access these full-screen consoles using command-line only, they are able to configure linux servers and having multiple consoles available.



The tty command gets its name from a device from the late 1800s, appeared in Unix in 1971, and is part of Linux and Unix-like operating systems to this day.

Comments

  1. Irene Nafula29 May 2020 at 09:24

    Daaaaamn, I didn't even know it existed. Great Job

    ReplyDelete

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