Unable to SSH login at all after disabling root login via SSH

[centipedesquad]

I was following the instructions here to disable root password access. I did this:
/boot/dietpi/func/dietpi-set_software disable_ssh_password_logins root dietpi-software reinstall 104 # reinstall Dropbear

However, since I reinstalled Dropbear and then restarted my RPi 5, I am unable to ssh into my user (not root user) using the password either. I am getting an ssh: connect to host xxx: Operation timed out error when trying to log in to either root or the other user.

Since by default, I don't have the location /etc/ssh/sshd_config.d/zz-disable-root-login.conf and I am getting this error:
bash: /etc/ssh/sshd_config.d/zz-disable-root-login.conf: No such file or directory
(because I assume it is specific to openssh and not Dropbear)
I hadn't performed this step.

Any suggestions as to what might be the problem, and what could I do to resolve it?

Unfortunately, just before this I have also installed and run fail2ban, so I am not sure which of the changes is causing the error.

Apologies. I am new to all this, so I might have made a rather elementary error.

Thanks!

[Joulinar]

Easiest way would be to get local consol access by connecting screen and keyboard.

[Joulinar]

are you able to login locally now? If yes, you can run following to revert the settings

/boot/dietpi/func/dietpi-set_software disable_ssh_password_logins 0

[MichaIng]

If is still does not work, please check

journalctl -u dropbear

It is not needed to reinstall Dropbear after the change, restarting its service is sufficient. The config is at /etc/default/dropbear. Can you run the command again and paste the content of this config file?

/boot/dietpi/func/dietpi-set_software disable_ssh_password_logins root
cat /etc/default/dropbear

... actually something to add to our docs: https://dietpi.com/docs/software/ssh/

[centipedesquad]

Thanks!
Not yet, I hadn't realised that a USB-C monitor can't be connected to RBP while simultaneously powering it. So I have ordered a micro-HDMI to HDMI adapter and will try connecting it to my TV. Will post as soon as I am able to do so.

[MichaIng]

A UART adapter for serial console access would be an alternative.

Also, if you have another Linux system where you can attack the drive/SD card to, you could manually check and in case edit the Dropbear config from there.

[centipedesquad]

If is still does not work, please check

journalctl -u dropbear

It is not needed to reinstall Dropbear after the change, restarting its service is sufficient. The config is at /etc/default/dropbear. Can you run the command again and paste the content of this config file?

/boot/dietpi/func/dietpi-set_software disable_ssh_password_logins root
cat /etc/default/dropbear

... actually something to add to our docs: https://dietpi.com/docs/software/ssh/
Here is what has happened:

1. I ran /boot/dietpi/func/dietpi-set_software disable_ssh_password_logins 0 after connecting the RPi to a monitor and keyboard. Then after restarting the Pi, then I was able to login using ssh to any user.

2. Then, I ran /boot/dietpi/func/dietpi-set_software disable_ssh_password_logins root and then restarted the Pi. I was unable to login through ssh again. After that, I was able to login through ssh the moment I connected an external monitor, but without changing anything locally. It happened rather accidentally, I ran the ssh command turned to connect the external monitor just to see what it was displaying. When I turned back again and put in the password it logged in. Now it is true that one might say that I might have input the password incorrectly but since I was trying to eliminate any such possibility I was pasting my password into the iterm terminal anyways :)
   Since then I have been able to ssh login into all users except the root as I would expect it to work. Here are the outputs in any case

• journalctl -u dropbear returns:

xxxxxx@DietPi:~$ sudo journalctl -u dropbear
Sep 06 20:48:58 DietPi systemd[1]: Started dropbear.service - Lightweight SSH server.
Sep 06 20:48:58 DietPi dropbear[527]: [527] Sep 06 20:48:58 Failed loading /etc/dropbear/dropbear_dss_host_key
Sep 06 20:48:58 DietPi dropbear[527]: [527] Sep 06 20:48:58 Not backgrounding
Sep 06 20:48:59 DietPi dropbear[578]: [578] Sep 06 20:48:59 Child connection from 192.168.1.193:61455
Sep 06 20:48:59 DietPi dropbear[578]: [578] Sep 06 20:48:59 Failed loading /etc/dropbear/dropbear_dss_host_key
Sep 06 20:49:43 DietPi dropbear[578]: [578] Sep 06 20:49:43 Exit before auth from <192.168.1.193:61455>: (user 'root', 3 fails): Exited normally
Sep 06 20:49:56 DietPi dropbear[1337]: [1337] Sep 06 20:49:56 Child connection from 192.168.1.193:61466
Sep 06 20:49:56 DietPi dropbear[1337]: [1337] Sep 06 20:49:56 Failed loading /etc/dropbear/dropbear_dss_host_key
Sep 06 20:50:04 DietPi dropbear[1337]: [1337] Sep 06 20:50:04 Password auth succeeded for 'xxxxxx' from 192.168.1.193:61466
Sep 06 20:50:39 DietPi sudo[1648]: xxxxxx : TTY=pts/0 ; PWD=/home/xxxxxx ; USER=root ; COMMAND=/usr/bin/apt upgrade
Sep 06 20:50:39 DietPi sudo[1648]: pam_unix(sudo:session): session opened for user root(uid=0) by xxxxxx(uid=1001)

• and the contents of the config files arecat /etc/default/dropbear:
  

These don't show any issue as far as I understand. I haven't tried it, but if you would like me to reproduce the issue, I could try /boot/dietpi/func/dietpi-set_software disable_ssh_password_logins 0 and /boot/dietpi/func/dietpi-set_software disable_ssh_password_logins root again. Otherwise, I will close the issue in a few days just to be sure that things continue to work. Thanks again for your assistance.