2.3. Consoles, terminals and shells

Consoles: Consoles and Virtual Consoles provides input and output with a computer using serial communication. Initially console was a physical device containing a terminal with a monitor and keyboard.
Terminal: A terminal provides text input/output environment that can be used to interact with a console (monitor or keyboard) or transmitted using serial communication. Initially a terminal was a electronic device connected to a microcomputer or mainframe that take input from a keyboard and output to a text mode screen. Terminals or ttys are provided by the kernel. Example of terminal emulators; tmux, ssh, st.
Shell: Shell are command line interpreter that a terminal runs. Shells also manage foreground and background processes. Example of shells dash and bash.

Content of /etc/inittab shows layout organization and default run level and ttys;

        #
        # /etc/inittab: system runlevel description
        #

        # Runlevels:
        #  0	Halt
        #  1(S)	Single-user
        #  2	Multi-user
        #  3-5	Not used
        #  6	Reboot

        id:2:initdefault:

        rc::sysinit:/etc/rc
        rs:S1:wait:/etc/rc.single
        rm:2:wait:/etc/rc.multi
        rd:06:wait:/etc/rc.shutdown
        su:S:wait:/sbin/sulogin -p

        c1:2:respawn:/sbin/agetty --noclear 38400 tty1 linux
        c2:2:respawn:/sbin/agetty 38400 tty2 linux
        c3:2:respawn:/sbin/agetty 38400 tty3 linux
        c4:2:respawn:/sbin/agetty 38400 tty4 linux
        c5:2:respawn:/sbin/agetty 38400 tty5 linux
        c6:2:respawn:/sbin/agetty 38400 tty6 linux
        #s1:2:respawn:/sbin/agetty 38400 ttyS0 vt100

        ca::ctrlaltdel:/sbin/shutdown -t3 -r now

        # End of file

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