获取证书步骤不叙述，nginx无法启动问题参考 https://www.jianshu.com/p/2f77a52458db

1、打开gitlab.rb 更改配置

vi /etc/gitlab/gitlab.rb
external_url "https://your.domain.com"
# /etc/ssl/your.domain.com这个是你存储ssl证书的路径，自定义
nginx['ssl_certificate'] = "/etc/ssl/your.domain.com/fullchain.pem"
nginx['ssl_certificate_key'] = "/etc/ssl/your.domain.com/privkey.key"
#（可选）强制HTTP重定向到HTTPS：
nginx['redirect_http_to_https'] = true
# 配置NGINX监听端口：
nginx['listen_port'] = 443
nginx['listen_https'] = true

2、应用配置并重启GitLab

gitlab-ctl reconfigure
gitlab-ctl restart