Install according to the official documentation: https://www.gitlab.com.cn/installation/#centos-6
centos6 ：
1. lokkit is not installed, install lokkit after yum search lokkit
sudo yum install -y curl policycoreutils-python openssh-server cronie sudo lokkit -s http -s ssh
2. Install the mail client software postfix
sudo yum install postfix sudo service postfix start sudo chkconfig postfix on
3. Set up the yum repository
curl https://packages.gitlab.com/install/repositories/gitlab/gitlab-ee/script.rpm.sh | sudo bash
4. Really start installing gitlab
sudo EXTERNAL_URL="http://gitlab.example.com" yum -y install gitlab-ee
5. Due to network reasons, I completed steps 1 and 2 above, and then used gitlba Tsinghua mirror to install
https://mirror.tuna.tsinghua.edu.cn/help/gitlab-ce/
6. Then refer to https://yq.aliyun.com/articles/74395 for configuration startup
sudo vim /etc/gitlab/gitlab.rb # 修改默认的配置文件；external_url 'http://10.7.9.21'这条配置是web访问的url
sudo gitlab-ctl reconfigure # 然后启动服务；会安装一段时间其他操作
sudo gitlab-ctl start # 启动所有 gitlab 组件；
sudo gitlab-ctl stop # 停止所有 gitlab 组件；
sudo gitlab-ctl restart # 重启所有 gitlab 组件；
sudo gitlab-ctl status # 查看服务状态；
gitlab-rake gitlab:check SANITIZE=true --trace # 检查gitlab；
sudo gitlab-ctl tail # 查看日志；7. The browser accesses external_url, the first login will allow you to modify the password of the default account root
8. The rest is to operate the same as github
参考：
1、https://yq.aliyun.com/articles/74395
2、https://mirror.tuna.tsinghua.edu.cn/help/gitlab-ce/
3、https://www.gitlab.com.cn/installation/#centos-6