recovery 调试
Android 启动后，会先运行 bootloader。 Bootloader 会根据某些判定条件决定是否进入 recovery
模式。 Recovery 模式会装载 recovery 分区，该分区包含 recovery.img。 Recovery.img 包含了标准
内核(和 boot.img 中的内核相同)以及 recovery 根文件系统。
开启recovery 模式下的 adb调试
## Troubleshooting
### `adb devices` doesn't show the device.
$ adb devices
List of devices attached
* Ensure `adbd` is built and running.
By default, `adbd` is always included into recovery image, as `/system/bin/adbd`. `init` starts
`adbd` service automatically only in debuggable builds. This behavior is controlled by the recovery
specific `/init.rc`, whose source code is at `bootable/recovery/etc/init.rc`.
The best way to confirm a running `adbd` is by checking the serial output, which shows a service
start log as below.
[ 18.961986] c1 1 init: starting service 'adbd'...
* Ensure USB gadget has been enabled.
If `adbd` service has been started but device not shown under `adb devices`, use `lsusb(8)` (on
host) to check if the device is visible to the host.
`bootable/recovery/etc/init.rc` disables Android USB gadget (via sysfs) as part of the `fs` action
trigger, and will only re-enable it in debuggable builds (the `on property` rule will always run
_after_ `on fs`).
on fs
write /sys/class/android_usb/android0/enable 0
# Always start adbd on userdebug and eng builds
on property:ro.debuggable=1
write /sys/class/android_usb/android0/enable 1
start adbd
开启串口调试
编译单独
* Devices using recovery-as-boot (e.g. Pixels, which set BOARD\_USES\_RECOVERY\_AS\_BOOT)
# After setting up environment and lunch.
m -j bootimage
adb reboot bootloader
# Pixel devices don't support booting into recovery mode with `fastboot boot`.
fastboot flash boot
# Manually choose `Recovery mode` from bootloader menu.
* Devices with a separate recovery image (e.g. Nexus)
# After setting up environment and lunch.
mm -j && m ramdisk-nodeps && m recoveryimage-nodeps
adb reboot bootloader
# To boot into the new recovery image without flashing the recovery partition:
fastboot boot $ANDROID_PRODUCT_OUT/recovery.img