How to correctly set hostname and domain name?

I am renting a server, running Ubuntu 16.04 at a company, let's name it company.org. Currently, my server is configured like this: - hostname: server737263 - domain name: company.org Here's my FQDN: user@server737263:~ $ hostname --fqdn server737263.company.org This is not surprising. I am also renting a domain name, let's name it domain.org. What I would like to do would be to rename my server as server1.domain.org. This means configuring my hostname as server1 and my domain name as domain.org. **How can I do it correctly?** Indeed, the manpage for hostname is not clear. To me at least: > HOSTNAME(1) > > [...] > > SET NAME > > - When called with one argument or with the --file option, the commands set the host name or the NIS/YP domain name. hostname uses > the sethostname(2) function, while all of the three domainname, > ypdomainname and nisdomainname use setdomainname(2). *Note, that this > is effective only until the next reboot. Edit /etc/hostname for > permanent change.* > > [...] > > THE FQDN > > - *You cannot change the FQDN with hostname or dnsdomainname.* > > [...] So it seems that editing /etc/hostname is not enough? Because if it really changed the hostname, it would have changed the FQDN. There's also a trick I read to change the hostname with the command sysctl kernel.hostname=server1, but nothing says whether this is the correct way or an ugly trick. So: 1. **What is the correct way to set the hostname?** 2. **What is the correct way to set the domain name?**