This article uses postfix as the mail transport agent (MTA), as opposed to sendmail, the default MTA for CentOS. Dovecot is used to allow users to access their email by either imap or pop protocols. We assume a domain name of example.com which should be changed by the reader and can be either a real [...]

This allows full access through our firewall to certain trusted sources (host PCs). Now we’ll look at how we can filter against protocols and ports to further refine what incoming packets we allow and what we block. Before we can begin, we need to know what protocol and port number a given service uses. For [...]

Successfully networking your Ubuntu system with Windows clients involves providing and integrating with services common to Windows environments. Such services assist the sharing of data and information about the computers and users involved in the network, and may be classified under three major categories of functionality: File and Printer Sharing Services. Using the Server Message [...]

If a user is authenticated at the proxy you cannot “log out” and re-authenticate. The user usually has to close and re-open the browser windows to be able to re-login at the proxy. A simple configuration will probably look like this:   acl my_auth proxy_auth REQUIRED http_access allow my_auth http_access deny all But there is [...]

A number of commands can provide information about your newly created database. Here are some examples: Login As The Database User: It is best to do all your database testing as the MySQL user you want the application to eventually use. This will make your testing mimic the actions of the application and results in [...]

On many occasions you will not only have to create a database, but also have to create a MySQL username and password with privileges to access the database. It is not a good idea to use the root account to do this because of its universal privileges. MySQL stores all its username and password data [...]

SafeSquid has an option in ‘Network Settings’, to add new interface for outgoing connection.This is useful in networks where you need to split the load between different ISPs. It can also be useful to switch different ISPs due to slow net connection or discontinuity.This can be accomplished by following way: You wish to – 1. [...]

Type the following command from the terminal prompt. If you are using a distro other than Ubuntu, make sure that your user account has sudo permissions, otherwise you might have to use su to switch to root before entering the command. sudo dhclient -r Output: Internet Systems Consortium DHCP Client V3.0.5 Copyright 2004-2006 Internet Systems [...]

This is an introductory guide for people learning to use a Linux system. It focuses on command-line usage. This is not because everyone will be doing everything at the command line. On the contrary, there are many useful GUI tools and programs in Linux, and some people will be content to stay with these. However, in contrast to GUI programs, which can be learned largely by “click and try”, the command-line requires some deliberate learning, and reading documentation. The benefit of this investment is that you will learn the tools and tricks of the command line which are in many cases faster, more powerful, and more flexible than any GUI program.

As a system administrator, part of your daily duties is to monitor systems for performance and to tune systems where necessary. While there are expensive software products and benchmarking tools that can hone a machine to optimum efficiency, there exist several basic tools within Linux® that permit the knowledgeable system administrator to gather information and [...]

Websense Express installs with Windows NT Directory as its default directory service. If your network uses Active Directory, you cannot assign policies to users until you reconfigure the directory service settings in Websense Manager. Filtering can occur with the wrong directory service selected, but user data is logged incorrectly. In addition, user-based policies cannot be [...]