yum groupinstall "Development Tools"

[vinitRSSB]

[root@client ~]# yum groupinstall "Development Tools"
Loaded plugins: fastestmirror, langpacks
There is no installed groups file.
Maybe run: yum groups mark convert (see man yum)
Loading mirror speeds from cached hostfile
Warning: group Development Tools does not exist.
Maybe run: yum groups mark install (see man yum)
No packages in any requested group available to install or update

[avij]

Try these:
yum clean all
yum --disablerepo=\* --enablerepo=base,updates groupinstall "Development Tools"

If you have EPEL's repo installed it may cause problems for the groupinstall command. The above should work in that situation.