官方文档
https://azure.microsoft.com/en-gb/documentation/articles/virtual-machines-linux-use-root-privileges/
教程
How to enable root access on Microsoft Azure Cloud.
1. Login via ssh using your sudo user
2. Now login as root user
sudo su -
3. check if root access is set (LOCK means that root access is disabled)
[root@Linux ~]# grep root /etc/shadow root:*LOCK*:14600::::::
4. enable root access (as root user enter command passwd)
[root@Linux ~]# passwd
now enter your password and root access is enabled, you can check this by using command “grep root /etc/shadow”