A question about Android recovery disk image and partitions

Question

In this video, the host is trying to modify an existing TWRP disk image file and flash the modified image in his Moto G. What surprised me is the content of that TWRP recovery image. The video shows the contents of the TWRP recovery image as:




  1. zImage (Kernal)

  2. initrd.img (initial ramdisk)



How is that possible? I was under the impression that the kernel and the initial ramdisk reside in the /boot partition. He simply booted the image without giving any partition argument for fastboot:



sudo fastboot boot <recovery.img>


So, where would that disk image file go? /boot or /recovery? Flashing the kernel and its ramdisk (with init.rc script) into the boot partition makes sense, but I am confused because he was working with a recovery disk image, which he should have flashed into the /recovery partition. Does the recovery image also have its own kernel and ramdisk? I tried to download and see the contents of an Android recovery disk image by myself, but I couldn't open the .img file in Windows.


— Vinit Shandilya | Sources

Answer

fastboot boot does not perform a flash. From fastboot help:



usage: fastboot [ <option> ] <command>



commands:

  [...]

  flash <partition> [ <filename> ]

 Write a file to a flash partition.

  [...]

  boot <kernel> [ <ramdisk> [ <second> ] ]
  Download and boot kernel.



Does the recovery image also have its own kernel and ramdisk?




Yup. Recovery is essentially a miniature OS and boots similarly to the main boot image.


— Matthew Read | Sources

Q & A

Why does my phone automatically power off when there is still 2% battery?
One of my account can't login to google play
Remove Most Frequently Used Apps Container from Apps menu
Can I know who is changing Android's media volume?
linux kernel not seen from android filesystem?
Is there a way to improve S6 audio quality?
can fastboot be used to backup device?
HTC One M7 stuck on boot
Can I waked a sleeping Android without an app installed?
OTA update (Marshmallow) failing with "error" while installing it on a device running Android One
How does the "Format as internal storage" feature work in Android 6.0+?
Got stuck with a Pop-up on the main screen
Tasker App Factory Generated app - Not reacting to variable set %CLIP
Rooting Samsung Galaxy S3
How to choose my SD card type based on transfer speed?
Mic doesn't work during calls!
IS there any emoji keyboard available to support custom sticker?
Can't install TWRP on Note 4
Cyanogenmod: Google Play Services keeps crashing after update
How to tilt Google Maps in an emulator?

Topics

2D Engines   3D Engines   9-Patch   Action Bars   Activities   ADB   Advertisements   Analytics   Animations   ANR   AOP   API   APK   APT   Architecture   Audio   Autocomplete   Background Processing   Backward Compatibility   Badges   Bar Codes   Benchmarking   Bitmaps   Bluetooth   Blur Effects   Bread Crumbs   BRMS   Browser Extensions   Build Systems   Bundles   Buttons   Caching   Camera   Canvas   Cards   Carousels   Changelog   Checkboxes   Cloud Storages   Color Analysis   Color Pickers   Colors   Comet/Push   Compass Sensors   Conferences   Content Providers   Continuous Integration   Crash Reports   Credit Cards   Credits   CSV   Curl/Flip   Data Binding   Data Generators   Data Structures   Database   Database Browsers   Date &   Debugging   Decompilers   Deep Links   Dependency Injections   Design   Design Patterns   Dex   Dialogs   Distributed Computing   Distribution Platforms   Download Managers   Drawables   Emoji   Emulators   EPUB   Equalizers &   Event Buses   Exception Handling   Face Recognition   Feedback &   File System   File/Directory   Fingerprint   Floating Action   Fonts   Forms   Fragments   FRP   FSM   Functional Programming   Gamepads   Games   Geocaching   Gestures   GIF   Glow Pad   Gradle Plugins   Graphics   Grid Views   Highlighting   HTML   HTTP Mocking   Icons   IDE   IDE Plugins   Image Croppers   Image Loaders   Image Pickers   Image Processing   Image Views   Instrumentation   Intents   Job Schedulers   JSON   Keyboard   Kotlin   Layouts   Library Demos   List View   List Views   Localization   Location   Lock Patterns   Logcat   Logging   Mails   Maps   Markdown   Mathematics   Maven Plugins   MBaaS   Media   Menus   Messaging   MIME   Mobile Web   Native Image   Navigation   NDK   Networking   NFC   NoSQL   Number Pickers   OAuth   Object Mocking   OCR Engines   OpenGL   ORM   Other Pickers   Parallax List   Parcelables   Particle Systems   Password Inputs   PDF   Permissions   Physics Engines   Platforms   Plugin Frameworks   Preferences   Progress Indicators   ProGuard   Properties   Protocol Buffer   Pull To   Purchases   Push/Pull   QR Codes   Quick Return   Radio Buttons   Range Bars   Ratings   Recycler Views   Resources   REST   Ripple Effects   RSS   Screenshots   Scripting   Scroll Views   SDK   Search Inputs   Security   Sensors   Services   Showcase Views   Signatures   Sliding Panels   Snackbars   SOAP   Social Networks   Spannable   Spinners   Splash Screens   SSH   Static Analysis   Status Bars   Styling   SVG   System   Tags   Task Managers   TDD &   Template Engines   Testing   Testing Tools   Text Formatting   Text Views   Text Watchers   Text-to   Toasts   Toolkits For   Tools   Tooltips   Trainings   TV   Twitter   Updaters   USB   User Stories   Utils   Validation   Video   View Adapters   View Pagers   Views   Watch Face   Wearable Data   Wearables   Weather   Web Tools   Web Views   WebRTC   WebSockets   Wheel Widgets   Wi-Fi   Widgets   Windows   Wizards   XML   XMPP   YAML   ZIP Codes