# Controller to agent connectivity failure on UI

**URL:** <https://community.jenkins.io/t/controller-to-agent-connectivity-failure-on-ui/3063>\
**Category:** Using Jenkins\
**Tags:** question\
**Created:** [July 17, 2022, 2:26pm UTC](https://community.jenkins.io/t/controller-to-agent-connectivity-failure-on-ui/3063 "2022-07-17T14:26:09Z")\
**Posts on this page:** 6\
**Page:** 1

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**Author:** ![goutham1992](https://avatars.discourse-cdn.com/v4/letter/g/e56c9b/32.png) [@goutham1992](https://community.jenkins.io/u/goutham1992)\
**Post date:** [July 17, 2022, 2:26pm UTC](https://community.jenkins.io/t/controller-to-agent-connectivity-failure-on-ui/3063/1 "2022-07-17T14:26:09Z")

</div>

I am getting the below error when trying to launch an agent from the Jenkins UI  
Troubleshooting performed,  
Verified the SSH keys on the controller and agent for the user.  
Error message on the UI:

```auto
ERROR: Server rejected the 1 private key(s) for user1 (credentialId:xxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx/method:publickey)
[01/19/17 05:35:15] [SSH] Authentication failed.
hudson.AbortException: Authentication failed.

```

Environement setup : Jenkins Version 2.346.1

# ==== Our Jenkins servers are patched with [root]# ssh -V OpenSSH\_8.8p1 (CentrifyDC build 5.8.1-367) , OpenSSL 3.0.1 14 Dec 2021 [root@xxxx]#

# Note: All SSH keys are verified. The remoting.jar file is temporarily deleted and tried multiple times to relaunch the application.

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**Author:** ![MarkEWaite](https://dub1.discourse-cdn.com/flex013/user_avatar/community.jenkins.io/markewaite/32/20_2.png) [@MarkEWaite](https://community.jenkins.io/u/MarkEWaite)\
**Post date:** [July 17, 2022, 4:15pm UTC](https://community.jenkins.io/t/controller-to-agent-connectivity-failure-on-ui/3063/2 "2022-07-17T16:15:28Z")

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Hi there,

As a reminder, the term “slave” to refer to an agent has been deprecated since 2016. Please refer to [On Jenkins Terminology Updates](https://www.jenkins.io/blog/2020/06/18/terminology-update/) for more details. We request you update your post.

Thanks,  
Mark Waite

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<div class="post-metadata">

**Author:** ![goutham1992](https://avatars.discourse-cdn.com/v4/letter/g/e56c9b/32.png) [@goutham1992](https://community.jenkins.io/u/goutham1992)\
**Post date:** [July 17, 2022, 4:44pm UTC](https://community.jenkins.io/t/controller-to-agent-connectivity-failure-on-ui/3063/3 "2022-07-17T16:44:39Z")

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@MarkEWaite , thanks for the correction, may I know if there is a workaround for the above problem, thanks!

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<div class="post-metadata">

**Author:** ![goutham1992](https://avatars.discourse-cdn.com/v4/letter/g/e56c9b/32.png) [@goutham1992](https://community.jenkins.io/u/goutham1992)\
**Post date:** [July 17, 2022, 5:01pm UTC](https://community.jenkins.io/t/controller-to-agent-connectivity-failure-on-ui/3063/4 "2022-07-17T17:01:45Z")

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I was also able to figure out that the /home/usrname/.ssh that contains the id\_rsa.pub is an “ssh-rsa” that is deprecated with the openssh8.8. Any ideas if creating an ssh-keygen with a different cipher (sha256, sha512) would help the Master and Agent communicate successfully over the Jenkins UI

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<div class="post-metadata">

**Author:** ![MarkEWaite](https://dub1.discourse-cdn.com/flex013/user_avatar/community.jenkins.io/markewaite/32/20_2.png) [@MarkEWaite](https://community.jenkins.io/u/MarkEWaite)\
**Post date:** [July 17, 2022, 5:46pm UTC](https://community.jenkins.io/t/controller-to-agent-connectivity-failure-on-ui/3063/5 "2022-07-17T17:46:03Z")

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Generate a new key. I prefer ED-25519 keys because the text of the key is shorter and easier to copy and paste.

Please also use “Controller” instead of “master”.

The OpenSSH project dropped support for that type of key because they consider that they are not sufficiently secure for current environments.

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<div class="post-metadata">

**Author:** ![goutham1992](https://avatars.discourse-cdn.com/v4/letter/g/e56c9b/32.png) [@goutham1992](https://community.jenkins.io/u/goutham1992)\
**Post date:** [July 17, 2022, 6:31pm UTC](https://community.jenkins.io/t/controller-to-agent-connectivity-failure-on-ui/3063/6 "2022-07-17T18:31:15Z")

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Apologies about the terminology. Noted!!  
Thanks for the suggestion 🙂