• 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)
copied from:
http://serverfault.com/questions/771921/how-to-shrink-home-and-add-more-space-on-centos7
