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Introduction to the Linux Environment. Brian E. Brzezicki. First things first. Log in to your linux machine using Username: student Password: student01. Terminal!. Next Linux is VERY text based environment, so let’s get used to the Terminal!

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First things first
First things first

  • Log in to your linux machine using

    • Username: student

    • Password: student01


Terminal
Terminal!

Next Linux is VERY text based environment, so let’s get used to the Terminal!

Click on Applications->Accessories->Terminal until you get this! (next slide)



Terminal2
Terminal

  • Go ahead and close it (click on the “x” in the windows top bar) and open it again… you need to get comfortable with the terminal window!



File system layout
File System Layout

Linux is layed out in a heirarchical manner starting from the “root” ( / ) directory. This is similar to MS Windows except that

  • Linix uses the / as a directory seperator, Windows uses a \

  • Windows has multiple “roots” one for each drive (C:, D: etc). Linux has a single root, separate physical drives are “grafted” onto the tree

    (see image)



Entering commands
Entering Commands

When Entering commands in Linux, most commands take a filename as an option. You can specify a filename as a

  • Full path – Example:

    cat /etc/passwd

  • Relative to your current directory

    cd /etc

    cat passwd


Special relative directories
Special “Relative directories”

  • There are special entries for directories in linux

    . = “this directory”

    .. = “back one directory”

    If I was in the directory /etc/sysconfig, I could read the file /etc/passwd with the following command

    cat /etc/passwd

    Or

    cat ../passwd


Let s look around
Let’s look around

Open up your terminal windows now and let’s look at some programs used to navigate the filesystem in unix


File system commands
File System Commands

cd – change directory

pwd – print working directory

In your terminal type

cd /usr/local

Now type

pwd

What is the response?


File system commands1
File System Commands

Now type

cd . .

and

pwd

Now what is the response?

.. is a useful argument to “cd” that moves you back 1 directory level.


File system commands2
File System Commands

You can add multiple “..” together

For example. Let’s get back to /usr/local

Use the command

cd /usr/local

Type

pwd

To verify your in “/usr/local”

What do you think will happen if I type

cd ../..

And type pwd?


File system commands3
File System Commands

Right I’ll be back at the “root” directory! (/)

Now before we used to get to /usr/local by directly typing the whole path. This is called an absolute path. Because we specified the exact location that we want to go on the system.

But we can also move around using relative paths.

For example, let’s move back to the root directory (/)

Type

cd /

And verify with

pwd


File system commands4
File System Commands

So now that we are at / let’s use “relative” addressing to get to /usr/local

We are going to specific paths relative to where we are

Type

cd usr

And

pwd

Where are we now?


File system commands5
File System Commands

Now let’s move into local

Type

cd local

And

pwd

Where are we now?

Let’s start again and do it in only one step


File system commands6
File System Commands

Type

cd /

And

pwd

We are back at root (/)

Type

cd usr/local

And

pwd

We are back at /usr/local


File system commands7
File System Commands

OK now that we can move around let’s learn another important linux command

ls list directory contents

cd /usr/local

ls

What is the response?


File system commands8
File System Commands

How about

ls –l

(next page for results… explain the entries)


Introduction to the linux environment

[root@linux1 local]# ls -l

total 72

drwxr-xr-x 2 root root 4096 Mar 9 2009 bin

drwxr-xr-x 2 root root 4096 Mar 9 2009 etc

drwxr-xr-x 2 root root 4096 Mar 9 2009 games

drwxr-xr-x 2 root root 4096 Mar 9 2009 include

drwxr-xr-x 2 root root 4096 Mar 9 2009 lib

drwxr-xr-x 2 root root 4096 Mar 9 2009 libexec

drwxr-xr-x 2 root root 4096 Mar 9 2009 sbin

drwxr-xr-x 4 root root 4096 Apr 18 14:03 share

drwxr-xr-x 2 root root 4096 Mar 9 2009 src


Useful ls options
Useful ls options

  • ls –l long listing

  • ls –la long listing, how “hidden” files (file starting with .)

  • ls –lh long listing with easy to read file sizes

  • ls –lt long listing sorted by time and date, most recent first

  • ls –ltr long listing, sorted by time (reverse)


Using ls
Using ls

Do a quick exercise

cd /home

pwd

ls

cd student

pwd

ls -latr


File system commands9
File System Commands

To effectively run Linux you have to have a solid grasp on the filesystem structure and the commands to move around.

Get used to CD, PWD and LS


More useful commands set 2
More useful Commands (set 2)

rm remove file

rm –rf remove directory and everything in that directory recursively

rmdir remove empty directory

mkdir make directory

cp copy a file

mv move a file


More useful commands set 3
More Useful Commands (set 3)

cat show the contents of a file

more show the contents of a file

tail show the last lines of a file

tail -10 shows the last 10 lines of a file

tail -f shows as lines are added to a file

echo displays whatever you type


More useful commands set 4
More useful commands (set 4)

chmod – change file permissions

chmod username filename

example

chmod student /tmp/file

chown – change file owner

chown u+rwx,g+rwx,o+rwx filename

u-rwx,g-rwx,o-rwx


Example of chmod
Example of chmod

cd /tmp

touch file

ls –l file

-rw-r--r-- 1 root root 0 Apr 21 15:41 file

chmod u+x,g+x,o-r file

ls –l file

-rwxr-x--- 1 root root 0 Apr 21 15:41 file

chmod u+rwx,g+rwx,o+rwx file

ls –l file

-rwxrwxrwx 1 root root 0 Apr 21 15:41 file


More useful commands set 5
More useful commands (set 5)

grep search a file for a specific line of text

grep root /etc/passwd

[root@linux1 ~]# grep root /etc/passwd

root:x:0:0:root:/root:/bin/bash

operator:x:11:0:operator:/root:/sbin/nologin

locate search the system for a specific filename

locate ssh_config

[root@linux1 ~]# locate ssh_config

/etc/ssh/ssh_config

/usr/share/man/man5/ssh_config.5.gz


The pipe operator
The PIPE operator (|)

When working with unix, you notice one command usually gives you output.

With linux you can “tie” the output of one program into the “input” of another program with the pipe operator. This is incredibly handy and will be used a lot in your linux administration tasks.

cat /etc/passwd | grep root

[root@linux1 ~]# cat /etc/passwd |grep root

root:x:0:0:root:/root:/bin/bash

operator:x:11:0:operator:/root:/sbin/nologin


Redirect operators
Redirect operators

Like with PIPE in Linux you can redirect the output of one command to a file (>), or redirect the contents of a file to be the input of a program (<)

Example

grep root /etc/passwd > /tmp/grep_results.txt

or

grep root < /etc/passwd


Process operators
Process operators

Often in Linux you will want to see what processes are running and possibly manipulate them you do this will the commands

ps

ps –ef

kill

kill -9 pid

kill –TERM pid


Introduction to the linux environment
su

In unix you generally log in as a “user” account rather than the superuser account

su is a command that lets you switch to a different user and run commands as them

su – root

su - student


Introduction to the linux environment
vi

Linux adminstration is very much about text configuration files. When you have a GUI you can edit these files with a normal editor… however if you want to run Linux you better get used to a text editor. I’d suggest vi

So let’s look at vi in the next couple slides


Introduction to the linux environment
vi

First let’s copy a file that we can edit

cp /usr/share/dict/words /tmp/words.txt

Now let’s open this with vi

vi /tmp/words.txt


Introduction to the linux environment
vi

Now that we are in vi you should understand vi has 2 modes.

Movement mode

Edit mode

When you start you are put into movement mode, an you can move the cursor around using the commands (next page)


Vi movement mode
Vi movement mode

j up a line

k down a line

h left 1 character

l right one character

Use these characters to move around!

Note you can specify a number before the command for example

5j would move you down 5 lines


Vi movement mode1
vi movement mode

You also can go to a certain line number with the command

:XX

Where XX is a line number

Example

Typing

:50 would take me to line 50


Vi edit mode
vi edit mode

Once we are were we want to type or delete in the file we can use “edit mode” commands.

Some edit mode commands

x delete the current characterk

dd delete the entire current line

You can add a number before either of these commands to do that command multiple times


Typing in characters
Typing in characters

So now that we know the basics of deleting characters… how about adding characters?

To do so, we enter insert mode by typing

i enter insert mode

Typing I will let you start entering characters that will go to the left of the current character.

Once in insert mode… type away when your done hit the “Esc” button


Saving the file
Saving the file

When you want to save the file make sure your in normal mode (usually hit esc) then hit

:w save the file but remain open for editing

:wq save the file and quit

There are tons more vi commands, but these are the basics and should provide you with all that you need to do your work. I myself only know a few more than this as these commands make up 95% of anything you’ll want to do.


Man pages
man pages

Linux is much different than windows is that the documentation (useful documentation) for each command is stored on the system and available with man pages.

To view the documentation for a command type

man command

Example

man ls

You can even do a man on the man pages

man man

You will learn to love the man pages!