I have a gitlab group with some repositories and issues and I would like to make a backup of the whole group.
I was looking at the doc. from gitlab but it's confusing for me and I don't know where to start.
When I run this command it creates a 300Kb .tar file but the group is larger than that, where do I specify the URL of the gitlab group I want to backup?
sudo gitlab-backup create
When using the SaaS service on gitlab.com there isn't really a procedure to "backup" your data. Generally, you rely on GitLab to ensure your data is always available on gitlab.com
There is documentation for backup and restore processes but this applies to self-hosted GitLab instances only. (this is probably why you aren't able to figure out using the gitlab backup tools because they are intended for self-hosted instances only).
If you still want to backup your data that is on gitlab.com, one option might be to do a file-based export of a group. However, this procedure is deprecated and import support may be removed entirely in the future. Another option may be to "migrate" your groups following the group migration documentation onto a self-hosted GitLab instance, then backup that self-hosted instance using the backup and restore process linked above.
Other than this, it is also possible to export projects to create zip archives that can later be imported to GitLab. This will include repository data, issues, etc. You can't do this in a single operation for your whole group, but you can export each project in your group individually, if you want.