The kernel is the low-level software that manages hardware, multitasks programs, etc.

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1 November Why Use Linux? Save Money Initial purchase and maintenance Resume Linux is used by MANY organizations More choices Tons of Linux operating systems

2 November What is Linux? 1. Contains the Linux kernel The kernel is the low-level software that manages hardware, multitasks programs, etc. 2. Linux Operating System Includes the kernel Also various utilities to get things done (program to copy files, etc) 3. Linux Distributions Software companies will sell extra software E.g. the desktop environment, games, etc. Ubuntu is one of many Linux distributions

3 November Licensing The GNU General Public License Linux is under This means that Linux can be: 1. Freely copied, changed, and distributed 2. No distribution restrictions can exist 3. The source code must be made available to the public

4 November How Can It Be Free? Linux developers make money by: 1. Custom applications for large companies 2. Tech support 3. Other jobs that don t involve Linux Linux (and the Open Source movement as a whole) is an example of how the highest quality results come from those who do work of their own free will

5 November Ubuntu Just one of many distributions or distros of Linux Oneiric Ocelot is version Released October 2011 Developed by Canonical Ltd. About 500 paid workers and thousands of volunteers Features: Unity Desktop Environment LibreOffice suite Ubuntu Software Center

6 November LibreOffice Fork of OpenOffice Development began January 2011 Oracle purchased Sun Microsystems in Jan 2010 Sun owned OpenOffice and developers didn t trust that Oracle would continue development Discontinued development on Sun s OpenSolaris operating system

7 November Package Management Maintains a database of software dependencies & version info Prevents software redundancies Automatically organizes software Ian Murdoch has called it the single biggest advancement Linux has brought to the industry Ubuntu uses the Ubuntu Software Center Can browse, download, and remove software

8 November Common Problems with Linux Cannot develop or pre-install proprietary drivers Doesn t always work fluidly with all hardware E.g. Mac touchpads Cannot run many proprietary software packages Larger learning curve

9 November Why Use The Command Line? A relatively simple string of text provides direct and unambiguous access to complicated tools

10 November POSIX Portable Operating System Interface for UniX As set of standards that Unix-y (including Linux) operating systems follow to provide portability Most basic command line tools are POSIX compliant Means that code written with Ubuntu can be easily run with Mac OSX or Debian or Gentoo or Damn Small Linux but not Windows

11 November OPEN THE TERMINAL Useful Commands cd ls cp cat echo mkdir pwd man less find date => change directory => list directory contents => copy files/directories => concatenate and print files => print text => make directories => prints working directory => open manual pages => read file with scrolling => search for files => print / modify date

12 November Navigation / => root directory ~ => home directory (also /home/<user>/ ).. => directory one level up. => current directory cd allows movement between directories Syntax: cd PATH_NAME PATH_NAME can be any of the symbols above, a directory name, or some combination for complex movement pwd will print the current directory in case you get lost

13 November Task #1: Navigate, Create, Destroy 1. Using the cd command, navigate to the Desktop Hints: The ls command will help you find the Desktop 2. Create a directory in the Desktop using mkdir NAME NAME can be anything you desire 3. Navigate into this new directory 4. Create a file and fill it with junk Use command echo JUNK > FILE_NAME 5. Read the contents with cat FILE_NAME 6. Read the contents with less FILE_NAME Exit less by hitting q 7. Remove the file with rm FILE_NAME

14 November Standard Files Standard Output is printed to the computer screen > will overwrite a file with a functions standard output >> will append the standard output to the end of a file Standard Input is by default what we type on the keyboard Use < to take input from a file Standard Error is an alternative type of output for errors Use 2> to overwrite a file with standard error

15 November Try $ cd ~ $ ls Desk > FILE_NAME $ cat FILE_NAME $ ls Desk 2> FILE_NAME $ cat FILE_NAME Note that the standard error is not only being written to the FILE_NAME but is being redirected from the terminal to FILE_NAME

16 November Input Arguments Try deleting the directory with the rm command. Tricky? Command line tools often use input arguments to extend their functionality Delete the directory with rm r DIRECTORY_NAME -r stands for recursive and will delete any file in the directory

17 November Save Time Hit the button at any point to recall the last command tab will fill in the remaining characters for file and directory names if there is only one possible option Use and tab often

18 November What s a Process? A process is a program in action Programs in executable form reside on disk, when run, they are moved into memory and become a process Linux assigns each process a Process Identification or PID

19 November Task #2: Process Handling $ gbrainy ctrl-c to kill $ gbrainy & $ ps $ baobab & $ ps $ kill <PID> $ history (do in new terminal) $ ps $ ps aux grep gbrainy $ top $ tty

20 November Nano Text Editor Nano is one of the simplest command line text editors To create a file, save it, and exit nano: $ nano FILE BWONGG wubwubwubwub <- enter text ctrl-o <- command to save ctrl-x <- command to exit nano

21 November Piping Symbol is the vertical line, Found at shift+backslash Takes standard output left of pipe and uses it as standard input to the function on the right of the pipe

22 November Piping Hot Example Create a file with a whole bunch of random words OR random text Make it so each SET of words or numbers have their own line While in that directory: $ sort FILE - if using numbers, sort g $ sort FILE grep ITEM $ sort FILE grep ITEM uniq $ sort FILE grep ITEM uniq -c

23 November APT Package Manager The Advanced Packaging Tool is what Ubuntu Software Center is built on apt-get install PACKAGE will install and organize software apt-cache list PACKAGE will search for PACKAGE in the local database apt-get update update the local package database

24 November FFMpeg FFMpeg is a multimedia transcoder Command line tools to convert sample rates, bit rates, file types, cut, copy, stream, and filter almost any audio, video, or image file We ll convert a lossless.flac file to an.mp3 for itunes $ sudo apt-get install ffmpeg $ cd DIRECTORY_OF_FLAC_FILE $ ffmpeg i FILE.flac NEW_FILE.mp3 $ man ffmpeg

25 LINUX USERS AND GROUPS MANAGEMENT

26 Introduction Ubuntu Linux uses groups to help you manage users, set permissions on those users, and even monitor how much time they are spending in front of the PC. Normally Linux computers have two user accounts your own user account, and the root account, which is the super user that can access everything on the PC, make system changes, and administer other users. Ubuntu works a little differently, though you can t login directly as root by default, and you use the sudo command to switch to root-level access when you need to make a change.

27 How Linux User Accounts Work Linux stores a list of all users in the /etc/groups file. You can run this command in the Terminal to to view and edit the groups and users in your system: sudo nano /etc/groups

28 How Linux User Accounts Work Username Password By default, all user home directories are created and maintained in the /home directory. However, the root user s home directory is /root

29 User Accounts storage Local This option stores user accounts in the /etc/passwd file. This has been the default configuration used by Linux systems for many years. /etc/passwd This file contains the user account information for your system. /etc/shadow This file contains passwords for your user accounts. /etc/group This file contains your system s groups

30 The Superuser By default, one account has elevated privileges to issue any command, access any file, and perform every function Superuser, a.k.a. root User and group number 0

31 The Superuser Must limit use of root Inexperienced users can cause serious harm Use of root for non-privileged tasks unnecessary and can be open to attack Security and privacy violations root can look at anyone s files Limit what root can do remotely Ensure a strong password

32 Superuser Privileges What usually works best is short periods of superuser privilege, only when necessary Obtain privileges, complete task, relinquish privileges Most common ways are su and sudo

33 su Short for substitute or switch user Syntax: su [options] [username] If username is omitted, root is assumed After issuing command, prompted for that user s password A new shell opened with the privileges of that user Once done issuing commands, must type exit

34 sudo Allows you to issue a single command as another user Syntax: sudo [options] [-u user] command Again, if no user specified, root assumed New shell opened with user s privileges Specified command executed Shell exited

35 sudoers Must configure a user to run commands as another user when using sudo Permissions stored in /etc/sudoers Use utility visudo to edit this file (run as root) Permissions granted to users or groups, to certain commands or all, and with or without password being required

36 Other permissions models Some Linux distributions such as Ubuntu obscure away the root account altogether By default the end user doesn t know the root password Can t login as root Can t su Must rely on sudo (and the graphical gksudo) to obtain privilege, along with Unlock functions in GUI

37 Using useradd Syntax: example: useradd options username useradd ken ken account is created using the default parameters contained in the following configuration files: /etc/default/useradd /etc/login.defs This file contains values that can be used for the GID and UID parameters when creating an account with useradd. It also contains defaults for creating passwords in /etc/shadow.

38 Using userdel Syntax: example: userdel username userdel ken It s important to note that, by default, userdel will not remove the user s home directory from the file system. If you do want to remove the home directory when you delete the user, you need to use the r option in the command line. For example, entering userdel r ken will remove the account and delete her home directory.

39 Managing groups Using groupadd Using groupmod Using groupdel groups are defined in the /etc/group file. Each record is composed of the following four fields: Group:Password:GID:Users Group Specifies the name of the group. In the example above, the name of the group is video. Password Specifies the group password.

40 Managing groups GID Specifies the group ID (GID) number of the group. Users Lists the members of the group. As with /etc/shadow, each line in /etc/gshadow represents a record for a single group. Each record is composed of the following fields: Group_Name:Password:Group_Admins:Group_Member s

41 Using groupadd Syntax: Options: groupadd options groupname g Specifies a GID for the new group. p Specifies a password for the group. r Specifies that the group being created is a system group

42 Using groupdel Syntax: groupdel group_name example: groupdel student

43 Managing ownership Anytime a user creates a new file or directory, his or her user account is assigned as that file or directory s owner. For example, suppose the ken user logs in to her Linux system and creates a file named linux_introduction.odt using OpenOffice.org in home directory. Because she created this file, ken is automatically assigned ownership of linux_introduction.odt.

44 How ownership works You can specify a different user and/or group as the owner of a given file or directory. To change the user who owns a file, you must be logged in as root. To change the group that owns a file, you must be logged in as root or as the user who currently owns the file. Using chown Using chgrp You can also view file ownership from the command line using the ls l command

45 Using chown The chown utility can be used to change the user or group that owns a file or directory. Syntax chown user.group file or directory. Example: If I wanted to change the file s owner to the ken1 user, I would enter chown ken1 /tmp/myfile.txt If I wanted to change this to the users group, of which users is a member, I would enter chown.users /tmp/myfile.txt Notice that I used a period (.) before the group name to tell chown that the entity specified is a group, not a user account. Ex: chown student.users /tmp/myfile.txt Note: You can use the R option with chown to change ownership on many files at once recursively.

46 Using chgrp In addition to chown, you can also use chgrp to change the group that owns a file or directory. Syntax: Example: chgrp group file (or directory) chgrp student /tmp/newfile.txt.