Migrating GitLab from Docker (installed on Synology DiskStation) to a Ubuntu VM

I have been tasked with migrating our current setup of GitLab which resides in Docker on our NAS Synology DiskStation appliance to a new Ubuntu VM.

The person who initiated this move has created a backup file xxx_gitlab_backup.tar in which they are under the impression contains all necessary information to fully migrate all data from our current instance. I have been told the migration must be to the same version of GitLab as is installed in Docker (8.6.2), as such I have installed that version on to our Ubuntu 12.04 server. As far as I can tell the installation was successful.

I then tried to restore the backup (which was placed in var/opt/gitlab/backups) and it appeared to unpack and start the restoration process. Having said that, when the webserver is accessed - it appeared to be a fresh/blank install as it asked for the root password to be changed (as if it was a first time start-up).

In various documentation I’ve seen it appears that creating a backup for migration requires (in addition to the .tar file) the manual copying of various configuration/system files which I assume are not included in the single backup file. Is this correct or is the single .tar file sufficient? As I am not proficient with UNIX/CLI any documentation to backup from docker and migrate to the new VM would be much appreciated. As it stand now, all users are still pointed to our Synology DiskStation running GitLab via Docker.

One last question, is there a benefit to installing docker on the VM and then using a containerized version of GitLab or would best practice be installing it by itself on the VM without Docker?

It appears I have been successful in at least migrating the data over as the webserver which initially appeared to be blank/have no backups restored is now giving me a “500 - Whoops, something went wrong on our end.”.

It would seem from reading this post (https://gitlab.com/gitlab-org/gitlab-ce/issues/17873#note_12117671) that the issue is that the backup I restored is missing the ‘db_key_base’ string found in ‘/etc/gitlab/gitlab-secrets.json’. The suggestion was to copy the ‘db_key_base’ from the old instance to the new one. Can someone explain how this is done? Is it the ‘sudp cp /etc/gitlab/gitlab-secrets.json [destination-folder]’ command? Once the string/secrets file has been copied, can I just run ‘sudo gitlab-ctl reconfigure’ and expect everything to be up and running?