Firewall Configuration (GUI)

This section describes how to use the Firewall Configuration tool to configure the firewall.

1. Click System, select Administration and click Firewall. This will launch the Firewall Configuration window.

2. Click Close in the Firewall Configuration Startup window.

3. Type in the root password and click Authenticate.

If the Firewall Configuration Startup window does not disappear after clicking Close, click the window behind it to bring the Authenticate window into the foreground.

4. In the service list, check Mail (SMTP) and WWW (HTTP).

5. Click Other Ports and click Add.

6. Select 110 tcp pop3 and click Ok. Do the same for 143 tcp imap.

7. Finally, click Apply to save your changes.

Firewall Configuration (TUI)

This section describes how to use the Firewall Configuration text user interface (TUI) tool to configure the firewall.

1. Launch the Firewall Configuration tool using the command below.

system-config-firewall-tui

2. In Firewall Configuration screen, press the Customize button.

3. In the service list, check Mail (SMTP) and WWW (HTTP). Press Forward when you are done.

4. Press Add to add a custom port.

5. Type in 110 to the field Port and tcp to the field Protocol. Press OK when you are done. Do the same for 143:tcp.

6. After adding the two ports press Close.

7. Finally, press OK and press Yes to confirm overriding of firewall configuration.

You can see the list of service and port numbers using the command below.

getent services

Manage Services (RHEL 6)

This section describes how to manage the services using the Service Configuration tool.

1. Click System, select Administration, and click Services. This will launch the Service Configuration window.

2. In the Service Configuration window, select the service you wish to run when the system starts and click Enable.

3. To immediately run the service, click Start.

Make sure xinetd is running if you enable any on demand services.

Manage Services (RHEL 5)

This section describes how to manage the services using the Service Configuration tool.

1. Click System, select Administration, select Server Settings and click Services. This will launch the Service Configuration window.

2. In the Service Configuration window, check the service you wish to start on the next system startup, in this case the service postfix. To start the service immediately, press Start.

 

Unchecked services will not be started on the next system startup. To immediately stop a service, select the service and press Stop.

 

To restart a service, select the service and press Restart.

3. Press Save to save your changes.

4. You can also do the same for On-Demand Services.

Make sure xinetd is running if you enable any On-Demand Services. You can find xinetd in the Background Services tab.

Manage Services (Console)

Listed below are the console commands to manage the services. You need to have root level access to use the commands below.

/sbin/chkconfig ––list

/sbin/chkconfig [name] on

/usr/sbin/update-rc.d [name] defaults

/sbin/chkconfig [name] off

/usr/sbin/update-rc.d -f [name]
 remove

/sbin/service [name] start

/usr/sbin/service [name] start

/sbin/service [name] stop

/usr/sbin/service [name] stop

/sbin/service [name] restart

/usr/sbin/service [name] restart

/sbin/service [name] status

/usr/sbin/service [name] status

File Management (GUI)

Managing files in GUI mode is a simple as launching the File Browser.

1. Click Applications, select System Tools then click File Browser. This will launch the File Browser window.

2. From the File Browser tool you can now perform your desired file operation.

File Management (Console)

Below are the console commands to manage files. This is just an overview of the commands available, to get more information, type in man command to get the manual for the specified command.

Common Operations

• cp -a source dest
  copy the specified file or directory
• rm -rf name
  delete the specified file or directory and all of its contents
• mv old new
  move a file or directory to a new location. Also used to rename a file or directory
• ln -s source linkname
  create a symbolic link to the specified file or directory

Directory Operations

• cd
  change to the home directory
• cd path
  change to the specified directory
• pwd
  print working directory
• ls
  list directory
• mkdir name
  create the specified directory
• rmdir name
  delete the specified directory. Directory should be empty

File Operations

• chown owner file
  change the file owner to the specified user
• chmod permissions files
  change the file permissions
• cat file
  shows the file content
• more file
  shows the file content a few screens at a time
• less file
  shows the file content similar to how vi displays a file
• vi file
  edit the specified file. Learn how to use the vi editor
• head file
  shows the first few lines of a file
• tail file
  shows the last few lines of a file
• sort file
  shows the file content in order by lines
• uniq file
  shows the file content, discarding all but one of successive identifical lines
• grep pattern file
  searches for the pattern inside the specified file
• file filename
  determine file type
• diff file1 file1
  compares two files

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Linux Command Line and Shell Scripting Bible

It is painful to work with Linux if you are not familiar with its arcane commands. Googling the right command for every problem encountered wastes a lot of valuable time.

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Configure Network Device (GUI)

This section describes how to configure the network device using GUI tools.

1. Click System, select Administration then click Network. This will launch the Network Configuration window.

2. Select the network device you want to modify and click Edit.

3. In the Ethernet Device window, apply your changes and click OK.

4. Click the DNS tab and apply your DNS settings.

5. To save your changes, click the File and click Save.

6. To effect your changes, click the Devices tab. Next, select the device and click Deactivate then click Activate to reactivate the device.

7. Update your /etc/hosts file.

Although the Network Configuration tool has a feature to update the /etc/hosts file, it is more reliable to edit it directly instead.

Configure Network Device (TUI)

This section describes how to configure the network device using text user interface (TUI) tools.

1. Launch the Network Configuration TUI tool using the command below. Then apply the necessary changes to your network device.

system-config-network-tui

2. To effect your changes, restart the network service using the command below.

service network restart

3. Update your /etc/hosts file.

Configure Hosts

1. Click Applications, select System Tools then click File Browser. This will launch the File Browser window.

2. In the Location field, type in /etc and press Enter. If you don’t see the Location field, click the notepad button to toggle to text-based location bar.

3. Locate and double click on the file hosts to open it for editing. Update the content similar to the lines below.

127.0.0.1       localhost.localdomain localhost
::1             localhost6.localdomain6 localhost6
192.168.0.4     mail.acme.local mail

Replace the last line with your own IP address, fully qualified domain name and host name.

Test the Host Name Lookup

1. Click Applications, select Accessories, and click Terminal. This will launch the Terminal window.

2. In the terminal window, type in the command below.

ping localhost

You should see localhost.localdomain and 127.0.0.1

3. Next, type in the command below.

ping mail

Replace mail with your own hostname. You should see your fully qualified domain name and ip address.

Configure NTP (GUI)

This section describes how to configure the NTP using the Date & Time GUI tool.

1. Click System, select Administration and click Date & Time.

2. In the Date/Time Properties window, click the Network Time Protocol tab.

3. Check Enable Network Time Protocol. Next click Show advanced options and check Synchronize system clock before starting service. Finally, click OK.

Configure NTP (Console)

Listed below are the commands to configure the NTP. You need to have root level access to use the commands below.

• /usr/sbin/ntpdate pool.ntp.org
  immediately synchronizes the system clock. Make sure the ntpd service is not running before using this command.
• /sbin/service ntpd start
  starts the ntpd service
• /sbin/service ntpd stop
  stops the ntpd service
• /etc/ntp.conf
  the above is not a command, it is the location of the ntpd configuration file

System Management

This section describes how to perform system management tasks.

How to manage directories and files

How to add, edit or remove a user account

How to add or remove packages or applications

How to start, stop or restart a background service
How to enable or disable an on demand service

How to configure a network device

How to configure the firewall

How to synchronize the system clock using NTP

System Utilities

This section describes utilities you can use to manage your system.

How to setup SSH to remotely administer a Linux server using a command line

How to use VNC to remotely administer a Linux server using a GUI

How to setup Webmin, a web based system administration tool

How to use rsync to synchronize files between two computers

How to use vi, a command line editor

Adding RPMforge to Yum

The rpmforge repo package can be downloaded from the site below.

1. Launch Firefox and go to http://dag.wieers.com/rpm/FAQ.php#B2. Click on the package appropriate for your version of Red Hat Enterprise Linux or CentOS.

2. Choose Open with Software Installer (default) and click Ok.

3. The Installing packages window will appear. Click Apply to proceed.

4. Finally click Ok.

Lowering the RPMforge priority

Lowering the priority of the RPMforge repository will ensure that the base packages provided by RHEL/CentOS will not be replaced by a newer version from RPMforge.

1. Install the Yum priorities package using the command below.

yum install yum-priorities

2. Edit the file /etc/yum.repos.d/rpmforge.repo and add the line below.

priority=10

3. Test your configuration using the command below. You should see a priority protections message in the output.

yum check-update