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Vagrant ssh key authentication failure – Let’s fix it!

Struggling with Vagrant ssh key authentication failure? We can help you fix it.

Vagrant creates and manages a virtual machine environment within minutes. But we encounter many problems like ssh key authentication failure due to incorrect configuration while using vagrant.

At Bobcares, we get requests on Vagrant errors from our customers, as a part of our Server Management Services.

Today, let’s see how our Support Engineers fix the error for our customers.

Why vagrant ssh key authentication failure?

The main reason for the failure of authentication is wrong configurations in the vagrant file. Recently one of our customers approached us saying that when he runs ‘vagrant up’ command, he is getting an  authentication error message as shown below:

default: Warning: Authentication failure. Retrying...

We checked and found some wrong configuration settings in the vagrant file. So we made the following changes in the file. The customer mentioned that he wants to ssh as an Ubuntu user. So,firstly we commented  the below line in the vagrant file for confirming whether we are able to ssh as a vagrant user.config.ssh.username = "ubuntu"

Secondly, we ran the command vagrant ssh-config in order to find IdentityFile.

Vagrant ssh key authentication failure

The important information in this file is HostName, User, Port, and IdentityFile. These parameters can be used as connection information for the custom SSH connection. After that  we generated the key using the command below:

ssh-keygen -y -f < Here given the path we got from IdentityFile >

Then we tried to ssh using vagrant ssh command and was successfully authenticated as the vagrant user. But our customer mentioned that he is using Ubuntu OS, and he was facing the failure when trying to ssh as Ubuntu user.

So our Support Engineers switched as Ubuntu user and added the key we generated to  ~/.ssh/authorized_keys. Then exited from VM using the exit command. Then we tried ssh as an ubuntu user. For that, we  removed the comment on  line config.ssh.username = “ubuntu” in Vagrant file that we commented before for the checking purpose.

And reloaded vagrant using the command:

vagrant reload

And ran vagrant ssh as the ubuntu user.

Finally, we successfully authenticated as an ubuntu user.


[Having trouble in solving vagrant errors? Come to us, we’ll help you.]



In conclusion, vagrant ssh key authentication failure occurs mainly due to wrong configurations in the vagrant file. Today, we discussed in detail on this and saw how our Support Engineers fix this authentication failure error.


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