用 ubuntu 安装博客，前面都通顺，但执行了 install ghost 就会提示

ost@VM-0-10-ubuntu:/var/www/ghost$ ghost install
✔ Checking system Node.js version
✖ Checking logged in user
✔ Checking current folder permissions
✔ Checking operating system compatibility
✔ Checking for a MySQL installation
✔ Checking memory availability
One or more errors occurred.

1) Checking logged in user

Message: You can't install Ghost with a user called ghost. Please use a different user(name).
Help: https://docs.ghost.org/docs/install#section-create-a-new-user

Debug Information:
OS: Ubuntu, v16.04
Node Version: v6.14.1
Ghost-CLI Version: 1.7.1
Environment: production
Command: 'ghost install'

Try running ghost doctor to check your system for known issues.

Please refer to https://docs.ghost.org/v1/docs/troubleshooting#section-cli-errors for troubleshooting.

我创建了一个非 root 用户的 ghost 用户，第一次授权了 root 权限，依旧提示上面的错误问题，第二次没有授权 root 可依旧提示上面的问题，真的无法解决了，求帮助