je n'ai pas le sentiment qu'il y ait eu un changement probant.
a tout hasard je copie mon fichier yum.conf. j'ai repris le tutos de yum. je l'avais suivi a la lettrelors de la première install.
"[main]
cachedir=/var/cache/yum
debuglevel=2
logfile=/var/log/yum.log
pkgpolicy=newest
distroverpkg=fedora-release
tolerant=1
exactarch=0
# Added this because some mirrors go down and then retying takes forever.
retries=1
timeout=10
# Basic Repos are in /etc/yum.conf.d/ #
###################
## Fedora Extras ##
###################
[extras]
name=Fedora Extras - $releasever - $basearch
baseurl=
http://fr2.rpmfind.net/linux/fedora/extras/$releasever/$basearch/
http://mirrors.kernel.org/fedora/extras/$releasever/$basearch/
http://mirror.hiwaay.net/redhat/fedora/linux/extras/$releasever/$basearch/
http://www.mirrorservice.org/sites/download.fedora.redhat.com/pub/fedora/linux/extras/$releasever/$basearch/
#
http://download.fedora.redhat.com/pub/fedora/linux/extras/$releasever/$basearch/
gpgcheck=0
gpgkey=
http://download.fedora.redhat.com/pub/fedora/linux/extras/RPM-GPG-KEY-Fedora-Extras
###############
## Livna.org ##
###############
[livna-stable]
name=Livna.org - Fedora Compatible Packages (stable)
baseurl=
http://rpm.livna.org/fedora/$releasever/$basearch/RPMS.stable
http://livna.cat.pdx.edu/fedora/$releasever/$basearch/RPMS.stable
#gpgcheck=1
[livna-unstable]
name=Livna.org - Fedora Compatible Packages (unstable)
baseurl=
http://rpm.livna.org/fedora/$releasever/$basearch/RPMS.unstable
http://livna.cat.pdx.edu/fedora/$releasever/$basearch/RPMS.unstable
#gpgcheck=1
[livna-testing]
name=Livna.org - Fedora Compatible Packages (testing)
baseurl=
http://rpm.livna.org/fedora/$releasever/$basearch/RPMS.testing
http://livna.cat.pdx.edu/fedora/$releasever/$basearch/RPMS.testing
#gpgcheck=1
############
# Jpackage #
############
# JPackage is a GREAT repository for Java Software.
# However, you may have to compile some SRPMs to use it,
# so it's commented out by default. See
# <
http://mirrors.sunsite.dk/jpackage/1.6/generic/non-free/SRPMS>
# For the SRPMs, and <
http://www.jpackage.org/rebuilding.php> for
# the general details.
#
# Note: JPackage IS compatible with the fedora.us repositories.
# You can use JPackage and fedora.us at the same time, without
# any trouble. It's also compatible with the Alternate Repositories,
# for the most part.
[jpackage-generic]
name=JPackage Cross-Platform Packages
baseurl=
http://mirrors.sunsite.dk/jpackage/1.6/generic/free
ftp://jpackage.hmdc.harvard.edu/JPackage/1.6/generic/free
http://sunsite.informatik.rwth-aachen.de/ftp/pub/Linux/jpackage/1.6/generic/free
failovermethod=priority
enabled=0
#gpgcheck=1
[jpackage-fedora]
name=JPackage Fedora Packages
baseurl=
http://mirrors.sunsite.dk/jpackage/1.6/fedora-$releasever/free
ftp://jpackage.hmdc.harvard.edu/JPackage/1.6/fedora-$releasever/free
http://sunsite.informatik.rwth-aachen.de/ftp/pub/Linux/jpackage/1.6/fedora-$releasever/free
failovermethod=priority
enabled=0
#gpgcheck=1
###################
## Miscellaneous ##
###################
# Semi-official Macromedia repository containing the flash-plugin rpm.
[flash]
name=macromedia.mplug.org - Flash Plugin
baseurl=
http://macromedia.mplug.org/apt/fedora/$releasever
http://sluglug.ucsc.edu/macromedia/apt/fedora/$releasever
http://ruslug.rutgers.edu/macromedia/apt/fedora/$releasever
http://macromedia.rediris.es/apt/fedora/$releasever
enabled=0
#gpgcheck=1"
"
j'ai vérifié /etc/yum.repos.d/fedora.repo il est conforme à ce que tu m'as dit.
voila le resultat de mon nouvel essai
"[root@localhost john]# yum install gcc
Repository livna-stable already added, not adding again
Setting up Install Process
Setting up Repo: dries
repomd.xml 100% |=========================| 951 B 00:00
Setting up Repo: dag
repomd.xml 100% |=========================| 951 B 00:00
Setting up Repo: livna-stable
repomd.xml 100% |=========================| 951 B 00:00
Setting up Repo: extras
repomd.xml 100% |=========================| 951 B 00:00
Setting up Repo: updates-released
repomd.xml 100% |=========================| 951 B 00:00
Setting up Repo: livna-unstable
repomd.xml 100% |=========================| 951 B 00:00
Setting up Repo: livna-testing
repomd.xml 100% |=========================| 951 B 00:00
Reading repository metadata in from local files
primary.xml.gz 100% |=========================| 182 kB 00:00
MD Read : ################################################## 717/717
dries : ################################################## 717/717
primary.xml.gz 100% |=========================| 620 kB 00:03
MD Read : ################################################## 1736/1736
dag : ################################################## 1736/1736
livna-stab: ################################################## 146/146
primary.xml.gz 100% |=========================| 244 kB 00:02
MD Read : ################################################## 722/722
extras : ################################################## 722/722
primary.xml.gz 100% |=========================| 276 kB 00:03
MD Read : ################################################## 665/665
updates-re: ################################################## 665/665
livna-unst: ################################################## 38/38
livna-test: ################################################## 39/39
No Match for argument gcc
Nothing to do
"
A++