introduction to the linux environment
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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! - PowerPoint PPT PresentationTRANSCRIPT
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?
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 Commands
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?
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 Commands
Typecd /
And pwd
We are back at root (/)Type
cd usr/localAnd
pwdWe are back at /usr/local
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 Commands
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
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)
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!