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Debugging with SSH

2 months ago3 min read
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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. There is a possibility that running steps using an interactive login may succeed, but 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 page to learn more.

The build virtual machine (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 the Free plan, or two hours for all other customers.

If your job has parallel steps, CircleCI launches more than one VM to perform them. You will 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 the following in the sections below.

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 both the following in the output:

$ Hi :username! You've successfully authenticated...
$ logged in as :username.

If you do not see output like above, you can try troubleshooting with the following:

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 are 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 have verified that you can authenticate as the correct user, but you are still getting “Permission denied” from CircleCI, you may be offering the wrong credentials to us.

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 public key: /Users/me/.ssh/id_ed25519_github
<...>
debug1: Authentication succeeded (publickey).

This sequence indicates that the key /Users/me/.ssh/id_ed25519_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 public key: ...

Make sure that the key which GitHub accepted (in our example, /Users/me/.ssh/id_ed25519_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_ed25519_github -p 64784 54.224.97.243

When you add the -v flag, you can also run multiple options in verbose mode to get more details, for example:

$ ssh -vv git@github.com

or the maximum of

$ ssh -vvv git@github.com

See also


Help make this document better

This guide, as well as the rest of our docs, are open source and available on GitHub. We welcome your contributions.

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