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 February 9, 2010

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.

Visual Representations Of Linux File Systems

Posted on in Categories File system, Howto, kernel, Linux last updated June 18, 2009

This is an interesting visualization techniques for software analysis. From the article:

Despite being a very important part of any operating system, file systems tend to get little attention. Linux has three editions for Linux Device Drivers, another three for Understanding the Linux Kernel and two for Linux Kernel Development. The first is a detail analysis of one particular Linux Kernel tree and the second is a shorter one done over a large number of file systems from Linux Kernel 2.6.0 to 2.6.29. After that there is a small section that shows some aspects of the BSD family. After conclusions there is an appendix consisting of three things: the first one explains how the file systems for Linux were compiled, the second one shows timelines for the releases of Linux Kernel, FreeBSD, NetBSD and OpenBSD; the last is a detailed map of the external symbols of the kernel modules analyzed in the second section.

A Visual Expedition Inside the Linux File Systems

Increase Your VMware Virtual Hard Disk Size ( vmdk file )

Posted on in Categories Backup, Hardware, Howto, Linux desktop, Linux Virtualization, Storage, Sys admin, Tips, Ubuntu Linux, vmware, windows vista last updated June 18, 2009

I’ve Windows Vista installed as a guest under Ubuntu Linux using VMWARE Workstation 6.0. This is done for testing purpose and browsing a few site that only works with Internet Explorer. Since I only use it for testing I made 16GB for Vista and 5GB for CentOS and 5GB in size for FreeBSD guest operating systems. However, after some time I realized I’m running out of disk space under both CentOS and Vista. Adding a second hard drive under CentOS solved my problem as LVM was already in use. Unfortunately, I needed to double 32GB space without creating a new D: drive under Windows Vista. Here is a simple procedure to increase your Virtual machine’s disk capacity by resizing vmware vmdk file.

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 18, 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.

OpenOffice.org Quick Introduction For New User

Posted on in Categories GNU/Open source, Howto, Linux desktop, OpenOffice.Org, Troubleshooting, Ubuntu Linux, UNIX, Windows, windows vista last updated June 18, 2009

OpenOffice.org (OOo) is a freely available, full-featured office suite. OOo is both a software product and a community of volunteers that produces and supports the software. However, new users may get lost while finding help, support and productivity enhancing extensions. This blog post covers OOo new user orientation to to discover support, tutorials, community insights, templates, clip art, extensions, and blogs for OOo.

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 18, 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.

ss: Display Linux TCP / UDP Network and Socket Information

Posted on in Categories Debian Linux, Howto, Linux, Monitoring, Networking, RedHat/Fedora Linux, Sys admin, Tips, Troubleshooting, Ubuntu Linux last updated September 1, 2014

The ss command is used to show socket statistics. It can display stats for PACKET sockets, TCP sockets, UDP sockets, DCCP sockets, RAW sockets, Unix domain sockets, and more. It allows showing information similar to netstat command. It can display more TCP and state information than other tools. It is a new, incredibly useful and faster (as compare to netstat) tool for tracking TCP connections and sockets. SS can provide information about:

  • All TCP sockets.
  • All UDP sockets.
  • All established ssh / ftp / http / https connections.
  • All local processes connected to X server.
  • Filtering by state (such as connected, synchronized, SYN-RECV, SYN-SENT,TIME-WAIT), addresses and ports.
  • All the tcp sockets in state FIN-WAIT-1 and much more.