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Begin to use Linux

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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

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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

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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

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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’

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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.

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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.

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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.

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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.)

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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.

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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’

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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’.

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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

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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).

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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.

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Users Management in Linux

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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 ($)

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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

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Remove a user userdel alan

Remove user alan userdel -r alan

Remove user alan and ALL THE FILES in his home directory

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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.

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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.

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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.

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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

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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

Type Owner Group Others

- rw- rw- r--

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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.

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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

u user (owner)

g group

o others

a all

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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: