For those who like to watch long videos, here is a screencast from the presentation I gave last night at *Denver Droids* on the Android boot process and application launching.
I watched this last night. I found it very interesting and well presented. Have you ever thought about getting into teaching about Android professionally? 😉😝 Seriously though, your pace, tone, use of illustrations, and timely, informative, yet brief tangents are all evidence you've mastered this kind of stuff. New Circle is lucky to have you. Great job.
Does PPID mean that the process was "forked" from the original? So as zygote gets forked each time for every new process, PPID 2 means the kthreadd gets also copied (forked) for every subsequent kernel process?
Dave Smith You mentioned the bootanimation is a daemon that is loaded before the applications and is a 1 shot. Could you change init to make it not one shot and could an app have permissions to start these processes again? In the list of processes at the end, it shows the adb daemon has started /system/bin/sh is this the way emulators have root access and you wouldn't see this on a normal device? (does this infer adb is different for emulators or init.d is different)
The boot animation is defined as a service in init.rc (android.googlesource.com/platform/system/core/+/android-5.1.1_r1/rootdir/init.rc), and you can see the "oneshot" keyword. This indicates that init will not attempt to restart the binary once it exits. You could remove the keyword and rebuild the image, but it wouldn't be very useful as the boot animation would just run continuously and you couldn't kill it! Any user process can invoke /system/bin/bootanimation, but it won't do much because the state is controlled by a system property (service.bootanim.exit), which is set by SurfaceFlinger during boot to kill the animation. With this property set, the bootanimation binary will immediately exist when started. You can play around with this in the emulator by clearing the prop and restarting the binary. I don't believe a user-build allows you to change the prop. The adbd will always spawn the shell, on any system, because you need to connect over ADB first (i.e. `adb shell`). It is also true that this is how root access is delegated in eng, userdebug, user builds. For example, running `adb root` first tells the daemon that the next `adb shell` should be given root instead of the shell user.
Hello Sir, a very great explanation, i have been looking all around and try to understand the process, but your video has helped me alot. i have an android phone, but my phone is going in boot loop and after showing MIUI it gives a black screen while white circle and middle which is in loop. Could you please explain on which file is corrupt. Also its going in recovery where it shows the NV data is corrupt
For those who like to watch long videos, here is a screencast from the presentation I gave last night at *Denver Droids* on the Android boot process and application launching.
I watched this last night. I found it very interesting and well presented. Have you ever thought about getting into teaching about Android professionally? 😉😝
Seriously though, your pace, tone, use of illustrations, and timely, informative, yet brief tangents are all evidence you've mastered this kind of stuff. New Circle is lucky to have you. Great job.
Thanks Dave !
Explanation of Zygote at 27:00 is very good.
Excellent! Thank you for explaining.
Good content and the way of explaining is excellent!
Brilliant tutorial on boot up process. Could you please make a video on debugging crash reports / stack traces.
Very good & informative, thanks
Excellent video, very easy to understand and well explained.
Excellent explanation ! Thank You
The best explanation ever
Thank you for your very detailed and helpful explaination.
Awesome excellent!!!!!!! Thank you for this
awesome, very informative, thanks!
Awesome explanation! Are slides available for this talk?
Very good talk, thank you for sharing !
I thank you very very much for the couse
Thanks, excellent presentation
Good content ❤
Does PPID mean that the process was "forked" from the original? So as zygote gets forked each time for every new process, PPID 2 means the kthreadd gets also copied (forked) for every subsequent kernel process?
Great work ..
Well Explained Thanks
Dave Smith You mentioned the bootanimation is a daemon that is loaded before the applications and is a 1 shot. Could you change init to make it not one shot and could an app have permissions to start these processes again?
In the list of processes at the end, it shows the adb daemon has started /system/bin/sh is this the way emulators have root access and you wouldn't see this on a normal device? (does this infer adb is different for emulators or init.d is different)
The boot animation is defined as a service in init.rc (android.googlesource.com/platform/system/core/+/android-5.1.1_r1/rootdir/init.rc), and you can see the "oneshot" keyword. This indicates that init will not attempt to restart the binary once it exits. You could remove the keyword and rebuild the image, but it wouldn't be very useful as the boot animation would just run continuously and you couldn't kill it!
Any user process can invoke /system/bin/bootanimation, but it won't do much because the state is controlled by a system property (service.bootanim.exit), which is set by SurfaceFlinger during boot to kill the animation. With this property set, the bootanimation binary will immediately exist when started. You can play around with this in the emulator by clearing the prop and restarting the binary. I don't believe a user-build allows you to change the prop.
The adbd will always spawn the shell, on any system, because you need to connect over ADB first (i.e. `adb shell`). It is also true that this is how root access is delegated in eng, userdebug, user builds. For example, running `adb root` first tells the daemon that the next `adb shell` should be given root instead of the shell user.
So in the x86 PC, BIOS, MBR, Bootloader are all separate. In mobile phones, its the Bootloader that contains all these 3?
Sir,thank you for this video.
But I have a question that "what is the function of boot image and how it is differ from bootloader"
Thanks for Sharing !
Hello Sir,
a very great explanation, i have been looking all around and try to understand the process, but your video has helped me alot.
i have an android phone, but my phone is going in boot loop and after showing MIUI it gives a black screen while white circle and middle which is in loop. Could you please explain on which file is corrupt.
Also its going in recovery where it shows the NV data is corrupt
Hi @Dave Smith. can you share the ppt?
I want to learn this for root android.Can it?
THX