Tài liệu Logging Into Linux ppt

Lab 10.1.1: Logging Into Linux Estimated Time: 30 minutes Objective In this lab, the student will learn how to boot a Linux computer, log in as the root user, navigate using the Comman

Lab 10.1.1: Logging Into Linux

Estimated Time: 30 minutes

Objective

In this lab, the student will learn how to boot a Linux computer, log in as the root user, navigate using the Command-Line Interface (CLI), and then shut the computer down This lab will cover the following CLI commands:

• su

• man

• ls

Equipment

The following equipment is required for this exercise:

• Computer with Linux Red Hat 7.2 installed

Scenario

The student will boot up the Linux computer and log in using the root user account The student will run Linux in the command line mode and will shut down the system using the Unix-based shutdown command

Turn the computer on and observe the boot process When Linux begins to load, the following screen will be displayed This screen gives the user the option of booting into

the text mode Press the Enter key to bypass this screen, or wait and Linux will

automatically begin to boot (in approximately five seconds)

The boot process may take a few minutes The time will vary according to the speed of the computer As Linux boots, the Linux processes will load The screen should look similar to the following as the Linux system boots up

Do these processes make sense?

After Linux is loaded, the user will be prompted to login During the installation process, the Command-Line Interface (CLI) was set as the default boot The screen below shows

a CLI login prompt

The Linux administrator account is called the root account Type in root and press the

Enter key Be careful when typing because like all UNIX computers, Linux is case

sensitive

Next, type in root’s password:

cisco1

Note: the root account is signified by the # at the prompt

Step 3

It is not a good practice to work as the root user The root user has complete control of the Linux system and can inadvertently delete important files It is better to work as a user that does not have total control and to switch to the root account only when

maintaining or upgrade the system In Linux, it is a simple process to switch users by using the su command

During the installation process two accounts were created One account was for the root account and another for general student use Students will need to ask the instructor for the student account name

At the command prompt, type:

su - studentA1

Note: When root users are switching users they will not be prompted for a password All

other accounts will be prompted for a password

Did the command prompt change? How?

Note: the “–“ after the su command is called a switch When switching users, this switch

will run all associated user scripts To experiment, type exit after logging in as any user other than the root user The user will end up back as the root user Now type:

su studentA1

This time without the “–“ switch What happened? Did the user end up in studentA1’s

home directory?

Make sure to be logged on as a student user To verify this, use the whoami command The whoami command will only display the login name of the current user

At the command prompt type in:

whoami

What were the results?

Step 5

Navigating the Command-Line Interface (CLI) is not difficult if the user knows where to find help In Linux, the man command displays information about CLI commands

For example, to learn about the ls command type in:

man ls

Results of the man ls command

To move around the man screen, click the Enter key to move down

Like DOS, Linux commands may have switches associated with them Note that the ls command uses many switches, -a and –l are the most common

To exit the man command, type the letter:

q The user will return to the CLI

At the CLI, type in the following commands Describe the results after each command is entered:

ls

ls –a

ls –al

How are files hidden in Linux?

Hint: What character does Linux place in front of the file to hide it?

Step 7

In this step, using the shutdown command will turn off the computer Linux, like all NOSs, must complete the shut down process Linux needs time to shutdown so it can put files where they belong Turning off a Linux system quickly can result in files being lost and the corruption of vital configuration settings

To learn about the shutdown command, type in:

From this man page, briefly describe the shutdown command

What does the –r switch do?

What does the –h switch do?

How is the time set with the shutdown command?

Step 8

Only the root user is allowed to shutdown a Linux computer To complete this step, verify that the user is logged in as the root user If not, type:

su – root

If requested, enter the root password

Next, type:

shutdown –h now

Describe the shutdown process

After the shutdown process was complete, did the computer turn off?

Note: With an ATX power supply it will turn the computer off Older AT boxes will not Troubleshooting

IT professionals are frequently called on to troubleshoot Linux log-in problems The following list can be used as a checklist when troubleshooting:

Problem: Cannot log in to the system

• Username or password is misspelled or mistyped Check both the username and password and carefully re-enter this information In both Linux and UNIX, usernames and passwords are case-sensitive, so verify that the password uses the correct case

• Keyboard Caps Lock is on Press the Caps Lock key once, verify that the keyboard

Caps Lock indicator light is off, and try entering the password again

• User has confused username with password Verify that the user is typing his or her

username in the “User name” field, and password in the “Password” field

• When logging in through CLI, some users do not realize that although they do not see anything being entered as they type, the system is taking the input So it is

sometimes common for beginning users to think their machine is frozen at this point Reflection

1 Why is it important to log out or lock the console when leaving it unattended?

2 What are some of the reasons a user may not be able to log in to the server?

3 What advantages does the ability to switch between multiple login terminals provide?