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I'm trying to connect with a specific key on a server but for some reason I cannot connect with my private key if the public key exists next to it. Both clients and servers are Ubuntu 16.04.

The current situation: I have my ssh keys in my .ssh folder:

samk@local:~$ ls -ld .ssh
drwx------ 2 samk samk 4096 Oct 29 11:36 .ssh
samk@local:~$ ls -l .ssh/jenkins-slave*
-rw------- 1 samk samk 1679 Oct 24 13:23 .ssh/jenkins-slave_rsa
-rw------- 1 samk samk  429 Oct 24 12:09 .ssh/jenkins-slave_rsa.pub

The problem is I cannot connect using my ssh private key:

samk@local:~$ /usr/bin/ssh -i ~/.ssh/jenkins-slave_rsa ubuntu@jenkins-slave-01
Permission denied (publickey).

If I rename the public key to something else, I can connect:

samk@local:~$ mv .ssh/jenkins-slave_rsa.pub .ssh/jenkins-slave_other
samk@local:~$ /usr/bin/ssh -i  ~/.ssh/jenkins-slave_rsa  ubuntu@jenkins-slave-01

Welcome to Ubuntu 16.04.5 LTS (GNU/Linux 4.4.0-137-generic x86_64)
Last login: Mon Oct 29 10:25:32 2018 from 192.168.0.88

ubuntu@jenkins-slave-01:~$

If I rename back the public key, I cannot connect anymore.

What is happening here?

  • 2
    You appear to be going to 2 different hosts, jenkins-slave-01 in the first one (failed one), and jenkins-slave in the second one (good one). Also, you are invoking /usr/bin/ssh in the first one, and just ssh in the second one. Make sure you are running /usr/bin/ssh in both, and going to the same host in both. Also, if you want to ssh into a server without using a password, just the public key, the public key needs to be added into the remote users authorized_keys file. The best way to do that is to run ssh-copy-id. Hope this helps. – Lewis M Oct 29 '18 at 12:32
  • Hey Lewis, thank you for your response, that was just a typo, sorry about that. This is indeed the same host. I will correct my post. – SamK Oct 29 '18 at 13:30
  • The public key hosted locally happened to be the wrong one. Even if the file was wrong, I don't understand why ssh would refuse the connection. – SamK Oct 29 '18 at 14:42
  • try chmod 644 .ssh/jenkins-slave_rsa.pub – Alvin Liang Oct 29 '18 at 21:28
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It happened that the public key (.ssh/jenkins-slave_rsa.pub) was not matching with the private key (.ssh/jenkins-slave_rsa.pub).

I discovered this while following the steps in this answer: https://serverfault.com/a/426429/30128

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