Do NOT try this on a standard Synology DS415+ with 4GB of memory. You need at least 8GB to to run GitLab and still be able to use your Synology. I upgraded my DS415+ to 8GB which would have voided the warranty if it hadn't expired yet.

• Open DSM Package Center and install Docker.
  • Open DSM Control Panel and under “File Sharing” open “Shared Folder”.
  • Create a new shared folder with the name “gitlab” on Volume 1.
  • Hide this shared folder in “My Network Places”.
  • Disable the Recycle Bin.
• Open DSM Docker and under “Registry” download “gitlab/gitlab-ce”.
  • In the “Choose Tag” dialog box select “latest”.
• In DSM Docker under “Image” launch “gitlab/gitlab-ce”.
  • In the “General Settings” dialog box open the “Advanced Settings”.
  • Under “Volume” create and mount folder /volume1/gitlab/logs as /var/log/gitlab
  • Under “Volume” create and mount folder /volume1/gitlab/data as /var/opt/gitlab
  • Under “Volume” create and mount folder /volume1/gitlab/config as /etc/gitlab
  • Under “Port Settings” bind local port 8022 to container port 22
  • Under “Port Settings” bind local port 8080 to container port 80
  • Apply the settings and start the container (this takes a couple of minutes).
• Open http://example.com:8080/ and enter a new password for user ‘root’.

• Open http://example.com:8080/ and sign in as user ‘root’.
• Open “Admin Area” => “Settings” => “General” => “Visibility and access controls”.
• Configure “Custom Git clone URL for HTTP(S)” as “http://example.com:8080“.
• Open DSM Control Panel and under “Applications” open “Terminal & SNMP”.
• Enable the SSH service.
• Use an SSH client to connect as user ‘admin’ to the Synology.
• Use “sudo docker ps” to determine the ID of the running gitlab container.
• Use “sudo docker exec -it /bin/bash” to access the container.
• Edit the gitlab configuration with “vi /etc/gitlab/gitlab.rb”:
  • external_url "http://example.com:8080"
  • gitlab_rails['gitlab_ssh_host'] = 'example.com'
  • gitlab_rails['gitlab_shell_ssh_port'] = 8022
  • nginx['listen_port'] = 80
• Use “gitlab-ctl reconfigure“ to activate the modified settings.
• Wait a couple of minutes to allow GitLab to initialize after the reconfiguration.
• Open http://example.com:8080/ and check if GitLab functions correctly.

• To be documented ...