Questions[webmin](ubuntu)

I searched and found similar questions but none were specific enough or solved my issue. An example would be this question Starting remote script/terminal based programs through ssh gives error (Error opening terminal: unknown.) which I am not using ssh so -t will not help.

Running webmin, has been fine for months and now I get this error.

Basically when I type nano or vi into terminal, I get the error "Error opening terminal: unknown."

[user@host ~]# nano
Error opening terminal: unknown.
[user@host ~]# lsb_release -a
No LSB modules are available.
Distributor ID: Ubuntu
Description: Ubuntu 16.04.3 LTS
Release: 16.04
Codename: xenial
[user@host ~]# nano
Error opening terminal: unknown.

[user@host ~]# 

How do I fix "Error opening terminal: unknown." on Ubuntu 16.04.3 LTS running webmin?

New information:

1. When I try running vi or nano directly on the server instead of using webmin or ssh to remote in, it works. Could this just be a problem with webmin?
2. When I examine the environment variables it say's TERM=linux which is consistent with my other server which is running all the same software.

Is there a way to disable the GUI in the desktop version of Ubuntu 18.04. so save on power consumption during idle states?

Since I won't have a monitor hooked up to the machine anyway, I'd rather manage Ubuntu through an SSH connection or Webmin.

How do I install webmin on Ubuntu 12.04?

Note: I am using the desktop edition, not Ubuntu Server.

I have 10.04 32bit dedicated server. just installed 10min ago.

I need to create ftp and ssh accounts.

I used to use cpanel in my old server. Are there any free panel? or how can I create ftp accounts ?

I have my own server application in C, I bind my server on localhost address 127.0.0.1 and let it listen in first case on port 10000 and in second case on port 20000. When I run command I lsof | grep IP in last column is: in the first case: localhost:webmin (LISTEN)
and, in the second case: localhost:20000 (LISTEN)

So instead of port 10000 there is webmin. What does it mean? I found this. It says that Webmin is a web-based interface for system administration for Unix but that isn't enough clear explanation. So what webmin exactly mean?