How to create an uninterrupted hosting of internal company sites?

Question

Network administration

What do you need and what exactly to google to deploy your uninterrupted hosting for internal needs?
For example, there is an internal portal. Its host receives updates periodically and requires a reboot. What and how to configure so that at this moment the site remains working (I understand that in this case there should be at least 2 hosts updated in turn, but specific solutions are needed)?
ps If I google "how to set up hosting" or "how to create hosting", then I am offered to buy vds, panels, etc.
pps No, we will not go to a ready-made external hosting.

Answer 1

very rude: there is a machine, two virtual machines and a dns server are installed on it, the whole zoo is on virtual machines (nginx, php, mysql), replication between databases, synchronization between folders, and do not forget about backups

Answer 2

Firstly, you need to rewrite the portal so that it supports geo-distribution and at least two databases at the same time.
Then you need to raise independent and geo-spaced servers
. Then set up a tricky DNS that would switch everything between them
. still works

Answer 3

ps If I google "how to set up hosting" or "how to create hosting", then I am offered to buy vds, panels, etc.

That's right. If you do not want to suffer with configs, then install the control panel. You can also on your server.