Add info on CI job traces for admins

doc/administration/index.md

@@ -111,6 +111,7 @@ server with IMAP authentication on Ubuntu, to be used with Reply by email.
 - [Enable/disable GitLab CI/CD](../ci/enable_or_disable_ci.md#site-wide-admin-setting): Enable or disable GitLab CI/CD for your instance.
 - [GitLab CI/CD admin settings](../user/admin_area/settings/continuous_integration.md): Define max artifacts size and expiration time.
 - [Job artifacts](job_artifacts.md): Enable, disable, and configure job artifacts (a set of files and directories which are outputted by a job when it completes successfully).
+- [Job traces](job_traces.md): Information about the job traces (logs).
 - [Artifacts size and expiration](../user/admin_area/settings/continuous_integration.md#maximum-artifacts-size): Define maximum artifacts limits and expiration date.
 - [Register Shared and specific Runners](../ci/runners/README.md#registering-a-shared-runner): Learn how to register and configure Shared and specific Runners to your own instance.
 - [Shared Runners pipelines quota](../user/admin_area/settings/continuous_integration.md#shared-runners-pipeline-minutes-quota): Limit the usage of pipeline minutes for Shared Runners.

doc/administration/job_traces.md

+# Job traces (logs)
+
+By default, all job traces (logs) are saved to `/var/opt/gitlab/gitlab-ci/builds`
+and `/home/git/gitlab/builds` for Omnibus packages and installations from source
+respectively. The job logs are organized by year and month (for example, `2017_03`),
+and then by project ID.
+
+There isn't a way to automatically expire old job logs, but it's safe to remove
+them if they're taking up too much space. If you remove the logs manually, the
+job output in the UI will be empty.
+
+## Changing the job traces location
+
+To change the location where the job logs will be stored, follow the steps below.
+
+**In Omnibus installations:**
+
+1.  Edit `/etc/gitlab/gitlab.rb` and add or amend the following line:
+
+    ```
+    gitlab_ci['builds_directory'] = '/mnt/to/gitlab-ci/builds'
+    ```
+
+1. Save the file and [reconfigure GitLab][] for the changes to take effect.
+
+---
+
+**In installations from source:**
+
+1. Edit `/home/git/gitlab/config/gitlab.yml` and add or amend the following lines:
+
+    ```yaml
+    gitlab_ci:
+      # The location where build traces are stored (default: builds/).
+      # Relative paths are relative to Rails.root.
+      builds_path: path/to/builds/
+    ```
+
+1. Save the file and [restart GitLab][] for the changes to take effect.
+
+[reconfigure gitlab]: restart_gitlab.md#omnibus-gitlab-reconfigure "How to reconfigure Omnibus GitLab"
+[restart gitlab]: restart_gitlab.md#installations-from-source "How to restart GitLab"