GitLab CI: debugging failed jobs

It happens from time to time that a job in a GitLab pipeline fails. Sometimes, however, the error message is too meaningless to be helpful.

Example:

CopyRunning with gitlab-runner 16.7.0 (102c81ba)
  on <host>, system ID: <ID>
Resolving secrets
00:00
Preparing the "shell" executor
00:00
Using Shell (bash) executor...
Preparing environment
00:01
Running on <host>...
Getting source from Git repository
00:00
bash: line 157: /bin/mkdir: Argument list too long
Cleaning up project directory and file based variables
00:00
ERROR: Job failed: exit status 1

For more verbosity your .gitlab-ci.yml can be extended like so:

• List all variables Show archive.org snapshot

  Copy<job>:
    before_script:
      - export
  

  Note

  You can declare an - export either under before_script:, script:, or after_script:, depending on when your job fails.

• Enable debug logging Show archive.org snapshot

  Copy<job>:
    variables:
      CI_DEBUG_TRACE: "true"
  

  Warning

  Debug logging can be a serious security risk. The output contains the content of all variables and other secrets available to the job. The output is uploaded to the GitLab server and visible in job logs.