How to: Apache authentication using LDAP Server

Posted on in Categories Apache, Linux, UNIX last updated October 31, 2007

Network administrators frequently use the Lightweight Directory Access Protocol (LDAP) to implement a centralized directory server. You can use LDAP to authenticate users in Apache. Two popular open source LDAP solutions are OpenLDAP and Red Hat Directory Server. According to the Apache documentation, Novell LDAP and iPlanet Directory Server are also supported. This article focuses on OpenLDAP, but the concepts and examples should be applicable to the others.

=> Apache authentication and authorization using LDAP

How to: Linux Play DivX .avi video codec file

Posted on in Categories Debian Linux, Linux, Linux desktop, Linux distribution, Ubuntu Linux last updated September 2, 2012

From my mail bag:

I’ve downloaded .avi files which is compressed into small sizes while maintaining relatively high visual quality using DivX format. How do I play DivX compressed files under Debian / Ubuntu Linux?

The current version of the DivX Community Codec for the Windows platform is version 6.6, and for Mac OS X is 6.6x. There is no Linux version available however with the help of VLC and DivX for Linux codec, you should able to play all sort of DivX files.

Download and Install DivX Linux Codec

Open terminal and type the following command to download DivX codec:
$ cd /tmp
$ wget

Untar DivX 6.1.1 codec for Linux:
$ tar -zxvf divx611-20060201-gcc4.0.1.tar.gz
Install divx611 codec:
$ cd divx611-20060201-gcc4.0.1
$ sudo ./

Press Q after reading agreement, please type yes to install codes.

Install vlc player

The VLC media player can be installed using apt-get command, type:
$ sudo apt-get update
$ sudo apt-get install vlc

How do I play files?

Open VLC player by Visiting Applications > Sound and Video > VLC Player. You can also open terminal and type the command:
$ vlc /path/to/my-downloaded-movie.avi

Further readings:

CentOS / Red Hat Linux: Install and manage iSCSI Volume

Posted on in Categories Backup, CentOS, Linux, RedHat/Fedora Linux, Storage last updated February 18, 2011

Internet SCSI (iSCSI) is a network protocol s that allows you to use of the SCSI protocol over TCP/IP networks. It is good alternative to Fibre Channel-based SANs. You can easily manage, mount and format iSCSI Volume under Linux. It allows access to SAN storage over Ethernet.

Open-iSCSI Project

Open-iSCSI project is a high-performance, transport independent, multi-platform implementation of iSCSI. Open-iSCSI is partitioned into user and kernel parts.

Instructions are tested on:
[a] RHEL 5
[b] CentOS 5
[c] Fedora 7
[d] Debian / Ubuntu Linux

Install Required Package

iscsi-initiator-utils RPM package – The iscsi package provides the server daemon for the iSCSI protocol, as well as the utility programs used to manage it. iSCSI is a protocol for distributed disk access using SCSI commands sent over Internet Protocol networks. This package is available under Redhat Enterprise Linux / CentOS / Fedora Linux and can be installed using yum command:
# yum install iscsi-initiator-utils

A note about Debian / Ubuntu Linux

If you are using Debian / Ubuntu Linux install open-iscsi package, enter:
$ sudo apt-get install open-iscsi

iSCSI Configuration

There are three steps needed to set up a system to use iSCSI storage:

  1. iSCSI startup using the init script or manual startup. You need to edit and configure iSCSI via /etc/iscsi/iscsid.conf file
  2. Discover targets.
  3. Automate target logins for future system reboots.
  4. You also need to obtain iSCSI username, password and storage server IP address (target host)

Step # 1: Configure iSCSI

Open /etc/iscsi/iscsid.conf with vi text editor:
# vi /etc/iscsi/iscsid.conf
Setup username and password:
node.session.auth.username = My_ISCSI_USR_NAME
node.session.auth.password = MyPassword
discovery.sendtargets.auth.username = My_ISCSI_USR_NAME
discovery.sendtargets.auth.password = MyPassword


  • node.session.* is used to set a CHAP username and password for initiator authentication by the target(s).
  • discovery.sendtargets.* is used to set a discovery session CHAP username and password for the initiator authentication by the target(s)

You may also need to tweak and set other options. Refer to man page for more information. Now start the iscsi service:
# /etc/init.d/iscsi start

Step # 2: Discover targets

Now use iscsiadm command, which is a command-line tool allowing discovery and login to iSCSI targets, as well as access and management of the open-iscsi database. If your storage server IP address is, enter:
# iscsiadm -m discovery -t sendtargets -p
# /etc/init.d/iscsi restart

Now there should be a block device under /dev directory. To obtain new device name, type:
# fdisk -l
# tail -f /var/log/messages

Oct 10 12:42:20 ora9is2 kernel:   Vendor: EQLOGIC   Model: 100E-00           Rev: 3.2 
Oct 10 12:42:20 ora9is2 kernel:   Type:   Direct-Access                      ANSI SCSI revision: 05
Oct 10 12:42:20 ora9is2 kernel: SCSI device sdd: 41963520 512-byte hdwr sectors (21485 MB)
Oct 10 12:42:20 ora9is2 kernel: sdd: Write Protect is off
Oct 10 12:42:20 ora9is2 kernel: SCSI device sdd: drive cache: write through
Oct 10 12:42:20 ora9is2 kernel: SCSI device sdd: 41963520 512-byte hdwr sectors (21485 MB)
Oct 10 12:42:20 ora9is2 kernel: sdd: Write Protect is off
Oct 10 12:42:20 ora9is2 kernel: SCSI device sdd: drive cache: write through
Oct 10 12:42:20 ora9is2 kernel:  sdd: unknown partition table
Oct 10 12:42:20 ora9is2 kernel: sd 3:0:0:0: Attached scsi disk sdd
Oct 10 12:42:20 ora9is2 kernel: sd 3:0:0:0: Attached scsi generic sg3 type 0
Oct 10 12:42:20 ora9is2 kernel: rtc: lost some interrupts at 2048Hz.
Oct 10 12:42:20 ora9is2 iscsid: connection0:0 is operational now

/dev/sdd is my new block device.

Step # 3: Format and Mount iSCSI Volume

You can now partition and create a filesystem on the target using usual fdisk and mkfs.ext3 commands:
# fdisk /dev/sdd
# mke2fs -j -m 0 -O dir_index /dev/sdd1

# mkfs.ext3 /dev/sdd1

Tip: If your volume is large size like 1TB, run mkfs.ext3 in background using nohup:
# nohup mkfs.ext3 /dev/sdd1 &

Mount new partition:
# mkdir /mnt/iscsi
# mount /dev/sdd1 /mnt/iscsi

Step #4: Mount iSCSI drive automatically at boot time

First make sure iscsi service turned on at boot time:
# chkconfig iscsi on
Open /etc/fstab file and append config directive:
/dev/sdd1 /mnt/iscsi ext3 _netdev 0 0
Save and close the file.

Further readings:

Linux assembly language comparison: GNU Assembler (GAS) vs Netwide Assembler (NASM)

Posted on in Categories Howto, Linux, programming, UNIX last updated November 6, 2007

This article explains some of the more important syntactic and semantic differences between two of the most popular assemblers for Linux®, GNU Assembler (GAS) and Netwide Assembler (NASM), including differences in basic syntax, variables and memory access, macro handling, functions and external routines, stack handling, and techniques for easily repeating blocks of code.

Unlike other languages, assembly programming involves understanding the processor architecture of the machine that is being programmed. Assembly programs are not at all portable and are often cumbersome to maintain and understand, and can often contain a large number of lines of code. But with these limitations comes the advantage of speed and size of the runtime binary that executes on that machine. Even though the differences between these two assemblers are substantial, it’s not that difficult to convert from one form to another. You might find that the AT&T syntax seems at first difficult to understand, but once mastered, it’s as simple as the Intel syntax.

=> Linux Assemblers: A Comparison of GAS and NASM