cd /etc/yum.repos.d
wget http://people.centos.org/tru/devtools/devtools.repo
yum --enablerepo=testing-devtools-6 install devtoolset-1.0/opt/centos/devtoolset-1.0/root/usr/bin/g++
As others have pointed out, XFS filesystem cannot be shrunk.
So your best bet is to backup /home, remove and recreate its volume in a smaller size and give the rest to your /root volume just as Koen van der Rijt outlined in his post.
• backup the contents of /home
> tar -czvf /root/home.tgz -C /home .
• test the backup
> tar -tvf /root/home.tgz
• unmount home
> umount /dev/mapper/centos-home
• remove the home logical volume
> lvremove /dev/mapper/centos-home
• recreate a new 400GB logical volume for /home, format and mount it
> lvcreate -L 400GB -n home centos
> mkfs.xfs /dev/centos/home
> mount /dev/mapper/centos-home
• extend your /root volume with ALL of the remaining space and resize (-r) the file system while doing so
> lvextend -r -l +100%FREE /dev/mapper/centos-root
• restore your backup
> tar -xzvf /root/home.tgz -C /home
• check /etc/fstab for any mapping of /home volume. IF it is using UUID you should update the UUID portion. (Since we created a new volume, UUID has changed)
That's it.
Hope this helps.