In our previous IPTables firewall series article, we reviewed how to add firewall rule using “iptables -A”.

We also explained how to allow incoming SSH connection. On a high-level, it involves following 3 steps.

1. Delete all existing rules: “iptables -F”
2. Allow only incoming SSH: “iptables -A INPUT -i eth0 -p tcp –dport 22 -j ACCEPT”
3. Drop all other incoming packets: “iptables -A INPUT -j DROP”

The above works. But it is not complete. One problem with the above steps is that it doesn’t restrict the outgoing packets.
[continue reading…]

This is the 1st article in our new series on Linux performance monitoring and tuning.

Linux system administrators should be proficient in Linux performance monitoring and tuning. This article gives a high level overview on how we should approach performance monitoring and tuning in Linux, and the various subsystems (and performance metrics) that needs to be monitored.

[continue reading…]

This article gives step by step instructions on how to install Apache 2 with mod_ssl.

I prefer to install Apache from source, as it gives me more flexibility on exactly what modules I want to enable or disable, and I can also upgrade or apply patch immediately after it is released by the Apache foundation.
[continue reading…]

I would like to share this wonderful event in my life with all TGS readers.

We are blessed with a beautiful baby girl. Both mom and baby are doing well.

Holding this cute tiny package in my hands puts my life in perspective, and instantly gives me more meaning and purpose to my life. Words cannot express my happiness.

This article explains how to add iptables firewall rules using the “iptables -A” (append) command.

“-A” is for append. If it makes it easier for you to remember “-A” as add-rule (instead of append-rule), it is OK. But, keep in mind that “-A” adds the rule at the end of the chain.

Again, it is very important to remember that -A adds the rule at the end.
[continue reading…]

Question: How do I send signal to another process? Can you explain me all available options to send signals to a process in UNIX / Linux environment?

Answer: You can send various signals to processes using one of the methods explains in this article.
[continue reading…]

Press the power button on your system, and after few moments you see the Linux login prompt.

Have you ever wondered what happens behind the scenes from the time you press the power button until the Linux login prompt appears?

The following are the 6 high level stages of a typical Linux boot process.
[continue reading…]