Lighttpd Traffic Shaping: Throttle Connections Per Single IP (Rate Limit)

Posted on in Categories Apache, CentOS, fedora linux, FreeBSD, Howto, Iptables, lighttpd, Linux, Networking, PF Firewall, RedHat/Fedora Linux, Security, Ubuntu Linux, UNIX last updated June 21, 2009

If you do not control or throttle end users, your server may run out of resources. Spammers, abuser and badly written bots can eat up all your bandwidth. A webserver must keep an eye on connections and limit connections per second. This is serving 101. The default is no limit. Lighttpd can limit the throughput for each single connection (per IP) or for all connections. You also need to a use firewall to limit connections per second. In this article I will cover firewall and lighttpd web server settings to throttle end users. The firewall settings can be applied to other web servers such as Apache / Nginx and IIS server behind PF / netfilter based firewall.

Download Fedora 11 CD / DVD ISO

Posted on in Categories Download of the day, fedora linux, Gnome, Linux, Linux desktop, Linux distribution, Linux Multimedia, package management, RedHat/Fedora Linux last updated June 10, 2009

Fedora Linux version 11 has been released and available for download ( jump to download link ). Fedora Linux is a community-based Linux distribution. Fedora is sponsored by Red Hat, Inc.

One of Fedora’s main objectives is not only to contain free and open source software, but also to be on the leading edge of such technologies. Fedora 11, codenamed “Leonidas”, was released on June 9, 2009. The features include ext4, a 20-second startup, and the latest GNOME, KDE and XFCE releases. Firefox 3.5 and Thunderbird 3’s latest pre-releases are available as well.

Linux Find Out If PCI Hardware Supported or Not In The Current Running Kernel

Posted on in Categories CentOS, Debian Linux, fedora linux, Gentoo Linux, GNU/Open source, Hardware, Howto, Linux, RedHat/Fedora Linux, Sys admin, Tips last updated June 3, 2009

From my mailbag:

How do I find out if a given PCI hardware is supported of by the current CentOS / Debian / RHEL / Fedora Linux kernel?

You can easily find out find out if a given piece of PCI hardware such as RAID, network, sound, graphics card is supported or not by the current Linux kernel using the following utilities under any Linux distributions.

Linux x86_64: Detecting Hardware Errors

Posted on in Categories CentOS, Debian Linux, fedora linux, Gentoo Linux, Hardware, Howto, kernel, Linux, Linux distribution, Networking, package management, RedHat/Fedora Linux, Shell scripting, Sys admin, Tips, Troubleshooting, Ubuntu Linux last updated June 2, 2009

The Blue Screen of Death (BSoD) is used for the error screen displayed by Microsoft Windows, after encountering a critical system. Linux / UNIX like operating system may get a kernel panic. It is just like BSoD. The BSoD and a kernel panic generated using a Machine Check Exception (MCE). MCE is nothing but feature of AMD / Intel 64 bit systems which is used to detect an unrecoverable hardware problem.

Program such mcelog decodes machine check events (hardware errors) on x86-64 machines running a 64-bit Linux kernel. It should be run regularly as a cron job on any x86-64 Linux system. This is useful for predicting server hardware failure before actual server crash.

Linux Kernel Security (SELinux vs AppArmor vs Grsecurity)

Posted on in Categories CentOS, Debian Linux, fedora linux, Gentoo Linux, GNU/Open source, Linux, Linux distribution, Networking, RedHat/Fedora Linux, Security, Slackware, Suse Linux, Ubuntu Linux last updated May 27, 2009

Linux kernel is the central component of Linux operating systems. It is responsible for managing the system’s resources, the communication between hardware and software and security. Kernel play a critical role in supporting security at higher levels. Unfortunately, stock kernel is not secured out of box. There are some important Linux kernel patches to secure your box. They differ significantly in how they are administered and how they integrate into the system. They also allow for easy control of access between processes and objects, processes and other processes, and objects and other objects. The following pros and cons list is based upon my personal experience.

Lighttpd mod_rrdtool: Monitor The Load, Requests Per Seconds and Traffic

Posted on in Categories CentOS, Debian Linux, fedora linux, Hardware, Howto, lighttpd, Linux, Monitoring, RedHat/Fedora Linux, Ubuntu Linux last updated May 23, 2009

The round-robin database tool aims to handle time-series data like network bandwidth, temperatures, CPU load etc. The data gets stored in round-robin database so that system storage footprint remains constant over time. Lighttpd comes with mod_rrdtool to monitor the server load and other details. This is useful for debugging and tuning lighttpd / fastcgi server performance.

How To Use Gmail Account To Relay Email From a Shell Prompt

Posted on in Categories Backup, Debian Linux, fedora linux, Howto, Linux, Linux desktop, RedHat/Fedora Linux, Tip of the day last updated April 5, 2009

Usually, you do not need to setup an email server under Linux desktop operating system. Most GUI email clients (such as Thunderbird) supports Gmail POP3 and IMAP configurations. But, how do you send mail via the standard or /usr/bin/mail user agents or a shell script? Programs such as sendmail / postfix / exim can be configured as a gmail smarthost but they are largely overkill for this use.

Security Through Obscurity: MAC Address Filtering ( Layer 2 Filtering )

Posted on in Categories data center, fedora linux, FreeBSD, Gentoo Linux, GNU/Open source, Hardware, Iptables, Linux, Networking, RedHat/Fedora Linux, Security, Ubuntu Linux, UNIX, Windows, windows vista, Wireless networking last updated February 17, 2009

MAC Filtering (layer 2 address filtering) refers to a security access control methodology whereby the 48-bit address assigned to each network card is used to determine access to the network. Iptables, pf, and IPFW can block a certain MAC address on a network, just like an IP. One can deny or allow from MAC address like 00:1e:2a:47:42:8d using open source firewalls. MAC address filtering is often used to secure LAN or wireless network / devices. Is this technique effective?

How To Tail (View) Multiple Files on UNIX / Linux Console

Posted on in Categories data center, Debian Linux, Download of the day, fedora linux, File system, FreeBSD, Gentoo Linux, GNU/Open source, Howto, Linux, Linux Log Management, Monitoring, package management, RedHat/Fedora Linux, Suse Linux, Sys admin, Tip of the day, UNIX last updated February 9, 2009

The tail command is one of the best tool to view log files in a real time using tail -f /path/to/log.file syntax on a Unix-like systems. The program MultiTail lets you view one or multiple files like the original tail program. The difference is that it creates multiple windows on your console (with ncurses). This is one of those dream come true program for UNIX sys admin job. You can browse through several log files at once and do various operations like search for errors and more.

Vsftpd Set Download Only Anonymous Internet Server

Posted on in Categories CentOS, fedora linux, Howto, Iptables, Linux, Networking, PF Firewall, RedHat/Fedora Linux, Security last updated January 21, 2009

This example shows how you might set up a large internet facing FTP site for distributing file or software updates. The emphasis will be on security and performance. VSFTPD will make sure only world-readable files and directories are served to the world via anonymous / ftp account. You force to originates FTP port connections from a secure port – so users on the FTP server cannot try and fake file content. You will hide the FTP server user IDs and just display ftp in directory listings. This is also a performance boost. Set a 40000-60000 port range for passive connections. This will help firewall setup.