When attempting to access Webmin via https://[server-ip]:10000, you're encountering connection failures despite having added the iptables rule. The key observations are:

• Port 10000 doesn't appear in iptables -L output when filtering by port number
• A cryptic tcp dpt:webmin entry exists in the firewall rules
• Basic network connectivity to the server is confirmed working

The iptables output shows Webmin is being handled by service name rather than port number. This occurs because Webmin registers itself in /etc/services:

grep webmin /etc/services
webmin        10000/tcp

Your rule addition was technically correct, but let's verify the current effective rules with:

iptables -L -n --line-numbers

Before proceeding further, perform these essential checks:

# Verify Webmin service status
sudo systemctl status webmin

# Check listening ports (should show 10000)
ss -tulnp | grep 10000

# Test local access (bypassing firewall)
curl -vk https://localhost:10000

For production environments, consider these more robust firewall rules:

# Allow established connections
iptables -A INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT

# Specific Webmin rule with logging
iptables -A INPUT -p tcp --dport 10000 -m state --state NEW -j LOG --log-prefix "Webmin Access: "
iptables -A INPUT -p tcp --dport 10000 -m state --state NEW -j ACCEPT

# Alternatively use the service name
iptables -A INPUT -p tcp -m tcp --dport webmin -j ACCEPT

If direct port access remains problematic, consider these approaches:

# SSH tunneling (local port forwarding)
ssh -L 10000:localhost:10000 user@server-ip

# Nginx reverse proxy configuration example
location /webmin/ {
    proxy_pass https://localhost:10000/;
    proxy_redirect https://localhost:10000/ /webmin/;
    proxy_set_header Host $host;
    proxy_set_header X-Real-IP $remote_addr;
    proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
}

Webmin's SSL configuration might cause access problems. Check these key files:

# Verify SSL certificate
sudo cat /etc/webmin/miniserv.pem

# Check SSL configuration
sudo grep ^ssl= /etc/webmin/miniserv.conf

# Temporarily disable SSL for testing (then restart webmin)
sudo perl -pi -e 's/ssl=1/ssl=0/' /etc/webmin/miniserv.conf

After making changes, verify everything is functioning:

# Check firewall rules
sudo iptables-save | grep 10000

# Test external access
telnet your-server-ip 10000

# Examine Webmin logs
tail -f /var/webmin/miniserv.log

Remember to test changes incrementally and document each modification for easy rollback if needed.

---

After installing Webmin on Ubuntu Server, you should verify the service status first:

sudo systemctl status webmin

If the service isn't running, start it with:

sudo systemctl start webmin

The iptables rule you added appears correct, but let's verify the complete firewall configuration:

sudo iptables -L -n --line-numbers

Notice that Webmin uses port 10000 by default, but the service name 'webmin' is also recognized in /etc/services. The equivalent numeric rule would be:

sudo iptables -A INPUT -p tcp --dport 10000 -j ACCEPT

Check if Webmin is actually listening on port 10000:

sudo netstat -tulnp | grep 10000
# Or using ss:
sudo ss -tulnp | grep 10000

If nothing appears, Webmin might not be running or configured to listen on that port.

Examine Webmin's main configuration file:

sudo nano /etc/webmin/miniserv.conf

Key parameters to verify:

port=10000
listen=10000
ssl=1

Try connecting locally first to eliminate network issues:

curl -k https://localhost:10000

If this works, the problem is likely firewall-related. If not, check Webmin logs:

sudo tail -f /var/webmin/miniserv.log

Here's a complete troubleshooting sequence:

# 1. Stop Webmin
sudo systemctl stop webmin

# 2. Reset iptables (temporary)
sudo iptables -F

# 3. Start Webmin
sudo systemctl start webmin

# 4. Add firewall rule
sudo iptables -A INPUT -p tcp --dport 10000 -j ACCEPT

# 5. Verify
sudo iptables -L -n
sudo netstat -tulnp | grep 10000

For Ubuntu systems using UFW:

sudo ufw allow 10000/tcp
sudo ufw enable

For persistent iptables rules on older systems:

sudo apt-get install iptables-persistent
sudo netfilter-persistent save

Webmin defaults to HTTPS. If you get SSL errors, try:

openssl s_client -connect localhost:10000 -showcerts

To temporarily disable SSL for testing, edit /etc/webmin/miniserv.conf and set:

ssl=0

Then restart Webmin.