Debugging with SSH

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This document describes how to access a build container using SSH on CircleCI in the following sections:

• Overview
• Steps
• Debugging: “permission denied (publickey)”

Overview

Often the best way to troubleshoot problems is to SSH into a job and inspect things like log files, running processes, and directory paths. CircleCI gives you the option to access all jobs via SSH. Read our blog post on debugging CI/CD pipelines with SSH.

When you log in with SSH, you are running an interactive login shell. You may be running the command on top of the directory where the command failed the first time, or you may be running the command from the directory one level up from where the command failed (e.g. ~/project/ or ~/). Either way, you will not be initiating a clean run (you may wish to execute pwd or ls to ensure that you are in the correct directory).

Please note that a default CircleCI pipeline executes steps in a non-interactive shell and hence, there is the possibility that running steps using an interactive login may succeed, while failing in non-interactive mode.

Steps

1. Ensure that you have added an SSH key to your GitHub or Bitbucket account.

2. To start a job with SSH enabled, select the ‘Rerun job with SSH’ option from the ‘Rerun Workflow’ dropdown menu.

   Note: The Rerun job with SSH feature is intended for debugging purposes. These jobs will be created inside of the same pipeline as the original job.

3. To see the connection details, expand the ‘Enable SSH’ section in the job output where you will see the SSH command needed to connect.

   The details are displayed again in the ‘Wait for SSH’ section at the end of the job.

4. SSH to the running job (using the same SSH key that you use for GitHub or Bitbucket) to perform whatever troubleshooting you need to.

If you are using the Windows executor you will need to pass in the shell you want to use when using SSH. For example, To run powershell in your build you would run: ssh -p <remote_ip> -- powershell.exe. Consider reading the Hello World on Windows document to learn more.

The build VM will remain available for an SSH connection for 10 minutes after the build finishes running and then automatically shut down (or you can cancel it). After you SSH into the build, the connection will remain open for one hour for customers on a free plan or two hours for all other customers.

Note: If your job has parallel steps, CircleCI launches more than one VM to perform them. Thus, you’ll see more than one ‘Enable SSH’ and ‘Wait for SSH’ section in the build output.

Debugging: “permission denied (publickey)”

If you run into permission troubles trying to SSH to your job, try these things:

Ensure authentication with GitHub/Bitbucket

A single command can be used to test that your keys are set up as expected. For GitHub run:

ssh git@github.com

or for Bitbucket run:

ssh -Tv git@bitbucket.org

and you should see:

$ Hi :username! You've successfully authenticated...

for GitHub or for Bitbucket:

$ logged in as :username.

If you don’t see output like that, you need to start by troubleshooting your SSH keys with GitHub/ troubleshooting your SSH keys with Bitbucket.

Ensure authenticating as the correct user

If you have multiple accounts, double-check that you are authenticated as the right one!

In order to SSH into a CircleCI build, the username must be one which has access to the project being built!

If you’re authenticating as the wrong user, you can probably resolve this by offering a different SSH key with ssh -i. See the next section if you need a hand figuring out which key is being offered.

Ensure the correct key is offered to CircleCI

If you’ve verified that you can authenticate as the correct user, but you’re still getting “Permission denied” from CircleCI, you may be offering the wrong credentials to us. (This can happen for several reasons, depending on your SSH configuration.)

Figure out which key is being offered to GitHub that authenticates you, by running:

$ ssh -v git@github.com

# Or

$ ssh -v git@bitbucket.com

In the output, look for a sequence like this:

debug1: Offering RSA public key: /Users/me/.ssh/id_rsa_github
<...>
debug1: Authentication succeeded (publickey).

This sequence indicates that the key /Users/me/.ssh/id_rsa_github is the one which GitHub accepted.

Next, run the SSH command for your CircleCI build, but add the -v flag. In the output, look for one or more lines like this:

debug1: Offering RSA public key: ...

Make sure that the key which GitHub accepted (in our example, /Users/me/.ssh/id_rsa_github) was also offered to CircleCI.

If it was not offered, you can specify it via the -i command-line argument to SSH. For example:

$ ssh -i /Users/me/.ssh/id_rsa_github -p 64784 54.224.97.243

See also

GitHub and Bitbucket Integration

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