Introduction to the Linux Environment

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Introduction to the Linux Environment

• Brian E. Brzezicki

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First things first

• Log in to your linux machine using
• Username student
• Password student01

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Terminal!

• Next Linux is VERY text based environment, so
  lets get used to the Terminal!
• Click on Applications-gtAccessories-gtTerminal
  until you get this! (next slide)

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Terminal
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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!

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Basics of the Linux File System structure
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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)

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Linux File System
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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

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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

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Lets look around

• Open up your terminal windows now and lets look
  at some programs used to navigate the filesystem
  in unix

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File System Commands

• cd change directory
• pwd print working directory
• In your terminal type
• cd /usr/local
• Now type
• pwd
• What is the response?

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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.

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File System Commands

• You can add multiple .. together
• For example. Lets 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?

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File System Commands

• Right Ill 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, lets move back to the root
  directory (/)
• Type
• cd /
• And verify with
• pwd

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File System Commands

• So now that we are at / lets 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?

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File System Commands

• Now lets move into local
• Type
• cd local
• And
• pwd
• Where are we now?
• Lets start again and do it in only one step

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File System Commands

• Type
• cd /
• And
• pwd
• We are back at root (/)
• Type
• cd usr/local
• And
• pwd
• We are back at /usr/local

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File System Commands

• OK now that we can move around lets learn
  another important linux command
• ls list directory contents
• cd /usr/local
• ls
• What is the response?

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File System Commands

• How about
• ls l
• (next page for results explain the entries)

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• root_at_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 1403 share
• drwxr-xr-x 2 root root 4096 Mar 9 2009 src

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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)

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Using ls

• Do a quick exercise
• cd /home
• pwd
• ls
• cd student
• pwd
• ls -latr

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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

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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

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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

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More useful commands (set 4)

• chmod change file permissions
• chmod username filename
• example
• chmod student /tmp/file
• chown change file owner
• chown urwx,grwx,orwx filename
• u-rwx,g-rwx,o-rwx

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Example of chmod

• cd /tmp
• touch file
• ls l file
• -rw-r--r-- 1 root root 0 Apr 21 1541 file
• chmod ux,gx,o-r file
• ls l file
• -rwxr-x--- 1 root root 0 Apr 21 1541 file
• chmod urwx,grwx,orwx file
• ls l file
• -rwxrwxrwx 1 root root 0 Apr 21 1541 file

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More useful commands (set 5)

• grep search a file for a specific line of text
• grep root /etc/passwd
• root_at_linux1 grep root /etc/passwd
• rootx00root/root/bin/bash
• operatorx110operator/root/sbin/nologin
• locate search the system for a specific filename
• locate ssh_config
• root_at_linux1 locate ssh_config
• /etc/ssh/ssh_config
• /usr/share/man/man5/ssh_config.5.gz

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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_at_linux1 cat /etc/passwd grep root
• rootx00root/root/bin/bash
• operatorx110operator/root/sbin/nologin

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Redirect operators

• Like with PIPE in Linux you can redirect the
  output of one command to a file (gt), or redirect
  the contents of a file to be the input of a
  program (lt)
• Example
• grep root /etc/passwd gt /tmp/grep_results.txt
• or
• grep root lt /etc/passwd

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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

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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

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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. Id suggest vi
• So lets look at vi in the next couple slides

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vi

• First lets copy a file that we can edit
• cp /usr/share/dict/words /tmp/words.txt
• Now lets open this with vi
• vi /tmp/words.txt

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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)

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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

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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

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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

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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

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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 youll want to do.

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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!

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Labs! Lets get some hands on practice now!