下载 raspbian jessie lite（https://www.raspberrypi.org/downloads/raspbian/）（无GUI版本），用一个老旧的2GB内存卡，烧录，空间都剩余800M左右。
最喜欢无GUI版本，命令行舒服。
1.烧录SD卡
$ cd 下载
$ sudo dd if=2016-xx-xx-raspbian-jessie-lite.img of=/dev/sdb bs=4M
//最新的目前是什么版本我已经搞不清楚了。
2.配置WIFI和连接密码
烧录完成之后，重新插拔SD卡。
然后看到有个1.3G的盘子里，一堆的Linux文件。
/etc/wpa_supplicant/wpa_supplicant.conf这个文件才是配置wifi和密码的。
sudo gedit /etc/wpa_supplicant/wpa_supplicant.conf
在文件的最后一行之后追加：
network={
ssid="testing"
psk="testingPassword"
}
有些同学，咳咳，那什么，自己家的wifi名字起得太长了，怕拼错的，ubuntu或者mac下可以用iwconfig命令获取一下，然后ctrl+shift+C拷贝一下，再写入到这个文件中。
3.启用ssh
a.在那个盘子下创建一个空白文件即可。
sudo vi etc/SSHFLAG
b.修改一个文件/etc/rc.local 追加如下代码在第一行。
if [ -e /etc/SSHFLAG ]; then
/usr/sbin/update-rc.d -f ssh defaults
/bin/rm /etc/SSHFLAG
/sbin/shutdown -r now
fi
从电脑上拔掉sd卡，插RPi上，开机。
c.启动后，等待重启（也许两分钟），这之后你可以ping到RPi的IP，如果确定，关闭RPi，拔掉SD卡，再次编辑文件/etc/rc.local与电脑。
插入如下代码，到第一行。
sudo vi /etc/init.d/ssh start
4.使用nmap扫描 局域网中 是否存在树莓派设备
$ sudo nmap 192.168.199.1-255
Starting Nmap 6.47 ( http://nmap.org ) at 2016-12-19 01:01 CST
Nmap scan report for Hiwifi.lan (192.168.199.1)
Host is up (0.00088s latency).
Not shown: 993 closed ports
PORT STATE SERVICE
53/tcp open domain
80/tcp open http
81/tcp open hosts2-ns
82/tcp open xfer
83/tcp open mit-ml-dev
443/tcp open https
5000/tcp open upnp
MAC Address: D4:EE:07:13:C9:46 (Hiwifi Co.)
Nmap scan report for 192.168.199.117
Host is up (0.0013s latency).
Not shown: 999 closed ports
PORT STATE SERVICE
22/tcp open ssh
MAC Address: B8:27:EB:46:73:43 (Raspberry Pi Foundation)
Nmap scan report for android-a3929929ec50096a.lan (192.168.199.207)
Host is up (0.0022s latency).
All 1000 scanned ports on android-a3929929ec50096a.lan (192.168.199.207) are closed
MAC Address: 80:41:4E:D5:EE:13 (BBK Electronics)
Nmap scan report for raspberrypi.lan (192.168.199.218)
Host is up (0.0013s latency).
Not shown: 999 closed ports
PORT STATE SERVICE
22/tcp open ssh
MAC Address: B8:27:EB:13:26:16 (Raspberry Pi Foundation)
Nmap scan report for wei-MacBookAir.lan (192.168.199.124)
Host is up (0.0000070s latency).
Not shown: 999 closed ports
PORT STATE SERVICE
22/tcp open ssh
Nmap done: 255 IP addresses (5 hosts up) scanned in 193.37 seconds'
单独扫描117这个ip，查看是否开启了ssh的22端口。
$ sudo nmap -O 192.168.199.117
[sudo] wei 的密码：
Starting Nmap 6.47 ( http://nmap.org ) at 2016-12-19 01:23 CST
Nmap scan report for raspberrypi.lan (192.168.199.117)
Host is up (0.0050s latency).
Not shown: 999 closed ports
PORT STATE SERVICE
22/tcp open ssh
MAC Address: B8:27:EB:46:73:43 (Raspberry Pi Foundation)
Device type: general purpose
Running: Linux 3.X
OS CPE: cpe:/o:linux:linux_kernel:3
OS details: Linux 3.11 - 3.14
Network Distance: 1 hop
OS detection performed. Please report any incorrect results at http://nmap.org/submit/ .
Nmap done: 1 IP address (1 host up) scanned in 21.84 seconds'
日志上显示已经开启了这个端口，接下来。我们ssh登录一下吧。
$ ssh pi@192.168.199.117
'The authenticity of host 192.168.199.117 (192.168.199.117) cant be established.
ECDSA key fingerprint is SHA256:337sCVUu6oxJn7sCEy1VbNeijLqdajX/JSGkiCC7jL0.
Are you sure you want to continue connecting (yes/no)? yes
Warning: Permanently added '192.168.199.117' (ECDSA) to the list of known hosts.
pi@192.168.199.117''s password:
The programs included with the Debian GNU/Linux system are free software;
the exact distribution terms for each program are described in the
individual files in /usr/share/doc/*/copyright.
Debian GNU/Linux comes with ABSOLUTELY NO WARRANTY, to the extent
permitted by applicable law.
Last login: Fri Nov 25 18:01:05 2016
SSH is enabled and the default password for the 'pi' user has not been changed.
This is a security risk - please login as the 'pi' user and type 'passwd' to set a new password.
pi@raspberrypi:~ $ cpuinfo
-bash: cpuinfo: command not found
pi@raspberrypi:~ $ cpuinfo
-bash: cpuinfo: command not found
pi@raspberrypi:~ $ lscpu
Architecture: armv7l
Byte Order: Little Endian
CPU(s): 4
On-line CPU(s) list: 0-3
Thread(s) per core: 1
Core(s) per socket: 4
Socket(s): 1
Model name: ARMv7 Processor rev 4 (v7l)
CPU max MHz: 1200.0000
CPU min MHz: 600.0000