1. 1 Begin to use Linux

2. 2 Background  Linux is an operating system similar to UNIX. It runs on many different computers and was first released in 1991.  The source code is opened, that is, available at no cost to anyone who wants to modify it.  There are of different versions of Linux in the market.  Want to learn more? Go to http://www.vbird.org

3. 3 Packages inside Linux  Apache, the most popular web server in the world.  vsftp, very secure file transfer protocol server.  Samba, let Linux become a Windows File Server.  SendMail, SMTP server  DHCP Server  Bind, DNS Server  MySQL, PostgresSQL, Database Server  iptables – A powerful firewall

4. 4 Try Linux with Putty  Putty is a Remote Shell which can let users run his own linux shell in a remote site  Open Putty in your Windows.  Under Host Name type: ictlab.tyict.vtc.edu.hk  Protocol MUST use SSH.  Click ‘Open’ to open a ssh terminal.  Username: your student id  Password: your HKID without bracket and MUST USE UPPER CASE, e.g G123456A

5. 5 Directories  Linux use ‘/’ as directories parser (Windows use ‘\’), e.g. /home/alan.  Files name and Directories name in Linux is case sensitive.  No Drives (A:, C: or D: ) name in Linux, you need to ‘mount’ a floppy or CD-ROM drives to a directories  All directories are started from ‘root directory /’  Each user has his/her ‘home directory’. For user ‘alan’, by default, his home directory is ‘/home/alan’.  Home directory for Super User ‘root’ is ‘/root’

6. 6 Commands to access Directories  All commands in Linux is case sensitive  cd /etc Change directory to /etc  cd ~ Change to your home directory  cd.. Move to the parent directory of the current directory.  cd - Move back to the previous directory you were in.

7. 7 Commands to access Directories (2)  ls -al List all files or directories name in long format under current directory  pwd Display current directory's absolute path.  mkdir work Create the directory ‘work’ in the current directory.  mkdir -p work/reports/2001/oct Create the directory work/reports/2001/oct, creating parent (-p) directories (work, work/reports, work/reports/2001) as required without danger of overwriting existing directories.

8. 8 Commands to access Files  cp a.txt backup/a_bk.txt Copy the file a.txt across to the directory backup and rename it a_bk.txt.  cp -r a b Copy the directory a into the directory b. The -r means recursive (i.e. the files and subdirectories contained in the directory, plus the files and subdirectories contained in the subdirectories, and so on).  mv a.txt work/reports Move the file a.txt across to the directory work/reports.  mv a.txt b.txt When you move a file to its current location, you rename it. In this case the file a.txt is renamed b.txt.

9. 9 Commands to access Files (2)  rm a.txt Remove the file a.txt.  rm -r work/reports To remove a directory (even an empty one) you need to add -r. Here the directory work/reports is removed.  touch report.txt Create an empty file (in this case report.txt), or if it already exists, update its access and modification time.  less dirs.txt View the dirs.txt file in the less program, allowing you to view large files, line by line. (Press q to quit.)

10. 10 Linux Installation  Press Enter for the first screen.  In each of the following steps, press ‘OK’ to proceed to the next step. (You can press ‘Tab’ to move your cursor to ‘OK’)  Select ‘English’ for language.  Select ‘US’ for keyboard.  Select ‘HTTP’ for media.  Select ‘DHCP’ for ip address.

11. 11 Linux Installation (2)  In Server name field, enter ictlab.tyict.vtc.edu.hk  In Directory field, enter /ftp/fedora/linux/core/4/i386/os  A graphical screen will comes up.  For Language Selection, choose ‘Chinese (Traditional)  For Install Type, choose ‘Custom’

12. 12 Linux Installation (3)  For Disk Partitioning Setup, choose ‘Manually partition with Disk Druid’  WARNING: YOU CANNOT TOUCH /hdc IN YOUR DISK PARTITION!  Create 3 partitions in Druid: /, file size 10000 /home, file size 10000 Swap, file size 1000  Do not use /hdc! Do not use LVM!  For the password, type ‘cmuser’.

13. 13 Linux Installation (4)  For Firewall Configuration, choose: Enable Firewall Check Remote Login, Web Server and File Transfer  WARNING: Disable SELinux!  For Package Group Selection, choose: Web Server Windows File Server FTP Server DNS Server Network Server

14. 14 Install Package with RPM  Go to http://ictlab.tyict.vtc.edu.hk/~alanpo and then download the Java Run Time (jre) RPM package to your home directory.  Open a terminal in your desktop  Type following command to install (jre): rpm -Uvh jre*.rpm Upgrades jre or installs the package if no previous version was found. U for upgrade, v for verbose (so you know what's going on), and h for hash (to show a progress bar).

15. 15 More about RPM  rpm -q jre Query RPM database, to display version of X- Chat installed. Useful for discovering if you have something installed.  rpm -qa | sort | less To display all (-a) RPMs installed, in alphabetic order, and in the less program.  rpm -e jre Uninstall (erase) the package webmin.

16. 16 Users Management in Linux

17. 17 root  All Linux distributions setup a special account called ‘root’ during installation.  The ‘root’ account gives you access to everything.  If your shell prompt ends with a hash/number- sign (#) you're logged-in as root. Normal user is a dollar-sign ($)

18. 18 Create a new user  Only ‘root’ can create and remove user accounts.  useradd alan Add a new user alan His home directory will be /home/alan  passwd alan Give this new account a password  finger alan List the user information of alan

19. 19 Remove a user  userdel alan Remove user alan  userdel -r alan Remove user alan and ALL THE FILES in his home directory

20. 20 su - substitute user  The su command allows you to temporarily become another user, until you press Ctrl+D to logout.  su Become root but you need to submit root’s password  su - alan Become alan.

21. 21 Group Management (2)  Arrange a GROUP of users can easily to apply some common policies to them.  Every user belongs to at least one group, their login group - given the same name as their user account.  groupadd students This will create the students group.  usermod -G students john Add user john to the group students.

22. 22 Group Management (3)  less /etc/group Show all groups and their members.  groupmod –n students tn_students Rename a group  groupdel tn_students Remove the group tn_students  groups Display groups you belong to.  groups john Display groups john belongs to.

23. 23 Access Rights  Three kinds of Access Rights: r – read, w – write, x – execute  Three kinds of people to access files: owner, group, others  To display the owner and group a file belongs to, enter ‘ls -l’ : -rw-rw-r-- 1 john tyict 1076 Nov 20 16:50 report.txt  First column (-rw-rw-r--) is Access Right  Third column (john) is owner  Fourth column (tyict) is group

24. 24 Access Right (2)  Here is the break of -rw-rw-r--:  Type: - for normal files, d for directories and l for Symbolic link  For owner rw-, he/she can read, write but cannot execute the file  For group rw-, same as owner  For others r--, he/she can read but cannot write or execute the file TypeOwnerGroupOthers -rw- r--

25. 25 Change Access Right  chown john report.txt Change owner of file report.txt, to john.  chown -R john. Change owner of all files and subdirectories (i.e. -R for recursively) in the current (.) directory, to john.  chgrp tn_stundents report.txt Change group of file report.txt, to tn_stundents.  chgrp -R tn_stundents. Change group of all files and subdirectories (i.e. -R for recursively) in the current (.) directory, to john.

26. 26 Change Access Right (2)  chmod a+rw report.txt Give all users read and write permission.  chmod go-wx report.txt Remove write and execute permission (-wx) from report.txt for group and others (go). For uuser (owner) ggroup oothers aall

27. 27 Change Access Right (3)  Permissions can also be set in octal (base 8), where read permission is a four, write is two, and execute is one. These you add up separately for user, group and other for between 000 (---------) and 777 (rwxrwxrwx), like so: