GitLab-runner - Fixing ssh access

Here is debug process for this situation.

Verify you can logging to remote ssh server manually

Verify you can logging to remote ssh server manually using same local user and same key file than gitlab-runner

sudo su - USER

eval `ssh-agent -s`
ssh-add YOUR_SSH_KEY_FILE
ssh REMOTEU_SER@REMOTE_SERVER

You should solve any issue here before continue.

Launch gitlab-runner log in debug mode

sudo vi /etc/gitlab-runner/config.toml

Add log_level = "debug"

# Sample
concurrent = 1
check_interval = 0
log_level = "debug"
...

Then restart gitlab-runner

sudo gitlab-runner restart

Retry to run buggy job.

If it does not help go to next step.

Launch remote sshd in debug mode

Run SSH daemon on another port as a part of the command (then you don't need to lost your existing session, if already connect thought ssh)

See how-to debug ssh connection.

Then modify gitlab-runner configuration (on gitlab runner host)

sudo vi /etc/gitlab-runner/config.toml

Add port = "2200"

...
[[runners]]
  name = "XXXXX"
  url = "https://XXXXX/"
  token = "XXXXX"
  executor = "ssh"
  [runners.ssh]
    user = "XXXXX"
    host = "XXXXX"
    port = "2200"
    identity_file = "XXXXX"
...

Retry to run buggy job.

On console sshd console you are able to see all gitlab-runner actions and you should be able to understand what is the issue.