Logging in and Logging out of Linux - R.D.Sivakumar
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This document discusses logging in and logging out of Linux systems. It explains that Linux allows multiple users to work simultaneously, each with their own login and password. When connecting, the user enters their login name at the login prompt and then enters their password at the password prompt. To logout, the user enters the "exit" or "logout" command. The document also describes how a user can change their password using the "passwd" command, by entering their current password twice and then entering a new password twice for verification.
![Logging in/ Logging out of Linux
Linux systems allow many users to work simultaneously. A user normally
works at a user terminal. You have to establish connection to the Linux system,
the system after showing some information; will show Login prompt(prompt is a
helping message), which is the location where you enter your user name. Your
Login name is nothing but user (your) name. You need not be frightened by the
word Login, which simply means user here.
When you connect to the Linux system, you will be asked to enter your Login
name at the Login prompt, you have to enter your Login name and you will be
shown the
Password prompt. You have to enter your password.
To keep your password a secret, the Linux system will not display your
password. The system compares these two items with the system files. If the
match is not found, then you should enter these two items. Ofcourse, if the match
is found you will be shown the following prompt;
[ilamathi@localhost ilamathi] $](https://image.slidesharecdn.com/linux3-210810080120/85/Logging-in-and-Logging-out-of-Linux-R-D-Sivakumar-2-320.jpg)
![Logging in/ Logging out of Linux
[ilamathi@localhost ilamathi] $
Here you assume your login name is ilamathi. You should be careful about the
lower case and upper case letters because the system is case sensitive. The
verification process does not allow any unauthorized person to access any of your
directories or files. Normally, not necessarily, the name of the user is the Login
name.
The Home Directory is assigned to the user when he/she enters into the system
for the first time, by the System Administrator ( SA ). You will learn about SA
later.
Logout Process
Entering exit or logout at the command prompt will end your current Linux
session then the system displays the Login prompt on the screen for other users.](https://image.slidesharecdn.com/linux3-210810080120/85/Logging-in-and-Logging-out-of-Linux-R-D-Sivakumar-3-320.jpg)
![Logging in/ Logging out of Linux
Changing the password
Suppose you have an uneasy feeling that someone knows your password. Then you
have to spend sleepless nights. The Linux operating system has its own method of
solving your problem. It allows you to change your password. A user can change
his/her password with the passwd command. The steps followed by the user, ilamathi,
to change her password are depicted below. The actual prompt is similar to the one
shown here.
Example:
[ilamathi@localhost ilamathi]$ passwd ( the user enters his/her password)
Changing password for ilamathi (current ) password: (User enters the current
password)
New password: (User enters the new passeord)
Retype new password: (User re-enters the new password)
passwd: all authentication tokens updated successfully
[ilamathi@localhost ilamathi]$ _
The passwd command asks for the old password. This command is essential to check
up the authenticity of the user. Again the system demands that the user should make up
his/her mind about the new password. That is why it asks the new password twice.](https://image.slidesharecdn.com/linux3-210810080120/85/Logging-in-and-Logging-out-of-Linux-R-D-Sivakumar-4-320.jpg)
![Logging in/ Logging out of Linux
Example:
[ilamathi@localhost ilamathi]$ passwd
Changing password for ilamathi
( current ) password:(User enters the current password)
New passwd:(User enters the new passeord)
Retype new password: (User misspells the new password)
Sorry, passwords do not match
New password:
If you commit a mistake in typing the current password (that is the password that
you want to change) then you may not be an authenticated user. So, there is a
suspicion that you are trying to change someone else’s password. Therefore you will
not be allowed to change the password. If two entries of the new password do not
match then the system is in a dilemma. The system does not know which is to be
accepted. So, your new password is outrightly rejected. Hence you should be careful
about the old as well as the new passwords.](https://image.slidesharecdn.com/linux3-210810080120/85/Logging-in-and-Logging-out-of-Linux-R-D-Sivakumar-5-320.jpg)
Logging in and Logging out of Linux - R.D.Sivakumar
- 1. R.D.SIVAKUMAR, M.Sc.,M.Phil.,M.Tech., Assistant Professor of Computer Science & Assistant Professor and Head, Department of M.Com.(CA), Ayya Nadar Janaki Ammal College, Sivakasi – 626 124. Mobile: 099440-42243 e-mail : sivamsccsit@gmail.com website: www.rdsivakumar.blogspot.in Logging in/ Logging out of Linux
- 2. Logging in/ Logging out of Linux Linux systems allow many users to work simultaneously. A user normally works at a user terminal. You have to establish connection to the Linux system, the system after showing some information; will show Login prompt(prompt is a helping message), which is the location where you enter your user name. Your Login name is nothing but user (your) name. You need not be frightened by the word Login, which simply means user here. When you connect to the Linux system, you will be asked to enter your Login name at the Login prompt, you have to enter your Login name and you will be shown the Password prompt. You have to enter your password. To keep your password a secret, the Linux system will not display your password. The system compares these two items with the system files. If the match is not found, then you should enter these two items. Ofcourse, if the match is found you will be shown the following prompt; [ilamathi@localhost ilamathi] $
- 3. Logging in/ Logging out of Linux [ilamathi@localhost ilamathi] $ Here you assume your login name is ilamathi. You should be careful about the lower case and upper case letters because the system is case sensitive. The verification process does not allow any unauthorized person to access any of your directories or files. Normally, not necessarily, the name of the user is the Login name. The Home Directory is assigned to the user when he/she enters into the system for the first time, by the System Administrator ( SA ). You will learn about SA later. Logout Process Entering exit or logout at the command prompt will end your current Linux session then the system displays the Login prompt on the screen for other users.
- 4. Logging in/ Logging out of Linux Changing the password Suppose you have an uneasy feeling that someone knows your password. Then you have to spend sleepless nights. The Linux operating system has its own method of solving your problem. It allows you to change your password. A user can change his/her password with the passwd command. The steps followed by the user, ilamathi, to change her password are depicted below. The actual prompt is similar to the one shown here. Example: [ilamathi@localhost ilamathi]$ passwd ( the user enters his/her password) Changing password for ilamathi (current ) password: (User enters the current password) New password: (User enters the new passeord) Retype new password: (User re-enters the new password) passwd: all authentication tokens updated successfully [ilamathi@localhost ilamathi]$ _ The passwd command asks for the old password. This command is essential to check up the authenticity of the user. Again the system demands that the user should make up his/her mind about the new password. That is why it asks the new password twice.
- 5. Logging in/ Logging out of Linux Example: [ilamathi@localhost ilamathi]$ passwd Changing password for ilamathi ( current ) password:(User enters the current password) New passwd:(User enters the new passeord) Retype new password: (User misspells the new password) Sorry, passwords do not match New password: If you commit a mistake in typing the current password (that is the password that you want to change) then you may not be an authenticated user. So, there is a suspicion that you are trying to change someone else’s password. Therefore you will not be allowed to change the password. If two entries of the new password do not match then the system is in a dilemma. The system does not know which is to be accepted. So, your new password is outrightly rejected. Hence you should be careful about the old as well as the new passwords.
- 6. Logging in/ Logging out of Linux Some of the rules for changing the password: The password should not be less than six characters in length. When changing a password, the new password should differ from the old password by at least three positions The password should be different from the user’s Login name. The new password cannot be the same as the old password. It is ridiculous to change the password with same password. Since the SA can execute control over the entire system, SA can change the password of any user of the Linux system.