I've got the CoreOS running and I would like to remove the ability to login using passwords to the sshd. I went through the docs of the CoreOS in here, but I am quite new to the systemd. I went through the man page, but I am a bit lost on it. I know I have to create a dropin file inside /etc/system.d/system/, but I have no idea, in which section of the file, should I put the PasswordAuthentication no option. Since I work remotely, I don't want to screw up and not be able to login again...

I would be grateful for some guidance.


After having a chat on #coreos on freenode, I have learned the simples thing of all.

/etc is not read only, but sshd_config is a symlink to a file on /usr which is. I just had to remove the symlink and create the file by hand... eh.


You have to edit the file /etc/ssh/sshd_config, you will find PasswordAuthentication there. Then restart the SSHD with systemctl restart sshd

  • Thanks @Stone but this is CoreOS and the file is on a read only partition, that's why I have to do this using a dropin file. – Krystian Jan 10 '18 at 9:31
  • Oh sorry, I was misread CoreOS to CentOS... :( – Stone Jan 10 '18 at 9:34
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    The configuration of /etc/ssh/sshd_config is in the very first configuration block of your linked instructions. Just add the line. – Gerald Schneider Jan 10 '18 at 9:35
  • @GeraldSchneider I'm sorry I don't understand. Sorry for my ignorance, but where do I add the line? – Krystian Jan 10 '18 at 9:40
  • @GeraldSchneider if your advice was to modify the /etc/ssh/sshd_config, then as stated before, this file is on a read only partition, and according to the docs, the only way to configure sshd after first boot is by using the dropin files: coreos.com/os/docs/latest/customizing-sshd.html What I miss is info on a section which I could use to pass the PasswordAuthentication option – Krystian Jan 11 '18 at 7:32

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