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2025-09-03 14:11:38 admin: added original dokuwiki page| /dev/null .. ssh.md | |
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| + | # SSH |
| + | |
| + | ## Port change |
| + | |
| + | In version from Ubuntu newer than 22.04, the SSHD is controlled by |
| + | Systemd and no longer with the older process way. To change the port, it |
| + | needs to be done by changing the config from Systemd |
| + | |
| + | A ssh.socket socket is activated in Systemd to listen to the port, when |
| + | triggered, it will start the ssh.service (which does not need to be |
| + | started beforehand, it save memory if no ssh connection is done) |
| + | |
| + | It is done that way on the OVH VPS: |
| + | |
| + | 1. Changing the port in a `listen.conf` file |
| + | 1. sudo nano /etc/systemd/system/ssh.socket.d directory (do not |
| + | change in /lib/systemd...) |
| + | |
| + | ``` yaml |
| + | [Socket] |
| + | # Uncomment the following line to turn of listening on port 22. |
| + | ListenStream= |
| + | ListenStream=0.0.0.0:xxxxx |
| + | ``` |
| + | |
| + | The empty `ListenStream` is necessary to prevent default port |
| + | activation. the 0.0.0.0 is for IP v4, use [::] for IP v6. Ubuntu |
| + | default instruction for port to be IP v6 is not specified. |
| + | |
| + | Use `systemctl show ssh.socket` to see the config of the socket |
| + | |
| + | 1. Restart the services |
| + | 1. `sudo systemctl daemon-reload` |
| + | 2. `sudo systemctl restart ssh.socket` |
| + | |
| + | It seems, it should be possible to only do the change with |
| + | |
| + | 1. `sudo systemctl edit ssh.socket` |
| + | |
| + | then do the reload/restart |
| + | |
| + | Then, when calling ssh, do not forget to add -p <port> (see Bitwarden |
| + | for port) |
| + | |
| + | To check ssh access, use Systemd login: |
| + | |
| + | ``` bash |
| + | journalctl -u ssh -n 50 -e --no-pager |
| + | ``` |
| + | |
| + | In Systemd, 'ssh' without other information is defaulted to service. |
| + | So ssh.socket needs to be explicit to see the socket instead of the |
| + | service. |
| + | |
| + | That Systemd logging is used by fail2ban to function. |
| + | |
| + | [One info page](https://lafibre.info/serveur-linux/changer-le-port-de-ssh-ubuntu-24-04/) |