20 reasons you should switch to Linux

The fact Linux is free remains its biggest draw, but there’s much more to it than that

There are hundreds of compelling reasons why Linux is better than all the rival operating systems. Here are just 20.

1. Linux is free

No matter how many computers you install it on, the cost of Linux remains the same: zero.

In these days of multi-computer households, this can be a massive saving, especially when you consider the cost of all the programs you have to add to a standard Windows installation. Continue reading

Configuring VNC Server Access on a Redhat Linux

1. Introduction

Most of the time as a system administrator you are managing your servers over the network. It is very rare that you will need to have a physical access to any of your managed servers. In most cases all you need is to SSH remotely to do your administration tasks. In this article we will configure a GUI alternative to a remote access to your RHEL server, which is VNC. VNC allows you to open a remote GUI session to your server and thus providing you with a full graphical interface accessible from any remote location.

2. Installation of VNC server

In order to enable an access to our Redhat Linux system using VNC we first need to install it. Make sure that you have your repository enabled and execute the command:

# yum install tigervnc-server Continue reading

Creating a Redhat package repository

1. Introduction

If your Redhat server is not connected to the official RHN repositories, you will need to configure your own private repository which you can later use to install packages. The procedure of creating a Redhat repository is quite simple task. In this article we will show you how to create a local file Redhat repository as well as remote HTTP repository.

2. Using Official Redhat DVD as repository

After default installation and without registering your server to official RHN repositories your are left without any chance to install new packages from redhat repository as your repository list will show 0 entries: Continue reading

Configuring Gmail as a Sendmail email relay

1. Introduction

In this configuration tutorial we will guide you through the process of configuring sendmail to be an email relay for your gmail or google apps account. This allows you to send email from your bash scripts, hosted website or from command line using mail command. Other examples where you can utilize this setting is for a notification purposes such or failed backups etc. Sendmail is just one of many utilities which can be configured to rely on gmail account where the others include postfix, exim , ssmpt etc. In this tutorial we will use Debian and sendmail for this task.

2. Install prerequisites

# apt-get install sendmail mailutils sendmail-bin Continue reading

Clear memory cache on your Linux server

There may be a time that you wish to clear a Memory on your server. Normally you do not want to fiddle with it so do it only you are sure that it is necessary and that it would not affect your server’s performance. For this we can use sysctl command which allows linux admins to configure kernel parameters at runtime.

This command will clear pagecache:

/sbin/sysctl vm.drop_caches=1

To clear dentries and inodes you can use:

/sbin/sysctl vm.drop_caches=2

To free memory of the all above use a following command:

/sbin/sysctl vm.drop_caches=3

What the above commands will do is that they will sync your memory and edit a following file with appropriate number entry. :

/proc/sys/vm/drop_caches

Do not edit this file directly !

Use top utility to see whether you successfully freed your memory.

Clear memory cache on your Linux server

There may be a time that you wish to clear a Memory on your server. Normally you do not want to fiddle with it so do it only you are sure that it is necessary and that it would not affect your server’s performance. For this we can use sysctl command which allows linux admins to configure kernel parameters at runtime.

This command will clear pagecache:

/sbin/sysctl vm.drop_caches=1

To clear dentries and inodes you can use:

/sbin/sysctl vm.drop_caches=2 Continue reading

setup as an step by step guide to install, configure and maintain OpenLDAP

» What is LDAP?

LDAP stands for Lightweight Directory Access Protocol, a way to describe directory contents as separated records (entries). These entries consist of a collection of attributes, all with a globally-unique key, the Distinguished Name (DN). The DN consists of smaller pieces, describing the entity.
Examples (with naming attribute): user (cn), group (cn), computer (cn), container (cn), organizational unit (ou), domain (dc).
LDAP is based on the DAP X.500 standard (created at the University of Michigan), but with the goal to be “simple”. The X.500 standard is very extensive and often too complex for smaller needs, that’s why a light version of DAP was created. Continue reading

Linux Find FC ID (WWN) of a disk/LUN

If your server is connected to more than two SANs of the same type it is really hard to find what disk is on what SAN and how it is connected to your server. You can get the Fiber Channel addresses of the HBAs by typing the following commands:
# systool -c fc_host -v
Type the following command to determine the fibre channel target WWN:
# systool -c fc_transport -v
You will get node name (FC WWN) and port name of the storage processor port. Type the following command, to determine the mapping between SCSI HBTL addresses and the disks:

# sg_map -x

See sg_map and systool command man page for more details.

Pxe Server on Rhel5

PXE(Pre-eXecution Environment)On
Rhel5.x Versions

Requirements and network orienation for this setup
#PXE Enabled NIC/LAN Card & set as network booting in Client BIOS.
#Configure the network (NFS,FTP,HTTP)Server to export the installation tree.
#Configure DHCP server.
#A TFTP server necessary for PXE booting .
Pacakges required!!
# tftp-server-*
# tftp-client-* (for testing)
# dhcp-*
# xinetd-*
# system-config-netboot-*
I am going to share my lab setup for same.

In my lab I have installed rhel5.4 server as following details
/boot <============>100MB
/ <============>2000MB
Swap <============>4000MB double of my system memory
/home<============>3000MB
/var <============>5000MB
My server ip address is 192.168.0.254/255.255.255.0
This server acting as NFS,TFTP,DHCP.

Continue reading

New Red Hat OpenStack Admin course

Red Hat Open StackOpenStack is quickly becoming one of the largest cloud computing platforms, and it’s also free and open source software. Red Hat Vice President of Cloud and Virtualization Development has been singing the praises of the project on the Red Hat blog, and Red Hat have just recently launched a brand new course in OpenStack Administration.

The course, code CL210, promises to teach you how to “Install, configure, and maintain a cloud computing environment using Red Hat OpenStack”. This includes such skills as:

Install Red Hat OpenStack using packstack.

Use horizon to manage Red Hat OpenStack.

Manage keystone, glance, nova, nova network, and cinder.

Provide redundancy for each service.

For mode details refer to page “Red Hat OpenStack Training & Certification” page of Focus Training Services.