Debugging Jobs Over SSH
Basics > Debugging Jobs Over SSH
This document describes how to access a build container using SSH on CircleCI 2.0 in the following sections:
- Debugging: “Permission denied (publickey)”
Often the best way to troubleshoot problems is to SSH into a build container and inspect things like log files, running processes, and directory paths. CircleCI 2.0 gives you the option to access all jobs via SSH.
When you log in with SSH, you are running an interactive login shell. You are also likely to be running the command on top of the directory where the command failed the first time, so you are not starting a clean run. In contrast, CircelCI uses a non-interactive shell for running commands by default. Hence, steps run in interactive mode may succeed, while failing in non-interactive mode.
To start a build with SSH enabled, select the ‘Rebuild with SSH’ option from the ‘Rebuild’ dropdown menu:
To see the connection details, expand the ‘Enable SSH’ section in the build 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.
SSH to the running build (using the same SSH key that you use for GitHub or Bitbucket) to perform whatever troubleshooting you need to.
The build VM will remain available for 30 minutes after the build finishes running and then automatically shut down. (Or you can cancel it.)
Note: If your build 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 build, 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 email@example.com
or for Bitbucket run:
ssh -Tv firstname.lastname@example.org
and you should see:
Hi :username! You've successfully authenticated...
for GitHub or for Bitbucket:
logged in as :username.
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 email@example.com # or $ ssh -v firstname.lastname@example.org
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
argument to SSH. For example:
$ ssh -i /Users/me/.ssh/id_rsa_github -p 64784 email@example.com