Cannot restart SSH daemon after changing sshd_config to port 2222

Question

I have been looking around and couldn't find a solution to the issue I am having. I am running Ubuntu 16.04 LTS, and I followed instructions on the Ubuntu page for changing the SSH port to 2222 by updating the sshd_config file.

# What ports, IPs and protocols we listen for
Port 2222

When I execute the command sudo systemctl restart sshd.service, however, I only get the following error:

Job for ssh.service failed because the control process exited with error code. See "systemctl status ssh.service" and "journalctl -xe" for details.

I then executed the command systemctl status ssh.service and got

● ssh.service - OpenBSD Secure Shell server
   Loaded: loaded (/lib/systemd/system/ssh.service; enabled; vendor preset: enabled)
   Active: failed (Result: exit-code) since Wed 2016-09-07 23:24:04 EDT; 1min 28s ago
  Process: 16813 ExecStart=/usr/sbin/sshd -D $SSHD_OPTS (code=exited, status=255)
 Main PID: 16813 (code=exited, status=255)

Sep 07 23:24:04 sys-0 systemd[1]: Starting OpenBSD Secure Shell server...
Sep 07 23:24:04 sys-0 systemd[1]: ssh.service: Main process exited, code=exited, status=255/n/a
Sep 07 23:24:04 sys-0 systemd[1]: Failed to start OpenBSD Secure Shell server.
Sep 07 23:24:04 sys-0 systemd[1]: ssh.service: Unit entered failed state.
Sep 07 23:24:04 sys-0 systemd[1]: ssh.service: Failed with result 'exit-code'.

What does the error mean, and how can I address it?

Solution 1

As @techraf said, most likely you made a simple mistake in your /etc/ssh/sshd_config. Try sshd test mode:

$ sudo sshd -t
/etc/ssh/sshd_config: line 1: Bad configuration option: sds

From man page:

• -t Test mode. Only check the validity of the configuration file and sanity of the keys. This is useful for updating sshd reliably as configuration options may change.
• -T Extended test mode. Check the validity of the configuration file, output the effective configuration to stdout and then exit. Optionally, Match rules may be applied by specifying the connection parameters using one or more -C options.

Solution 2

Are you running on a system that utilizes SELinux? It could be that this is denying the port bind; try adding in a new rule.

semanage port -a -t ssh_port_t -p tcp 2222

Comments

[techraf]

Most likely you made a simple mistake in your sshd_config. What if you put back the original one?

[Paul]

sudo sshd -vvvf /etc/ssh/sshd_config should give you clue as to what is wrong

[FullStack]

When I put back the original one, it works as usual. However, port 2222 worked for me today doing the exact same thing I did last night. Very odd.

[FullStack]

@techraf I deleted the other one. I'm never sure which SE is better for this type of question

[Pablo A]

@Paul on openssh-server 1:7.4p1-10+deb9u2 on Debian 9 I get unknown option -- v.

[FullStack]

no, I am not running on SELinux, but somehow this morning doing the same things worked. Thanks so much for your input

[Sayali]

Still the same error, nothing has changed

[HugoWeb]

Thanks this helped me!

[KansaiRobot]

this helped me a lot!

[HorstKevin]

How is this related to the question?