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. Delete all existing rules: “iptables -F” Allow only incoming SSH: “iptables -A INPUT -i eth0 -p tcp –dport 22 -j ACCEPT” [...]
Linux
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 [...]
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. [...]
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 [...]
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. 1. Send Signal to a Process Using Kill Use kill command [...]
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. 1. [...]
You would set the sticky bit primarily on directories in UNIX / Linux. If you set the sticky bit to a directory, other users cannot delete or rename the files (or subdirectories) within that directory. When the sticky bit is set on a directory, only the owner and the root user can delete / rename [...]
On Red Hat based Linux, iptables comes with certain default rules. It is good idea to clean them up, and start from scratch. This article is part of an ongoing iptables tutorial series. This is the 2nd article in that series. In our 1st part, we discussed about IPTables Tables, Chains, Rules Fundamentals. Before we [...]
My name is Ramesh Natarajan. I will be posting instruction guides, how-to, troubleshooting tips and tricks on Linux, database, hardware, security and web. My focus is to write articles that will either teach you or help you resolve a problem. Read more about