Media change : please insert the

Ubuntu-Server 16.04.1 执行 sudo apt install openssh-server 提示
Media change : please insert the disc labeled

解决办法如下：

• 编辑 /etc/apt/sources.list
  $ vi /etc/apt/sources.list
• 注释掉deb cdrom开头的那一行
  # deb cdrom:
• 更新deb仓库信息
  $ sudo apt update