how f ix this error

2018-09-28 02:26:59 547 (ERROR): ********************* ERROR *********************
2018-09-28 02:26:59 548 (ERROR):
2018-09-28 02:26:59 549 (ERROR): Your hostname (centos-s-1vcpu-2gb-lon1-01) is invalid, and must be
2018-09-28 02:26:59 550 (ERROR): set to a fully qualified domain name before installing cPanel.
2018-09-28 02:26:59 551 (ERROR):
2018-09-28 02:26:59 552 (ERROR): A fully qualified domain name must contain two dots, and consists of two parts: the hostname and the domain name.
2018-09-28 02:26:59 553 (ERROR): You can update your hostname by running hostname your-hostname.example.com, then re-running the installer.
2018-09-28 02:26:59 555 (ERROR): ********************* ERROR *********************
2018-09-28 02:26:59 556 (FATAL): Exiting…
Removing /root/installer.lock.