Raspbian系统更新默认禁用ssh服务

在2016-11-25日的更新中，系统默认对ssh服务禁用了。之前有朋友在我们的qq群里问过，当时帮他回答了，不过他也没有再反馈是否解决问题。所以，今天我就自己测试了下，并记录下操作分享给大家。先来看下官方的更新日志：

2017-02-16:
  * Chromium browser updated to version 56
  * Adobe Flash Player updated to version 24.0.0.221
  * RealVNC Server and Viewer updated to version 6.0.2 (RealVNC Connect)
  * Sonic Pi updated to version 2.11
  * Node-RED updated to version 0.15.3
  * Scratch updated to version 120117
  * Detection of SSH enabled with default password moved into PAM
  * Updated desktop GL driver to support use of fake KMS option
  * Raspberry Pi Configuration and raspi-config allow setting of fixed HDMI resolution
  * raspi-config allows enabling of serial hardware independent of serial terminal
  * Updates to kernel and firmware
  * Various minor bug fixes and usability and appearance tweaks
2017-01-11:
  * Re-release of the 2016-11-25 image with a FAT32-formatted boot partition
2016-11-25:
  * SSH disabled by default; can be enabled by creating a file with name "ssh" in boot partition
  * Prompt for password change at boot when SSH enabled with default password unchanged
  * Adobe Flash Player included
  * Updates to hardware video acceleration in Chromium browser
  * Greeter now uses background image from last set in Appearance Settings rather than pi user
  * Updated version of Scratch
  * Rastrack option removed from raspi-config and Raspberry Pi Configuration
  * Ability to disable graphical boot splash screen added to raspi-config and Raspberry Pi Configuration
  * Appearance Settings dialog made tabbed to work better on small screens
  * Raspberry Pi Configuration now requires current password to change password
  * Various small bug fixes
  * Updated firmware and kernel

上面2016-11-25日的更新中，第一条就说默认ssh是被禁用了，如果要启用它需要在boot分区添加一个名字为ssh的文件。这里没有说这个文件的内容，其实就是一个空文件就可以。为了方便不能访问树莓派官网的朋友，我把镜像上传到了百度云上这是链接：https://pan.baidu.com/s/1hsiKweg