Hello Everybody...

I have just installed trixbox/CentOS. Then need to make some configs, installs, etc.

The problem is, something is wrong with yum/mirrorlist. Tried:

# yum grouplist
# yum update

for both cases, here is the error message that comes out:

... loading fastest mirror login
... determining fastest mirrors
... * trixbox: yum.trixbox.org
... could not retrieve mirror list http://mirrorlist.centos.org/?
... release=5&arch=i386&repo=os error was
... [Errno 4] IOError:
... urlopen error (-3, 'temporary failure in name resolution')
... cannot find a valid baseurl for repo: base

Any hints or suggestion will be mostly appreciated.

Not sure why you think this is a bug

First, can you resolve the url given? Try

dig mirrorlist.centos.org

If that works, try editing you repo file (look in /etc/repos.d, comment out the mirrorlist line(s) and uncomment the base url line(s). See if that works.

If dig didn't work you have a name server issue.

Are you trying to go through a proxy by any chance (if so, configure it in /etc/yum.conf)

Thanks for the inputs. I worked around and clean up things, then now yum is fine again.
Here is what I have done:

# yum clean all
# yum clean metadata
# yum clean dbcache
then fix rpm db
# rpm -vv --initdb
# rm -f /var/lib/rpm/__db*
# rpmdb -vv --rebuilddb

# yum --noplugin update

then deleting the database and rebuilding it.
# rm -f /var/lib/rpm/__db*
# rpmdb -vv --rebuilddb

# yum install yum-utils
# package-cleanup --problems
# package-cleanup --orphans

That's it! Done.