introduction to the linux environment

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!Click on Applications->Accessories->Terminal

until you get this! (next slide)

Terminal

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!

Basics of the Linux File System structure

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)

Linux File System

Entering CommandsWhen 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 directorycd /etc

cat passwd

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 commandcat /etc/passwd

Or

cat ../passwd

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

cd – change directory

pwd – print working directory

In your terminal type

cd /usr/local

Now type

pwd

What is the response?


Now type

cd . .

and

pwd

Now what is the response?

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


You can add multiple “..” togetherFor example. Let’s get back to /usr/localUse the command

cd /usr/localType

pwdTo verify your in “/usr/local”What do you think will happen if I type

cd ../..And type pwd?

File System CommandsRight 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 CommandsSo 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 areType

cd usrAnd

pwdWhere are we now?


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


Typecd /

And pwd

We are back at root (/)Type

cd usr/localAnd

pwdWe are back at /usr/local


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?


How about

ls –l

(next page for results… explain the entries)

[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

• 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 lsDo a quick exercise

cd /home

pwd

ls

cd student

pwd

ls -latr


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)

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)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)

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

cd /tmptouch filels –l file

-rw-r--r-- 1 root root 0 Apr 21 15:41 filechmod u+x,g+x,o-r filels –l file

-rwxr-x--- 1 root root 0 Apr 21 15:41 filechmod u+rwx,g+rwx,o+rwx filels –l file

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

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 (|)

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

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 operatorsOften in Linux you will want to see what

processes are running and possibly manipulate them you do this will the commands

psps –ef

killkill -9 pidkill –TERM pid

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

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

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

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

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 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

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

Some edit mode commandsx delete the current characterkdd delete the entire current lineYou can add a number before either of these

commands to do that command multiple times

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 fileWhen 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 pagesLinux 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 typeman commandExampleman lsYou can even do a man on the man pagesman manYou will learn to love the man pages!

Labs! Let’s get some hands on practice now!

introduction to the linux environment

Documents