Ubuntu – SSH refusing connection after changing default port

serverssh

currently I'm handling 2 server (A and B).
In server A I installed Ubuntu 12.10. I changed the SSH port into 1198 and it works fine. In server B it has been installed with Ubuntu 11.04. I tried to change the port number into 1198 as well but it refused the connection when I tried to connect again using Putty.

I change the SSH configuration on /etc/ssh/sshd_config and I did restart the SSH using sudo service ssh restart. I was thinking its because of firewall allowed port but the firewall shows inactive when I run sudo ufw status.

Any idea why this can happened?

Best Answer

I wanted to share my experience for anyone else that may run into this.

After changing the port and restarting the SSH service as you also tried, I was still not able to connect on the new port I specified. When I ran sudo netstat -lntp | grep ssh it showed that my SSH service was still listening on port 22, despite supposedly successfully restarting the service.

Only after rebooting the machine and re-running netstat I saw my service was finally listening on the specified port.

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Ubuntu – SSH connection refused when connecting remotly

If I am reading your question right, it sounds like you are using putty on windows, to connect to ubuntu. It also sounds like you are giving putty the IP 127.0.0.1. If that is the case, you are telling putty to connect to your windows computer. To find the IP on ubuntu, you could run ip addr show (on the ubuntu computer), then use the IP address for the interface you are using for internet (en0, wlan0, etc) with putty.

Ubuntu – SSH resets to default port on reboot

ssh may be "socket activated" by systemd depending on configuration, which means that initially it is systemd that sets up the listening port, and sshd is only started when a client first connects. This is to speed up startup time: service daemons are only started on demand.

However this means that you must also configure systemd to the matching port. You'll find the system configuration in /lib/systemd/system/ssh.socket which lists ListenStream=22. To override this, create a file /etc/systemd/system/ssh.socket.d/port.conf (creating the directory ssh.socket.d if needed) that contains:

[Socket]
ListenStream=
ListenStream=54747

Change the number to the port desired. The first blank entry erases the previous default, and the subsequent entry adds the new one. This overrides the default shipped in /lib/systemd/system/ssh.socket and must be done in addition to changing /etc/ssh/sshd_config.

Then run sudo systemctl daemon-reload to tell systemd about your changes, and sudo systemctl reload ssh if your ssh daemon was previously running.

Best Answer

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