前置条件:
1 android nexue 5 手机一部
2 android L最新rom包
android L rom下载地址
https://developers.google.com/fit/preview#flash_your_nexus_5_or_nexus_7
过程：
下载完成后解压缩，这个包需要使用 fastboot工具，不是原来的zip卡刷包，好在里面的脚本文件
都已经写好了，如下图：
连接好手机和电脑，笔者是在ubuntu下的进行刷机，以下是刷机过程
nexus 5 手机需要进入到fastboot的模式，进入方式 按下开机键+音量上下键（也就是要按下音量键中间的部分）
在手机的 fastboot模式，执行下面的命令
root@ubuntu:~/Desktop/hammerhead-lpv81c# ls
bootloader-hammerhead-hhz11k.img flash-base.sh
flash-all.bat p_w_picpath-hammerhead-lpv81c.zip
flash-all.sh radio-hammerhead-m8974a-2.0.50.2.08.img
root@ubuntu:~/Desktop/hammerhead-lpv81c# ./flash-all.sh
sending 'bootloader' (2508 KB)...
OKAY [ 0.543s]
writing 'bootloader'...
OKAY [ 0.494s]
finished. total time: 1.037s
rebooting into bootloader...
OKAY [ 0.040s]
finished. total time: 0.040s
sending 'radio' (45505 KB)...
OKAY [ 6.213s]
writing 'radio'...
OKAY [ 3.118s]
finished. total time: 9.332s
rebooting into bootloader...
OKAY [ 0.044s]
finished. total time: 0.044s
archive does not contain 'boot.sig'
archive does not contain 'recovery.sig'
archive does not contain 'system.sig'
--------------------------------------------
Bootloader Version...: HHZ11k
Baseband Version.....: M8974A-2.0.50.2.08
Serial Number........: 06ea489d00e2a439
--------------------------------------------
checking product...
OKAY [ 0.101s]
checking version-bootloader...
OKAY [ 0.099s]
checking version-baseband...
OKAY [ 0.100s]
sending 'boot' (8754 KB)...
OKAY [ 1.420s]
writing 'boot'...
OKAY [ 0.754s]
sending 'recovery' (9412 KB)...
OKAY [ 1.516s]
writing 'recovery'...
OKAY [ 0.791s]
erasing 'system'...
OKAY [ 0.969s]
sending 'system' (682924 KB)...
OKAY [103.092s]
writing 'system'...
OKAY [ 46.568s]
erasing 'userdata'...
OKAY [ 8.677s]
formatting 'userdata' partition...
Creating filesystem with parameters:
Size: 13725835264
Block size: 4096
Blocks per group: 32768
Inodes per group: 8144
Inode size: 256
Journal blocks: 32768
Label:
Blocks: 3351034
Block groups: 103
Reserved block group size: 823
Created filesystem with 11/838832 inodes and 93654/3351034 blocks
sending 'userdata' (137318 KB)...
writing 'userdata'...
OKAY [ 38.505s]
erasing 'cache'...
OKAY [ 0.613s]
formatting 'cache' partition...
Creating filesystem with parameters:
Size: 734003200
Block size: 4096
Blocks per group: 32768
Inodes per group: 7472
Inode size: 256
Journal blocks: 2800
Label:
Blocks: 179200
Block groups: 6
Reserved block group size: 47
Created filesystem with 11/44832 inodes and 5813/179200 blocks
sending 'cache' (13348 KB)...
writing 'cache'...
OKAY [ 3.278s]
rebooting...
finished. total time: 207.000s
root@ubuntu:~/Desktop/hammerhead-lpv81c#
注意：fastboot刷机界面很不友好，比如
fastboot -w update p_w_picpath-hammerhead-lpv81c.zip
这个命令执行过程，没有任何提示，并且时间很长，如果是初次刷机，有可能认为是刷机失败了
需要耐心等待一会儿
开机体验：
android L第一次开机速度奇慢，开机动画出现以后，等了大概5分钟，让笔者甚至怀疑是不是刷错
rom包了。在最后要放弃的时间，才出现了配置界面，发现rom包没有问题，估计是art模式转换的
时间太长了，但是好歹做个进度条提示，光一个开机动画转啊转，实在是让人很难忍受。