Question: I am new to unmanaged VPS servers and in addition IPv6. Is it necessary to include 127.0.0.1 AND ::1 for localhost in /etc/hosts files for IPv6 enabled servers, or is ::1 alone enough?

Answer: 
You didn't mention which OS you are using.

On Windows systems, the name resolution of `localhost` is handled by the system and those entries are not needed in the `hosts` file. This is even explicitly mentioned in that very same file:

```
# localhost name resolution is handled within DNS itself.
#   127.0.0.1       localhost
#   ::1             localhost

```
Adding anything to /etc/hosts is not necessary, but really helps, so it will be pretty useful to add both (IPv4 and IPv6) records. After all, it is not expensive in any sense (10 seconds on each won't kill you day), but you'll know this part is done completely.