ERROR: This AVD's configuration is missing a kernel file

emulator: ERROR: This AVD's configuration is missing a kernel file! Please ensure the file "kernel-ranchu" is in the same location as your system image.
emulator: ERROR: ANDROID_SDK_ROOT is undefined



When you try to launch a emulator device with arm image, you might got such error.
The key point to fix it is to ensure that the corresponding arm system image installed(same to the image you selected when create your virtual image,
you can check http://lengerrong.blogspot.com/2017/04/failure-installfailednomatchingabis.html).

For my case, I have to ensure ARM EABI v7a System Image Installed.
 












Once the correct image installed, the virtual device can be run well.
PS: run arm image on x86 host, the speed will be 10x lower.

Run emulator command:
C:\Users\lenger\AppData\Local\Android\Sdk\tools\emulator.exe -netdelay none -netspeed full -avd 24