After reinstalling your OS using the CentOS 7 KVM Template within SolusVM, you may end up with a real small / partition.
In order to resolve this and get your full disk space, please run this simple command:
resize2fs /dev/vda1
Once you run that, run df -h to confirm the disk space is correct.
If you continue to have issues, please contact support: https://hostodo.com/portal/submitticket.php
