Add geo log, registry log, nginx logs to doc

doc/administration/logs.md

@@ -635,6 +635,43 @@ Each line contains a JSON line that can be ingested by Elasticsearch. For exampl
 }
 ```
 
+## `geo.log`
+
+> Introduced in 9.5.
+
+Geo stores structured log messages in a `geo.log` file. For Omnibus installations, this file is at `/var/log/gitlab/gitlab-rails/geo.log`.
+
+This file contains information about when Geo attempts to sync repositories and files. Each line in the file contains a separate JSON entry that can be ingested into. For example, Elasticsearch or Splunk.
+
+For example:
+
+```json
+{"severity":"INFO","time":"2017-08-06T05:40:16.104Z","message":"Repository update","project_id":1,"source":"repository","resync_repository":true,"resync_wiki":true,"class":"Gitlab::Geo::LogCursor::Daemon","cursor_delay_s":0.038}
+```
+
+This message shows that Geo detected that a repository update was needed for project `1`.
+
+## Registry Logs
+
+For Omnibus installations, Container Registry logs reside in `/var/log/gitlab/registry/current`.
+
+## NGINX Logs
+
+For Omnibus installations, NGINX logs reside in:
+
+- `/var/log/gitlab/nginx/gitlab_access.log` contains a log of requests made to GitLab.
+- `/var/log/gitlab/nginx/gitlab_error.log` contains a log of NGINX errors for GitLab.
+- `/var/log/gitlab/nginx/gitlab_pages_access.log` contains a log of requests made to Pages static sites.
+- `/var/log/gitlab/nginx/gitlab_pages_error.log` contains a log of NGINX errors for Pages static sites.
+- `/var/log/gitlab/nginx/gitlab_registry_access.log` contains a log of requests made to the Container Registry.
+- `/var/log/gitlab/nginx/gitlab_registry_error.log` contains a log of NGINX errors for the Container Regsitry.
+
+Below is the default GitLab NGINX access log format:
+
+```plaintext
+$remote_addr - $remote_user [$time_local] "$request" $status $body_bytes_sent "$http_referer" "$http_user_agent"
+```
+
 [repocheck]: repository_checks.md
 [Rack Attack]: ../security/rack_attack.md
 [Rate Limit]: ../user/admin_area/settings/rate_limits_on_raw_endpoints.md