Source:

• GitLab Install
• GitLab’s repos

I. Creating a backup
sudo gitlab-rake gitlab:backup:create
 

II. Install and restore backup:
sudo aptitude install -y curl openssh-server ca-certificates
curl -s https://packages.gitlab.com/install/repositories/gitlab/gitlab-ee/script.deb.sh | sudo bash
sudo aptitude install gitlab-ee=10.7.3-ee.0
sudo mv 1526756133_2018_05_19_10.7.3-ee_gitlab_backup.tar /var/opt/gitlab/backups/.
sudo gitlab-ctl stop unicorn
sudo gitlab-ctl stop sidekiq
sudo gitlab-rake gitlab:backup:restore BACKUP=1526756133_2018_05_19_10.7.3-ee
sudo gitlab-ctl restart
sudo aptitude upgrade