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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:9696 | -nixcraft, December 14, 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:9664 | -Ray, January 25, 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:9648 | -falko, December 23, 2012

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:9616 | -Ray, March 24, 2011

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:9610 | -nixcraft, November 21, 2012

ATA over Ethernet (AoE) (Ubuntu 12.04)

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This guide explains how you can set up an AoE target and an AoE initiator (client), both running Ubuntu 12.04. AoE stands for "ATA over Ethernet" and is a storage area network (SAN) protocol which allows AoE initiators to use storage devices on the (remote) AoE target using normal ethernet cabling. "Remote" in this case means "inside the same LAN" because AoE is not routable outside a LAN (this is a major difference compared to iSCSI). To the AoE initiator, the remote storage looks like a normal, locally-attached hard drive. read more...
mail this link | permapage | score:9604 | -falko, October 19, 2012

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:9586 | -falko, June 7, 2013

Migrate Mailboxes between IMAP Servers with imapcopy

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This guide explains how you can migrate mailboxes between IMAP servers with imapcopy. imapcopy lets you copy recursively all email messages and folders from one imap account to another. It supports the protocols imap and imaps. read more...
permapage | score:9584 | -falko, October 7, 2011

Server monitoring with Icinga (Debian 6)

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Icinga is an enterprise grade open source monitoring system which keeps watch over networks and any conceivable network resource, notifies the user of errors and recoveries and generates performance data for reporting. It is a fork of Nagios. This tutorial explains how to install Icinga on a Debian Squeeze server to monitor this server and another Debian Squeeze server. read more...
permapage | score:9581 | -falko, August 25, 2011

How to install Ubuntu Linux on the decTOP SFF computer

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I recently bought a decTOP small form factor (SFF) computer. My goal was to build a cheap, fanless, quiet, and low power consumption Linux server. For $99 plus the cheapest available shipping, $40, my machine arrived 11 days after I placed the order.

This is a tiny computer, about the size of a Mac Mini. But, because it has no fan, it runs a bit quieter and, with the help of a 1-watt, 366 MHz CPU, consumes only 8 watts. For comparison, the G4 Mac Mini consumes about 20-30 watts, depending on load.

The decTOP comes with 128 MB of RAM in its sole SO-DIMM slot and a 10 GB 3.5 inch hard drive. I understand that it's a simple matter to replace the drive and to upgrade the memory to a maximum of 512MB.

It also comes with no operating system and the ability to boot only from a USB drive. This article details the steps I used to build the USB boot/installation drive and install Ubuntu 6.06 on the decTOP.

There is another article -- with additional decTOP links -- here on installing Ubuntu 6.06 on the decTOP with the aid of a Windows system. Fortunately ;), I run Mac OS X and Linux (Ubuntu 7.04), so that article didn't work for me. I did the installation of the Ubuntu 6.06 LTS Server Edition using my Ubuntu Linux box and a 1 GB USB flash drive -- although a 512 MB USB drive should work as well.

  1. Download the Ubuntu 6.06 server ISO image from the Ubuntu download page. Depending on your plans for the decTOP, you might want to choose the desktop version. Unless you have already upgraded your decTOP's memory, however, you'll want to stick with the 6.06 releases.

  2. Install the mbr, mtools, and syslinux packages on the Linux system you'll be using to prepare the USB drive. If you run Ubuntu or some other Debian-derived system, the following commands may do the work for you.
    apt-get install mbr
    apt-get install mtools
    apt-get install syslinux
  3. Partition the USB drive with a single FAT-16 partition. I used the fdisk 'n' command to make the new primary partition 1. The fdisk 't' command can be used to change the partition type to FAT-16. My device name was /dev/sda.
    fdisk /dev/sda
  4. Make the FAT-16 partition the active partition. I used the fdisk 'a' command.

  5. Install a master boot record on the USB drive.
    install-mbr /dev/sda
  6. Install syslinux on the USB drive. Note that the USB drive should not be mounted when you do this.
    syslinux -s /dev/sda1
  7. Create a mountpoint and mount the ubuntu ISO image using the loopback device.
    mkdir /iso
    mount -o loop -t iso9660 ubuntu.iso /iso
  8. Create a mountpoint and mount the USB flash drive.
    mkdir /usb
    mount /dev/sda1 /usb
  9. Copy the contents of the ISO image to the USB drive. This will take some time.
    cd /iso
    cp -r . /usb/
  10. Copy the /usb/dists/dapper directory into a new /usb/dists/stable directory.
    cd /usb/dists/
    cp -r dapper/* stable
  11. Copy several files from /usb/install to the /usb root directory.
    cp /usb/install/vmlinuz /usb/
    cp /usb/install/mt86plus /usb/
    cp /usb/install/initrd.gz /usb/
  12. Install the following text into a file named syslinux.cfg in the /usb root directory.
    default vmlinuz
    append initrd=initrd.gz ramdisk_size=24000 root=/dev/ram rw
  13. Flush all writes, unmount, and remove the USB drive. After the sync step, wait for all of the data to be written to the USB drive.
    sync;sync
    umount /usb
  14. Connect the ethernet adapter to the decTOP and connect it to your network to allow automatic configuration of the network interface.

  15. Insert the USB drive into the decTOP and power it up. The decTOP should automatically boot from the USB drive and start the Ubuntu installation.

  16. Answer only the first two questions concerning language selection and go to the next step, below.

  17. Press Alt-F2 (hold down the Alt key and press the F2 function key) to open a shell. Then press enter to start the shell.

  18. Create a /cdrom and a /dev/cdroms directory in the installation ramdisk
    mkdir /cdrom /dev/cdroms
  19. Go to the /dev/cdroms directory and build a symlink from /dev/sda1 (that is likely the device name of your USB boot partition) to /dev/cdroms/cdrom0.
    cd /dev/cdroms
    ln -s ../sda1/cdrom0
  20. While still in the shell, mount the USB drive to mimic an installation CD-ROM.
    mount -t vfat /dev/cdroms/cdrom0 /cdrom
  21. Return to the installation program with Alt-F1 and continue the installation.

From this point, the process should be identical to a routine CD-ROM installation.

For a grand total of $140 and 8 watts of power consumption, I now have a near-silent Linux server running 24/7. You can telnet to it here and marvel at its blinding speed running a 250,000-sector Space Tyrant game.

mail this link | permapage | score:9568 | -Ray, August 16, 2007 (Updated: April 26, 2011)

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:9563 | -falko, April 17, 2013

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:9556 | -falko, June 6, 2013

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:9549 | -falko, May 5, 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:9541 | -Boris Derzhavets, December 31, 2011

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:9540 | -Silver Moon, August 13, 2013

How to install ajenti (like Webmin) on ubuntu 13.04 server

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Ajenti is a simple open source web based administration tool for managing ubuntu servers and this is similar to webmin.This is having nealy 35 plugins to monitor different servers (Including HTTP,DNS etc). read more...
permapage | score:9524 | -gg234, July 5, 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:9522 | -falko, June 27, 2013

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:9517 | -falko, September 12, 2012

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:9508 | -falko, April 29, 2012

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:9491 | -gg234, April 30, 2013
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Articles are owned by their authors.   © 2000-2012 Ray Yeargin