Using YUM in RHEL, CentOS, Fedora

The following article will describe how to use YUM in RHEL, CentOS and Fedora.

http://tinyurl.com/8la63w

RedHat Extends Support for RHEL

Redhat extends full support for RHEL from another one year, that means Centos also will get the same benefit.



Read the full story.

Linux Unerace Undelete Command

This is a tutorial explaining how to undelete data in Linux

http://tiny.cc/tMJGW

As explained above, We can't undelete or unerace files in Linux, But try out the following live Linux distributions, These are used for system rescue operations.

Trinity Rescue Kit - Website
SystemRescueCd - Website

26/03/2008 - I found this article on how to undelete files form ext3 file system, interesting..

Finding All Hosts on a Network

This is nice little script to find out all hosts in a Linux or a Windows network

http://tiny.cc/aYs2h

Using YUM and RPM in RedHat / Fedora / CentOS

This is a guide to learn all the things about RPM (Red Hat Package Manager)

http://docs.fedoraproject.org/drafts/rpm-guide-en

This is a guide to learn all the things about YUM (Yellow dog Updater, Modified)

http://docs.fedoraproject.org/yum/en

Adding Cron Jobs in Linux (Schedule Tasks)

Tutorial about adding cron jobs in Linux (schedule tasks)

http://tiny.cc/DsJr7

Removing Users From Groups In CentOS / RHEL / Fedora

Removing Users From Groups In CentOS / RHEL / Fedora In CLI

So many websites will explain how to add a user to a group, but if i need to remove a user from a group in the CLI how to do it, This is how..

If you don't know how to add a user to a group read the following tutorial.

http://tiny.cc/W0bzu

How to remove a user from a group.

I have not found any commands for this so I'll teach a manual method.

Assume there is a group call "group1" and there are three members in the group call "user1", "user2", "user3"

I want to remove "user2" from "group1"

1. The group details will be stored under two files call "group" and another call "gshadow", We'll examine the files first

# cat /etc/group

You'll find a line as follows

group1:x:503:user1,user2,user3

# cat /etc/gshadow

You'll find a line as follows

group1:!::user1,user2,user3

2. Now what we have to do is, manually remove "user2" from the "group1", Give the following command.

# vigr

The above command will open "/etc/group" file in VI text editor.

3. Use the down arrow key and go up to "group1:x:503:user1,user2,user3" line and press " i " to go to insert mode, and delete "user2" from the line, Now it'll look like this.

group1:x:503:user1,user3

Then press "esc" and type" :wq " to save and exit the file. It'll ask a question as follows,

You are using shadow groups on this system.
Would you like to edit /etc/gshadow now [y/n]?

Press " y " and press "enter"

Now it'll open "/etc/gshadow" file in VI text editor.

Use the down arrow key and go up to "group1:!::user1,user2,user3" line and press " i " to go to insert mode, and delete "user2" from the line, Now it'll look like this.

group1:!::user1,user3

Then press "esc" and type" :wq " to save and exit the file.

4. That's it, now the "user2" is removed from "group1"

This is another way to do it but you want be able to completely remove a user from the groups he/she belong to.

http://tiny.cc/zMm7x

Controlling Services In Linux

In a Linux box lot of services will be started during the startup, but we may not need all the services automatically getting started. We can turn off the unwanted services and make our system faster.

1. Read the following tutorial and get an idea about Linux services, although it's written for fedora, all these services will be similar in all Linux systems.

http://www.mjmwired.net/resources/mjm-services-f8.html

2. Controlling

In Ubuntu, RedHat, Fedora, CentOS (GUI)

Go to System -> Administration -> Services -> Unselect unwanted services

In Redhat, Fedora, CentOS (CLI)

# chkconfig servicename off

If you want to turn the service on again

# chkconfig servicename on

Or type

# ntsysv

And using the space bar you can select or unselect the services.

A Cool Fedora Story

You have to read this, It's a story about how to contribute software packages in to Fedora project. Fedora is the community OS release of RHEL.

http://www.redhatmagazine.com/2008/02/28/when-sally-met-eddie-the-fedora-package-story

Accessing Windows partitions from Linux

By default any Linux system will fully support FAT partitions, But when it comes to NTFS some are still NOT supporting by default.

Desktop Editions such as Ubuntu 7.10 and Fedora 8 now fully supporting NTFS (with write support), and the partitions are automatically mounted.

Server Editions such as CentOS 5 and RHEL 5 you have to do the following to access NTFS partitions.

1. Configure RPMFroge 3rd party repository, Please read my tutorial about CentOS Repositories.

2. Install the following packages

# yum install dkms-fuse fuse-ntfs-3g

Accessing the Windows partitions.

1. See what are the current partitions in your system, and figure out what partitions belongs to windows.

# fdisk -l

Usually NTFS partitions will be displayed with a HPFS/NTFS label, Where as FAT partitions will be labeled as W95 FAT32 or W95 FAT16

In the example I'm assuming,

/dev/hda1 = NTFS
/dev/hda2 = FAT32

2. Create mount points for each windows partition that you have in the system.

# mkdir /media/ntfs
# mkdir /media/fat32

check

# ls -l /media

Note - The mount piont name can be any name that you like.

3. Manually mounting the partitions.

FAT

# mount /dev/hda2 /media/fat32
# cd /media/fat32
# ls -l

Note - You'll be having Read/Write access to FAT partitions.

NTFS

# mount -t ntfs-3g /dev/hda1 /media/ntfs
# cd /media/ntfs
# ls -l

Note - You'll be having Read/Write access to NTFS partitions.

Once you manually mount the partitions, when you shutdown your PC the partitions will be automatically unmounted.

4. Automatically mounting the partition on boot.

# nano /etc/fstab

at the end of file, enter the following lines.

/dev/hda1 /media/ntfs ntfs-3g defaults 0 0
/dev/hda2 /media/fat vfat defaults 0 0

What we have done is, first we give the partition number then the mount point then the file system then the permissions then whether to check the partition in case of a power failure, 0 (zero) means don't check since we don't have necessary tools to check NTFS or FAT partitions and finally the checking priority.

4. So now every time you boot your PC the partitions will be automatically mounted to the mount points.

Installing Adobe Flash Plugin for Firefox in Redhat / CentOS / Fedora

For 32 bit users

1. Go to Adobe Flash Plugin web site, Follow the instructions under option 3 " YUM REPOSITORY INSTALLATION"

Web site - http://www.adobe.com/shockwave/download/download.cgi?P1_Prod_Version=ShockwaveFlash

For 64 bit users

1. Install the nspluginwrapper.i386 package to enable the 32-bit Adobe Flash plugin in x86_64 Firefox and the pulseaudio-libs.i386 package to enable sound from the plugin.

2. Create the 32bit mozilla plugin directory using this command.

# mkdir -p /usr/lib/mozilla/plugins

3. Install the nspluginwrapper.i386, nspluginwrapper.x86_64, and pulseaudio-libs.i386 packages.

# yum -y install nspluginwrapper.{i386,x86_64} pulseaudio-libs.i386

4. Install flash-plugin as shown in 32 bit section above.

5. Run mozilla-plugin-config to register the flash plugin.

# mozilla-plugin-config -i -g -v

6. Close all Firefox windows, and then relaunch Firefox.

7. Type about:plugins in the URL bar to ensure the plugin is loaded.

NOTE - The following was adapted from the Fedora 8 Release Notes. The 64 bit instructions may NOT work for RHEL 5 and CentOS 5.

Special Thanks to Fedora Documentation Team and Mauriat Miranda

Installing Additional Multimedia Codecs In RedHat / CentOS

READ following post.
http://tr.im/centcodecs

Using CentOS 5 Repos in RHEL 5 Server

1. Remove "yum-rhn-plugin" package from RHEL, this is used to check the activation in RHEL.

# rpm -e yum-rhn-plugin

2. Remove the "redhat-release" related packages, this is used to check the repositories compatibility. usually we can't remove these packages because they are used by other packages of the system for proper fuctioning. so we'll use the "--nodeps" parameter to forcely remove them from the system.

# rpm -e redhat-release-notes-5Server redhat-release-5Server --nodeps

3. Download & install the "centos-release" relates packages, to fill in the gap that we made by removing the "redhat-release" related packages.

i386 (32 bit)
http://mirrors.nl.kernel.org/centos/5/os/i386/CentOS/centos-release-5-2.el5.centos.i386.rpm
http://mirrors.nl.kernel.org/centos/5/os/i386/CentOS/centos-release-notes-5.2-2.i386.rpm

x86_64 (64 bit)
http://mirrors.nl.kernel.org/centos/5/os/x86_64/CentOS/centos-release-5-2.el5.centos.x86_64.rpm
http://mirrors.nl.kernel.org/centos/5/os/x86_64/CentOS/centos-release-notes-5.2-2.x86_64.rpm

4. To automatically inform about the updates in GUI, Do the following.

# nano /etc/yum/yum-updatesd.conf

In the file, type as follows under the section "# how to send notifications"

dbus_listener = yes

5. To change the OS name in the CLI login, Do the following.

# nano /etc/issue

Since we have installed the "centos-release" relates packages, the OS name will come as "CentOS release 5 (Final)", so delete it and type

Red Hat Enterprise Linux Server release 5 (Tikanga)

Or any name you like.

6. Now your system is ready.

7. Read my guide on "CentOS Repositories"

CentOS Repositories

What is a Repository?

A software repository (sometimes abbreviated as a repo) is a storage location from which software packages may be retrieved and installed on a computer. Many software publishers and other organizations maintain servers on the Internet for this purpose, either free of charge or for a subscription fee.

CentOS Software Repositories ( Official )

Base repo - The packages that comes with the release media. ( CDs or the DVD )

Addons repo - The packages used/produced in the build but not released with the release media

Extras repo - The additional packages that may be useful

Updates repo - The updated packages of the above repos

Centosplus repo - This repository is for items that actually upgrade certain base CentOS components. This repo will change CentOS to not be exactly like the upstream providers content

Website - http://mirror.centos.org/centos-5/5

The above Base repo, Addons repo, Extras repo, Updates repo are 100% compatible with RHEL, where as Centosplus repo is NOT 100% compatible with RHEL, so by default it's disabled.

CentOS Software Repositories ( 3rd Party )

**NOT maintained by official OS developers, but contains lots of helpful packages, 100% compatible with RHEL and CentOS.

RPMForge repo - This repository is a collaboration of Dag, Dries, and other packagers. They provide over 2600 packages for CentOS

Website - http://dag.wieers.com/rpm/packages.php

Fedora Extra Packages for Enterprise Linux (EPEL) repo - This repository provides rebuilds of Fedora packages for RHEL4 and RHEL5

Website for i386 packages - http://download.fedora.redhat.com/pub/epel/5/i386/repoview
Website for x64 packages - http://download.fedora.redhat.com/pub/epel/5/x86_64/repoview

How to use the CentOS Repositories?

In CentOS and RHEL to use the repositories we have to use a software management tool call "YUM" ( Yellow dog Updater, Modified ), the tool needs the repository information to manage software within your system. The information about the official repositories comes by default with YUM, but information about 3rd party repositories we have to manually configure.

The location of the repository information

# cd /etc/yum.repos.d
# ls -l

-rw-r--r-- 1 root root 2049 Nov 23 07:02 CentOS-Base.repo
-rw-r--r-- 1 root root 622 Nov 23 07:02 CentOS-Media.repo

CentOS-Base.repo file contains the information about the official CentOS repositories. To use the repos you have to have a live Internet connection.

CentOS-Media.repo file contaions the information about the packages included in the official CDs or the DVD, This you can use if you don't have internet.

How to use 3rd party Repositories?

You have to be careful, because in the 3rd party repos we might find packages that are already present in the official repos, we have to make sure we are NOT overlapping the packages, so this is how to do it.

1. Install "yum-priorities" plugin for YUM, this plugin will help you to prioritize the each repository that you use in the system, so we can give a high priority to official repositories and low priority to 3rd party repositories, so the packages in the 3rd party repos won't overlap the packages in the official repos.

# yum install yum-priorities

2. Then open the official yum repo information file

# nano /etc/yum.repos.d/CentOS-Base.repo

3. At the end of each heading, put like this

[base]
.
.
.
priority=1

[updates]
.
.
.
priority=1

[addons]
.
.
.
priority=1

[extras]
.
.
.
priority=1

[centosplus]
.
.
.
priority=2

What we have done above is, we have given priority=1 to [base], [updates], [addons] and [extras] repositories and priority=2 to [centosplus] repository, so [centosplus] repository packages won't overlap with [base], [updates], [addons] and [extras] repository packages.

4. Then we can install 3rd party repositories, first we'll configure RPMForge repo. All 3rd party repos can be configured by installing their release RPM. So to configure RPMForge, download and install the following packages.

for i386 - http://apt.sw.be/redhat/el5/en/i386/RPMS.dag/rpmforge-release-0.3.6-1.el5.rf.i386.rpm

for x64 - http://apt.sw.be/redhat/el5/en/x86_64/RPMS.dag/rpmforge-release-0.3.6-1.el5.rf.x86_64.rpm

5. Then check the location of the repository information and edit the rpmforge.repo file as follows.

# cd /etc/yum.repos.d
# ls -l

-rw-r--r-- 1 root root 2049 Nov 23 07:02 CentOS-Base.repo
-rw-r--r-- 1 root root 622 Nov 23 07:02 CentOS-Media.repo
-rw-r--r-- 1 root root 684 Mar 8 2007 mirrors-rpmforge
-rw-r--r-- 1 root root 428 Mar 8 2007 rpmforge.repo

# nano rpmforge.repo

[rpmforge]
.
.
.
priority=11

When we do this, the packages in RPMForge won't overwire packages in our official repos.

6. Then we'll install Fedora Extra Packages for Enterprise Linux (EPEL) repo, download and install the following package.

for i386 / x86_64 - http://download.fedora.redhat.com/pub/epel/5/i386/epel-release-5-2.noarch.rpm

7. Then check the location of the repository information and edit the epel.repo file as follows.

# cd /etc/yum.repos.d
# ls -l

-rw-r--r-- 1 root root 2049 Nov 23 07:02 CentOS-Base.repo
-rw-r--r-- 1 root root 622 Nov 23 07:02 CentOS-Media.repo
-rw-r--r-- 1 root root 954 Apr 3 2007 epel.repo
-rw-r--r-- 1 root root 771 Apr 3 2007 epel-testing.repo
-rw-r--r-- 1 root root 684 Mar 8 2007 mirrors-rpmforge
-rw-r--r-- 1 root root 428 Mar 8 2007 rpmforge.repo

# nano epel.repo

[epel]
.
.
.
priority=12

When we do this, the packages in Fedora Extra Packages for Enterprise Linux (EPEL) repo won't overwire packages in RPMForge repo or official repos.

8. Now your system ready to manage software packages.

Firestarter for CentOS5 / RHEL5

Firestarter is an open source visual firewall program. The software aims to combine ease of use with powerful features, therefore serving both Linux desktop users and system administrators.

More information - www.fs-security.com
Documentation - www.fs-security.com/docs.php

Download 1386 RPM for RHEL5 or CentOS5 (32 bit)

Download x86_64 RPM for RHEL5 or CentOS5(64 bit)

Microsoft fonts for Fedora/Redhat/Centos

Download Microsoft core fonts RPM that includes fonts in XP/Vista

http://avi.alkalay.net/software/webcore-fonts

Custom GRUB splash image in Fedora/Redhat/Centos

• Log or Switch in to the root account

• Get an image file to use for the new splash image (can be some wallpaper in jpg, png format)
  

• Check whether ImageMagick rpm is installed

# rpm -q ImageMagick

• If it's not installed you have to install it first

# yum -y install ImageMagick

• Then, Assuming the image is in the root's home folder & the image name is "myboot.jpg"

# cd
# convert myboot.jpg -resize 640x480! -colors 14 -depth 8 myboot.xpm
# ls

• Now you will be able to see a file call "myboot.xpm"

• Then you have to gzip it.

# gzip myboot.xpm
# ls

• Now you will be able to see a file call "myboot.xpm.gz"

• Then you have to copy it to "/boot/grub" folder

# cp myboot.xpm.gz /boot/grub

• Then you have to edit "grub.conf" file with your favorite text editor, I'll use "nano" text editor

# nano /etc/grub.conf

Edit the following line

splashimage=(hd0,0)/grub/splash.xpm.gz

to

splashimage=(hd0,0)/grub/myboot.xpm.gz

NOTE- DON'T EDIT ANYOTHER PARAMETER OF THE LINE, ONLY CHANGE THE IMAGE FILE NAME.

save & exit

• Then reboot your system

# reboot

• Then you'll be able to see the new GRUB spalsh image during the startup.

Is Red Hat still relevant

A nice article about RedHat role in the Linux world

http://www.montanalinux.org/redhat-relevent.html