How can I see a ssh error log?

Hi. Thank you all guys for creating and sharing these great apps.
I'm using Gitlab 8.6.4 of sameersbn/docker-gitlab now.

I was looking up /var/log/gitlab/gitlab-shell/gitlab-shell.log but there was no error log when our client failed to connect ssh because of an invalid id_rsa file.

I found log_level setting in config.yml but couldn't find any document of this parameter.

I saw docs like these.

• http://doc.gitlab.com/omnibus/settings/logs.html
• http://doc.gitlab.com/ce/logs/logs.html
• https://gitlab.com/gitlab-org/gitlab-shell

What value of log_level will show the errors in gitlab-shell.log and how will I be able to apply it on my running gitlab?

I hope you'll be able to provide some information.

Thank you.