Dear all, thanks to Urs Beyerle I could already discover and solve the problem.
I created the repositories like this: cat > sl.repo <<EOF > [sl-base] > name=SL 4 base > baseurl=ftp://ftp.scientificlinux.org/linux/scientific/44/$basearch/SL/RPMS/ > enabled=1 > gpgcheck=0 > gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-csieh :///etc/pki/rpm-gpg/RPM-GPG-KEY-dawson :///etc/pki/rpm-gpg/RPM-GPG-KEY-jpolok file:///etc/pki/rpm-gpg/RPM-GPG-KEY-cern > EOF Now $basearch was evaluated and became "", so the value for baseurl was wrong. Consequently yum couldn't update properly. I edited the repositories and now everything works fine. I'm sorry for any inconvenience caused. Kind regards, Xavier Mol. *************************************************************************** The Steinbuch Centre for Computing of Karlsruhe Institute of Technology (the Cooperation of Forschungszentrum Karlsruhe GmbH and Universität Karlsruhe TH) will run its annual GridKa School from September 8th to 12th, 2008. Please find further information at http://www.fzk.de/gks08 . *************************************************************************** **** Abteilung Informationsdienste und Datenmanagement (IDA) Organisationseinheit Steinbuch Centre of Computing (SCC) Forschungszentrum Karlsruhe GmbH Hermann-von-Helmholtz-Platz 1 Leopoldshafen-Eggenstein phone: 07247 82- 3041 e-mail: [EMAIL PROTECTED] Amtsgericht Mannheim, HRB 100302 Vorsitzende des Aufsichtsrates: MinDir'in Bärbel Brumme-Bothe Vorstand (Geschäftsführung): Prof. Dr. Eberhard Umbach (Vorsitzender), Dr. Alexander Kurz (stellv. Vorsitzender), Prof. Dr. Reinhard Maschuw, Dr.-Ing. Peter Fritz, Prof. Dr.-Ing. Detlef Löhe, Prof. Dr. Horst Hippler ****