For Debian-based system execute the following commands:

user@localhost: ~ sudo nano /etc/apt/sources.list

At the end of the file add the line:
deb http://download.webmin.com/download/repository sarge contrib

Add PGP-key.
user@localhost: ~ wget http://www.webmin.com/jcameron-key.asc -nv -O -| sudo sudo apt-key add -

Update local indexes:
user@localhost: ~ sudo apt update

Optionally local packages also can be updated:
user@localhost: ~ sudo apt upgrade


Install webadmin:

user@localhost: ~ sudo apt install webmin

You can check if it is in the list of running processes:

user@localhost: ~ sudo ss -nltp | less

k in the 4^th column for the line “0.0.0.0:10000” and the last should be something like “users:((“miniserv.pl”,pid=24643,fd=5))”
To search in the program ‘less’ enter “/” and type “0.0:10000” and enter. The programm less will highlight the found part of the text

Open in firewall port 10000 for access the server from our subnet – replace <OUR_SUBNET> with our real IP or subnet:

for firewalld execute commands:

user@localhost: ~ sudo firewall-cmd --zone trusted -add-source <OUR_SUBNET>
user@localhost: ~ sudo firewall-cmd --zone trusted --add-port=10000/tcp
user@localhost: ~ sudo firewall-cmd --runtime-to-permanent

For iptables before prohibited rules insert line like this:
(It strongly depends on current settings and before adding review already existing rules using the command: iptables -nvL –line ):

user@localhost: ~ sudo iptables -I INPUT 3 -s <OUR_SUBNET> -p tcp --dport 10000 -j ACCEPT

For nftables into the file /etc/nftables.conf before prohibiting rules insert the line:

ip saddr <OUR_SUBNET> tcp dport 10000 accept

After reload the rules:

user@localhost: ~ sudo nft -f /etc/nftables.conf

Please eter our address into the browser “http://1.2.3.4:1000 – accept the certificate (if there is a domain, register it in the DNS and you can also configure Let’s Encrypt).

Then you can manage your server through the browser