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Building a Linux Network Appliance, Part 3 - page 2

Building the Firewall

  • July 6, 2006
  • By Carla Schroder

Our first job is to install Webmin. Webmin is an excellent multiple-purpose graphical interface for managing Linux hosts, and will be our primary system administration interface in this series. Webmin is modular, so you install only the pieces that you need.

If you're not logged in to your firewall box, log in now as the root user, then install Webmin:

root@firewall1:~# apt-get install webmin webmin-core webmin-firewall

apt-get will wait for a confirmation before starting the installation. If you can't see all the output, you can scroll up and down by holding down the Shift key while pressing the Page Up/Page Down keys.

The next step is to enable remote Webmin administration. By default, access is limited to localhost, so you need to edit /etc/webmin/miniserv.conf:

root@firewall1:~# nano /etc/webmin/miniserv.conf

Add this line, using the IP of the computer you'll be logging in from:

allow=192.168.1.15

Or, you can allow access from your entire subnet, which for this example is 192.168.1.0. Save your changes and restart Webmin:

root@firewall1:~# /etc/init.d/webmin restart

Next, change the root password. Webmin has its own password file, so you can protect your system login. Use this command:

root@firewall1:~# /usr/share/webmin/changepass.pl /etc/webmin root [newpassword]

Now go to a neighboring PC, fire up your Web browser of choice, and go to https://[hostname or IP]:10000/. You will get a warning about the SSL certificate that was created when Webmin was installed. Go ahead and accept the certificate, then log in as root with your new Webmin password, and you will see a screen like Figure 1.

fig1-webmin1
Figure 1.

Click on the tabs and take a look around. Notice how the root user has complete powers to do anything. If you're going to delegate some administration jobs you may create a second user on the Webmin -> Webmin Users tab, and give this user specific, limited powers.

The last step before creating our firewall is to configure networking. The Webmin networking module isn't all that helpful, so we'll configure it manually, plus we'll use ifrename to make sure the configurations stick to the correct interface. We'll cover that in our next installment.

Resources

This article first appeared on Practically Networked, a JupiterWeb site.

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