Linux notes: Introduction, Login

Q1) What is an operating system?

An operating system is a low-level software that schedules tasks, allocates storage, and handles interfaces to peripheral hardware such as printers, disk drives, the screen, keyboard, and mouse.

Q2) What are the main parts of an operating system?

An operating system has two main parts:

  1. Kernel
  2. System Programs
Q3) What is Kernel?

The kernel allocates machine resources, including memory, disk space, and CPU cycles, to all other programs that run on the computer.

Q4) What are system programs?

The system programs perform high-level housekeeping tasks often acting as servers in a client/server relationship.

Linux is a kernel.

Logging into system

  • To login in on a terminal, terminal emulator, or other text-based device enter your username and password
  • If you are using terminal enter the login command
$ login 
login : <username>
Password: <password>
  • If the login prompt does not appear, then try pressing ctrl+q

Login from workstation

  • Use ssh/telnet command to login from workstation
  • Login using ssh program:
$ ssh <username>@<IP address>
Password: <password>
<remote $>
  • Login using telnet program:
$ telnet <IP address>
username: <username>
Password: <password>
<remote $>
  • To login to any system, from workstation, we require three things:
    • IP Address or Domain name
    • Username
    • Password
  • Make sure the system you want to log into is running ssh/telnet server
  • After logging in you may get one or two short messages called message of the day (motd) and issue. These messages generally identify the version of Linux that is running, along with local messages placed in either the /etc/motd or /etc/issue file.

TERM

  • TERM is a shell variable that is used to define display settings of terminal
  • If after logging in, the display is not proper, then you have to check your TERM value
$ echo $TERM
xterm-256color
Q5) What is the difference between ssh and telnet?

ssh is secure. The ssh utility encrypts all information it sends over the network.

telnet is not secure. It sends your username and password over the network in cleartext when you log in, allowing someone to capture your login information and access your system.

Q) What are some common reasons that Login fails?
  • You are logging into wrong machine
  • Login is case sensitive
  • Make sure your login credentials (username and password) are correct
Q) How to Logout from a system?

Use the CTRL+D or type the “exit” command.

Q) How many virtual consoles can be run on a Linux system?

63

Q) How to switch between different virtual consoles?

Press down the CTRL+ALT key and simultaneously the function key of the console number. For instance, if you want to open the 5th virtual console, you should hod down CTRL+ALT+F5.

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