Basado en paquetes de RHEL v4 / 5 .. antes que nada debemos importar las llaves , como es logico como root :

rpm --import http://dag.wieers.com/packages/RPM-GPG-KEY.dag.txt
rpm --import http://dries.ulyssis.org/ayo/RPM-GPG-KEY.dries.txt
rpm --import http://freshrpms.net/packages/RPM-GPG-KEY.txt

y luego modificar o practicamente actualizar (copiar todo esto en el archivo yum.conf)

* OBS , para Centos 4 , cambiar 5 por 4 , para 64 bits , solo i386 por x86_64

el archivo sera el siguiente :

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[main]
retries = 20
tolerant = 1
cachedir = /var/cache/yum
exactarch = 1
pkgpolicy = newest
distroverpkg = redhat-release
debuglevel = 2
logfile = /var/log/yum.log
[centos updates]
gpgcheck = True
enabled = 1
name = CenOS Updates
baseurl = http://mirror.centos.org/centos/5/updates/i386/
http://mirror.centos.org/centos/5/updates/i386/
http://public.planetmirror.com/pub/caosity/centos/5/updates/i386/
http://public.planetmirror.com/pub/caosity/centos/5/updates/i386/
[dries]
gpgcheck = True
enabled = 0
name = Extra CentOS rpms dries - EL$releasever - $basearch
baseurl = http://apt.sw.be/dries/redhat/el5/en/i386/dries/
http://apt.sw.be/redhat/el5/en/i386/dag/
[dag]
name = Dag
enabled = 0
baseurl = http://dag.freshrpms.net/redhat/el5/en/$basearch/dag/
http = //ftp.heanet.ie/pub/freshrpms/pub/dag/redhat/el5/en/$basearch/dag/
gpgcheck = True
[jpackage-fedora]
name = JPackage CentOS Packages
failovermethod = priority
enabled = 0
baseurl = http://mirrors.sunsite.dk/jpackage/1.6/redhat-el-5.0/free
ftp://jpackage.hmdc.harvard.edu/JPackage/1.6/redhat-el-5.0/free
http://sunsite.informatik.rwth-aachen.de/ftp/pub/Linux/jpackage/redhat-el-5.0/free
gpgcheck = True
[centos base]
gpgcheck = True
enabled = 1
name = CenOS Base
baseurl = http://mirror.centos.org/centos/5/os/i386/
http://mirror.centos.org/centos/5/os/i386/
http://public.planetmirror.com/pub/caosity/centos/5/os/i386/
http://public.planetmirror.com/pub/caosity/centos/5/os/i386/
[dag apt]
gpgcheck = True
enabled = 1
name = Dag APT Repository
baseurl = http://dag.freshrpms.net/redhat/el5/en/i386/dag/
http://apt.sw.be/redhat/el5/en/i386/dag/
[flash]
gpgcheck = True
enabled = 0
name = macromedia.mplug.org - Flash Plugin
baseurl = http://macromedia.mplug.org/apt/redhat/5
http://sluglug.ucsc.edu/macromedia/apt/redhat/5
http://ruslug.rutgers.edu/macromedia/apt/redhat/5
http://macromedia.rediris.es/apt/redhat/5
[centos addons]
gpgcheck = True
enabled = 1
name = CenOS Addons
baseurl = http://mirror.centos.org/centos/5/addons/i386/
http://mirror.centos.org/centos/5/addons/i386/
http://public.planetmirror.com/pub/caosity/centos/5/addons/i386/
http://public.planetmirror.com/pub/caosity/centos/5/addons/i386/
[jpackage-generic]
name = JPackage Cross-Platform Packages
failovermethod = priority
enabled = 0
baseurl = http://mirrors.sunsite.dk/jpackage/1.6/generic/free
ftp://jpackage.hmdc.harvard.edu/JPackage/1.6/generic/free
http://sunsite.informatik.rwth-aachen.de/ftp/pub/Linux/jpackage/1.6/generic/free
gpgcheck = True
[centos extras]
gpgcheck = True
enabled = 1
name = CenOS Extras
baseurl = http://mirror.centos.org/centos/5/extras/i386/
http://mirror.centos.org/centos/5/extras/i386/
http://public.planetmirror.com/pub/caosity/centos/5/extras/i386/
http://public.planetmirror.com/pub/caosity/centos/5/extras/i386/
[pidgin]
name=Pidgin for RHEL/CentOS $releasever - $basearch
baseurl=http://rpm.pidgin.im/centos/$releasever/$basearch/
enabled=1
gpgcheck=1
gpgkey=http://rpm.pidgin.im/RPM-GPG-KEY-pidgin

[pidgin-debuginfo]
name=Pidgin for RHEL/CentOS $releasever - $basearch - Debug
baseurl=http://rpm.pidgin.im/centos/$releasever/$basearch/debug/
enabled=0
gpgcheck=1
gpgkey=http://rpm.pidgin.im/RPM-GPG-KEY-pidgin

[pidgin-source]
name=Pidgin for RHEL/CentOS $releasever - $basearch - Source
baseurl=http://rpm.pidgin.im/SRPMS/
enabled=0
gpgcheck=1
gpgkey=http://rpm.pidgin.im/RPM-GPG-KEY-pidgin

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