How to Restrict Access to specific Web sites with Squid Proxy

You can limit users’ ability to browse the Internet with access control lists (ACLs). Each ACL line defines a particular type of activity, such as an access time or source network, they are then linked to an http_access statement that tells Squid whether or not to deny or allow traffic that matches the ACL. Squid(…)

How to Restrict Web Access By Time in Squid

Users configure their web browsers to use the Squid proxy server instead of going to the web directly. The Squid server then checks its web cache for the web information requested by the user. It will return any matching information that finds in its cache, and if not, it will go to the web to(…)

How SSL Works

The SSL protocol includes two sub-protocols: the SSL record protocol and the SSL handshake protocol. The SSL record protocol defines the format used to transmit data. The SSL handshake protocol involves using the SSL record protocol to exchange a series of messages between an SSL-enabled server and an SSL-enabled client when they first establish an(…)

How to Display existing IPv6 addresses – Linux

First you should check, whether and which IPv6 addresses are already configured (perhaps auto-magically during stateless auto-configuration). Using “ip” Usage:   # /sbin/ip -6 addr show dev <interface>   Example for a static configured host:   # /sbin/ip -6 addr show dev eth0 2: eth0: <BROADCAST,MULTICAST,UP&gt; mtu 1500 qdisc pfifo_ fast qlen 100 inet6 fe80::210:a4ff:fee3:9566/10(…)

MySQL Database Replication Tips

1. MySQL Master-Master Replication Fails With ERROR 1200 (HY000) on Master 2. Password problem are solved by carefully checking your grant statements 3. When you have more than two master servers, you must use log-slave-updates option to ensure that changes are propagated in a chain. Beware of infinite looping of updates. Infinite loop is prevented(…)

How to see Memory Fragmentation in Linux Systems

When a Linux system has been running for a while memory fragmentation can increase which depends heavily on the nature of the applications that are running on it. The more processes allocate and free memory, the quicker memory becomes fragmented. And the kernel may not always be able to defragment enough memory for a requested(…)

How to Close Network Ports and Disabling Xinetd Services

The xinetd daemon is a replacement for inetd, the internet services daemon. It monitors the ports for all network services configured in /etc/xinetd.d, and starts the services in response to incoming connections. To check if xinetd is enabled and running, execute: # chkconfig –list xinetd xinetd 0:off 1:off 2:off 3:on 4:on 5:on 6:off # /etc/init.d/xinetd(…)

How to check the services which are started at bootup – Linux

On Red Hat systems you can list all services which are started at bootup using the following command: chkconfig –list |grep on You will notice that there are quite a lot of services enabled on your system. But many runlevel services (Stand-Alone Services) are not network related services like kudzu which is responsible for detecting(…)

How to Configure a DHCP Server – FreeBSD system

Unlike the built-in dhclient, your FreeBSD system does not come with DHCP server software. This is because you only need to configure a DHCP server if you want to lease out IP configuration for your own network. However, there are two ports that allow you to create your own DHCP server. The first is known(…)

How to remove a Trojan, Virus, Worm, or other Malware.

If you use a computer, read the newspaper, or watch the news, you will know about computer viruses or other malware. These are those malicious programs that once they infect your machine will start causing havoc on your computer. What many people do not know is that there are many different types of infections that(…)

How to setup NIC team on a HP ProLiant DL 380 for fault tolerance and Load Balance

NIC teaming is the process of grouping together several physical NICs into one single logical NIC, which can be used for network fault tolerance and transmit load balance. The process of grouping NICs is called teaming. Teaming has two purposes: • Fault Tolerance: By teaming more than one physical NIC to a logical NIC, high(…)

How to Install and Configure pfSense – A free, open source firewall and router

pfSense is a free, open source customized distribution of FreeBSD tailored for use as a firewall and router. In addition to being a powerful, flexible firewalling and routing platform, it includes a long list of related features and a package system allowing further expandability without adding bloat and potential security vulnerabilities to the base distribution.(…)