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HowTo: HTTP Status: 206 Partial Content and Range Requests Using Curl

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The HTTP 2xx class of status codes indicates the action requested by the client was received, and processed successfully. HTTP/1.1 200 OK is the standard response for successful HTTP requests. When you type www.cyberciti.biz in the browser you will get this status code. The HTTP/1.1 206 status code allows the client to grab only part of the resource by sending a range header. This is useful for:

* Understanding http headers and protocol.
* Troubleshooting network problems.
* Troubleshooting large download problems.
* Troubleshooting CDN and origin HTTP server problems.
* Test resuming interrupted downloads using tools like lftp or wget or telnet.
* Test and split a large file size into multiple simultaneous streams i.e. download a large file in parts. read more...
mail this link | permapage | score:9758 | -nixcraft, November 21, 2012

Tutorial: Fedora 19 Samba server with tdbsam

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This tutorial explains the installation of a Samba fileserver on Fedora 19 and how to configure it to share files over the SMB protocol as well as how to add users. Samba is configured as a standalone server, not as a domain controller. In the resulting setup, every user has his own home directory accessible via the SMB protocol and all users have a shared directory with read-/write access. read more...
permapage | score:9746 | -falko, August 11, 2013

Linux Iptables Examples

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Linux comes with a host based firewall called Netfilter. It is a set of hooks inside the Linux kernel that allows kernel modules to register callback functions with the network stack. A registered callback function is then called back for every packet that traverses the respective hook within the network stack.

This Linux based firewall is controlled by the program called iptables to handles filtering for IPv4, and ip6tables handles filtering for IPv6. This tutorial list most common iptables solutions required by a new Linux user to secure his or her Linux operating system from intruders. read more...
mail this link | permapage | score:9745 | -nixcraft, December 14, 2011

Tutorial: Ubuntu Jeos 12.04 LTS Spam Filter Gateway Server

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This tutorial shows how to set up an Ubuntu Jeos based server as a spamfilter in gateway mode. In the end, you will have a SpamSnake Gateway which will relay clean emails to your MTA. You will also be able to view your incoming queue, train your SpamSnake and carry out a few more advanced operations via Baruwa. read more...
permapage | score:9744 | -falko, December 23, 2012

Installing FreeIPA with Replication

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Do you need a single point to add users within your organization for authenticating to multiple backends like your Linux servers? You've probably looked at OpenLDAP and found the same problem a lot of other users have: bad documentation and ridiculously hard to configure. Having done some installations of OpenLDAP in the past, the search was on to find a good alternative and more importantly, one that is far easier to do and has a good gui and CLI for adding users and groups. read more...
permapage | score:9739 | -falko, June 6, 2013

Using OpenVZ on Debian 7 (AMD64)

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In this HowTo I will describe how to prepare a Debian Wheezy server for OpenVZ. With OpenVZ you can create multiple Virtual Private Servers (VPS) on the same hardware, similar to Xen and the Linux Vserver project. OpenVZ is the open-source branch of Virtuozzo, a commercial virtualization solution used by many providers that offer virtual servers. The OpenVZ kernel patch is licensed under the GPL license, and the user-level tools are under the QPL license. read more...
permapage | score:9729 | -falko, June 7, 2013

Tutorial: Install Lighttpd, PHP5, MySQL on CentOS 6.4

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Lighttpd is a secure, fast, standards-compliant web server designed for speed-critical environments. This tutorial shows how you can install Lighttpd on a Centos 6.4 server with PHP5 support (through PHP-FPM) and MySQL support. PHP-FPM (FastCGI Process Manager) is an alternative PHP FastCGI implementation with some additional features useful for sites of any size, especially busier sites. I use PHP-FPM in this tutorial instead of Lighttpd's spawn-fcgi. read more...
permapage | score:9723 | -falko, April 17, 2013

QEMU-KVM 1.0 patching for USB Redirection on Ubuntu 12.04

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Qemu-kvm 1.0 has been built based on branch
qemu-kvm-1.0-usbredir as of 12/29/2011. It contains all required usb redirection patches on top of QEMU-KVM 1.0 release

$ git clone git://people.freedesktop.org/~jwrdegoede/qemu
$ cd qemu
$ git checkout -B qemu-kvm-1.0-usbredir origin/qemu-kvm-1.0-usbredir
$ cd ..
$ cp -R qemu qemu-kvm-1.0-usbredir1 read more...
permapage | score:9720 | -Boris Derzhavets, December 31, 2011

Apple DIY Repair

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I won't be buying any more Apple products. Here's why:

I'm generally capable of repairing my own equipment and can recognize when self-repair has been deliberately undermined. I recently had to replace a hard drive in an early generation white Intel iMac. Innocently, I believed the interior was accessible and serviceable in the manner of the externally identical white PowerPC iMacs.

No such luck. Not only do you have to remove the LCD to get to the hard drive, but you must also remove shielding around the LCD -- mostly by tearing it to bits. No doubt it is attached this way so that an authorized Apple technician will be able to confidently void your warranty if you've ever worked on the system yourself.

You'll also need a #10 torx magnetic screwdriver. And, no, #10 torx bits just won't do due to the narrow and deeply recessed screw holes. Also, since most torx screwdrivers aren't magnetic, you'll probably need to tape the screws to the screwdriver to reattach the LCD. Good thing there's a hardware store near you.

Oh, and don't forget to pick up some rubber cement to 'properly' reattach the hard drive temperature sensor while you're out looking for magnetic torx screwdrivers.

Considering the logical design of its predecessor and the tamper-evident shielding, I'm certain that this machine has been deliberately designed to prevent the owner from performing DIY upgrades and repairs.

While that is all quite annoying, at least working on the system is possible for someone with experience and determination.

Now, Apple has improved their anti-customer techniques with the 'Pentalobe' screw. It doesn't solve any problem but one: it'll keep customers from even being able to open the case.

If you're curious about Apple's evil new invention, you can read its rap sheet and view its mug shot here.
mail this link | permapage | score:9713 | -Ray, January 25, 2011

Alternative operating systems

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The ten best alternative OSes, none of which are from Microsof or Apple, nor are any based on Linux. Operating systems covered are:
  • GNU/HURD (RMS' never-quite-done free OS, predates Linux(!))
  • JNode (written in Java)
  • FreeVMS (DEC's famous VMS)
  • DexOS (tiny, console-like GUI)
  • Inferno (distributed, device-sharing)
  • KolibriOS (MenuetOS fork, tiny, written in Assembly)
  • OpenBSD (a BSD variant specializing in security, correctness)
  • AROS (Amiga Research Operating System )
  • ReactOS (Windows clone)
  • Haiku (BeOS clone)
From the article:
Big companies can grow reticent to change, slow to move and adopt new technologies. Features must be escalated through approval bodies, management and bean-counters. Hobbyist projects don't have those commercial pressures and can experiment freely.

It might seem audacious to claim that the next Windows is cooking in some part-time coder's house, but it's nothing new. Microsoft's OS empire started with the purchase of QDOS, which stood for 'Quick and Dirty Operating System'. Apple didn't create Mac OS X out of thin air, but took an open source kernel and some BSD code (grounded in academia) to get the foundations of its operating system working.
read more...
mail this link | permapage | score:9687 | -Ray, March 16, 2011

Tutorial: Build an OpenSUSE 12.2 x86_64 Server

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This is a detailed description about how to set up an OpenSUSE 12.2 64bit (x86_64) server that offers all services needed by ISPs and hosters: Apache web server (SSL-capable) with PHP, CGI and SSI support, Postfix mail server with SMTP-AUTH, TLS and virtual mail users, BIND DNS server, Pureftpd FTP server, MySQL server, Dovecot POP3/IMAP, Quota, Firewall, Mailman, etc. Since version 3.0.4, ISPConfig comes with full support for the nginx web server in addition to Apache; this tutorial covers the setup of a server that uses Apache, not nginx. read more...
mail this link | permapage | score:9683 | -falko, September 12, 2012

Linux find command examples: finding files

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This is a quick tutorial on how to use the find command to search for files from the commandline. The find command is a powerful commandline tool in linux that can search files based on various criterias like name, modification date, size, permission etc. read more...
permapage | score:9675 | -Silver Moon, August 13, 2013

Server Monitoring With munin And monit On Debian Wheezy

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In this article I will describe how you can monitor your Debian Wheezy server with munin and monit. munin produces nifty little graphics about nearly every aspect of your server without much configuration, whereas monit checks the availability of services like Apache, MySQL, Postfix and takes the appropriate action such as a restart if it finds a service is not behaving as expected. The combination of the two gives you full monitoring: graphics that lets you recognize current or upcoming problems, and a watchdog that ensures the availability of the monitored services. read more...
mail this link | permapage | score:9672 | -falko, June 27, 2013

Build a Mail Server on CentOS 6 with Postfix, Dovecot, PostgreSQL

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We're going to set up a free, full-featured mail server on CentOS 6.2, all mail service related components are free and open source, and you have control over your own data. The installation process is extremly easy and smooth. read more...
permapage | score:9649 | -falko, April 29, 2012

Tutorial: Replace Windows with Ubuntu 13.04

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This tutorial shows how you can set up an Ubuntu 13.04 desktop that is a full-fledged replacement for a Windows desktop, i.e. that has all the software that people need to do the things they do on their Windows desktops. The advantages are clear: you get a secure system without DRM restrictions that works even on old hardware, and the best thing is: all software comes free of charge. read more...
permapage | score:9643 | -falko, May 5, 2013

VPS: Xen vs. OpenVZ

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This is a short overview of the key differences between OpenVZ and Xen that you might consider when choosing a VPS. Note that this article is based on my opinions and that you must do your own research to determine which, if either, technology is best for you and your application.

First, some terminology. OpenVZ isn't fully virtualized and could be more properly referred to as a 'container', not a VPS. That shouldn't affect your choice. It's the technical differences that matter.

Cheap VPS offers are everywhere lately, it seems. However, upon closer inspection I saw that almost all of the low-priced offers were for OpenVZ. While both Xen and OpenVZ offer their advantages, I chose Xen. So, there's my first bias, right up front. :)

OpenVZ advantages:

  • Efficient (fast)
OpenVZ disadvantages:
  • Shared kernel (no custom kernel)
  • Shared memory with other users
  • Vendor can easily oversell, killing performance
Xen advantages:
  • Dedicated memory
  • fully virtualized (can run other kernels or even OS's)
  • vendor more limited in overselling
Xen disadvantages
  • Less efficient (more overhead due to a kernel-per-VPS)

You'll notice I left price out of the above comparison. In theory, there should be a small price advantage for OpenVZ. I don't know how big it should be but it pertains to two things: 1) Xen uses more memory due to each VPS having its own kernel, and 2) Xen uses more CPU, also due to the additional software layer required to virtualize the kernel.

In practice, however, the price gap appears larger than the above technical differences suggest it should be. I think the remainder of OpenVZ's price advantage is based on 1) the ability for a vendor to easily oversell OpenVZ, and 2) The price competition that results from some vendors overselling OpenVZ.

OpenVZ doesn't encapsulate its containers into a fixed amount of memory, so it runs processes in the host environment to monitor memory usage and kill processes as a container allocates more than its assigned amount.

As a result of this difference, loading down an OpenVZ container is problematic. To partially offset this disadvantage, most OpenVZ vendors offer 'burst' memory in addition to 'dedicated' memory. That is, the monitor process is set to allow the container to use more than its allocated memory -- for a short period of time. This messy situation results in a potentially unreliable environment as some of your processes may be arbitrarily killed -- at the busiest times.

Xen, on the other hand, allows the use of a swap space and excess memory allocation results in (hopefully) idle segments being rolled out to the swap area. While this is good for the memory-hungry VPS user, it can consume significant I/O capacity when memory is overallocated to the point of busy segments getting swapped out. This is bad for everyone sharing the underlying hardware.

I see Xen as clearly the superior technology. A Xen VPS feels and behaves more like a dedicated server. However, I still would have purchased OpenVZ at some price difference. After a bit of research, however, I located Xen VPS's at practically the same price as the cheapest OpenVZ containers. That made my decision easy.

With that said, keep in mind that a bad hosting vendor can ruin either technology through various means. Both technologies share the disk drives and I/O paths as well as the processor cores. Hardware can be poorly configured and managed in any case. A reputable vendor is probably the single most important consideration in choosing a virtual server.

Lastly, carefully check the 'allowed use' policy. Make sure your application is allowed on the server you intend to purchase. Note that due to their different characteristics, the allowed use policy may differ between OpenVZ and Xen for the same host. Also, it's good to understand the memory usage characteristics of your applications. If you know how much memory/swap they require on a physical system, it'll probably work with that same amount of memory/swap on Xen.

[I'll post a review shortly of my current VPS vendor and I will then add a link to that article here.]

mail this link | permapage | score:9625 | -Ray, June 13, 2011

System monitoring: Icinga, Nagios, and Opsview

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Three open-source system monitoring software packages, two of which are derived from Nagios...
If in your work you are responsible for just one server, you will surely wonder: What is the best way to get the situation under control?

In the world there are good open source software that allow you to monitor the status of servers, services and programs.

In this article we’ll see an overview some of the softwares in this category, and in particular some related to Nagios...
read more...
mail this link | permapage | score:9615 | -Ray, March 24, 2011

Lynis: Security and system auditing tool

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Lynis is an auditing tool for Unix (specialists). It scans the system and available software, to detect security issues. Beside security related information it will also scan for general system information, installed packages and configuration mistakes.This software aims in assisting automated auditing, software patch management, vulnerability and malware scanning of Unix based systems. It can be run without prior installation, so inclusion on read only storage is no problem (USB stick, cd/dvd). read more...
mail this link | permapage | score:9613 | -gg234, April 30, 2013

Tutorial: Install Postfix, Courier, MySQL, SquirrelMail on CentOS 6.2

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This document describes how to install a Postfix mail server that is based on virtual users and domains, i.e. users and domains that are in a MySQL database. I'll also demonstrate the installation and configuration of Courier, so that Courier can authenticate against the same MySQL database Postfix uses. The resulting Postfix server is capable of SMTP-AUTH and TLS and quota. Passwords are stored in encrypted form in the database. In addition to that, this tutorial covers the installation of Amavisd, SpamAssassin, ClamAV and SquirrelMail. read more...
mail this link | permapage | score:9594 | -falko, February 2, 2012

Tutorial: Run Joomla 1.7 on Nginx on Debian 6, Ubuntu 11.10

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This tutorial shows how you can install and run a Joomla 1.7 web site on a Debian Squeeze or Ubuntu 11.10 system that has nginx installed instead of Apache (LEMP = Linux + nginx (pronounced "engine x") + MySQL + PHP). nginx is a HTTP server that uses much less resources than Apache and delivers pages a lot of faster, especially static files. read more...
permapage | score:9577 | -falko, December 15, 2011
More admin articles...
Abstract Art in North Florida

Selected articles

Space Tyrant: Multithreading lessons learned on SMP hardware

Why Programmers are not Software Engineers

Download: Linux 3D Client for Starship Traders

No, RMS, Linux is not GNU/Linux

Apple to Intel move no threat to Linux

Beneficial Computer Viruses

Space Tyrant: A threaded game server project in C

Hacker Haiku

Missing the point of the Mac Mini

Why software sucks

Closed Source Linux Distribution Launched

Space Tyrant: A multiplayer network game for Linux

The short life and hard times of a Linux virus

Shadow.sh: A simple directory shadowing script for Linux

Space Tyrant: A threaded C game project: First Code

Linux vs. Windows: Why Linux will win

Programming Language Tradeoffs: 3GL vs 4GL

How to install Ubuntu Linux on the decTOP SFF computer

Tutorial: Introduction to Linux files

The Supreme Court is wrong on Copyright Case

The Real Microsoft Monopoly

Linux dominates Windows

Mono-culture and the .NETwork effect

The Network Computer: An opportunity for Linux

Librenix T-Shirts and Coffee Mugs!

Microsoft to push unlicensed users to Linux

Apple DIY Repair

The life cycle of a programmer

MiniLesson: An introduction to Linux in ten commands

Testing the Digital Ocean $5 Cloud Servers with an MMORPG

Graffiti Server Download Page

VPS: Xen vs. OpenVZ

Scripting: A parallel Linux backup script

 

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Articles are owned by their authors.   © 2000-2012 Ray Yeargin