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Magisk/docs/guides.md
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Developer Guides

Please read through Magisk Details before reading the following guides. If you are developing a module, pay extra attention to the Magic Mount section.

Magisk Modules

A Magisk module is a folder placed in /data/adb/modules with a structure below:

/data/adb/modules
├── .
├── .
|
├── $MODID                  <--- The folder is named with the ID of the module
│   │
│   │      *** Module Identity ***
│   │
│   ├── module.prop         <--- This files stores the metadata of the module
│   │
│   │      *** Status files ***
│   │
│   ├── skip_mount          <--- If exists, Magisk will NOT mount your files
│   ├── disable             <--- If exists, the module will be disabled
│   ├── remove              <--- If exists, the module will be removed next reboot
│   │
│   │      *** Scripts ***
│   │
│   ├── post-fs-data.sh     <--- This script will be executed in post-fs-data
│   ├── service.sh          <--- This script will be executed in late_start service
|   ├── uninstall.sh        <--- This script will be executed when Magisk removes your module
│   │
│   │      *** Resetprop Files ***
│   │
│   ├── system.prop         <--- This file will be loaded as system properties by resetprop
│   │
│   │      *** Module contents ***
│   │
│   ├── system              <--- This folder will be Magic Mounted if skip_mount does not exists
│   │   ├── .
│   │   ├── .
│   │   └── .
│   │
│   │      *** Auto Generated by Magisk ***
│   │
│   ├── vendor              <--- A symlink to $MODID/system/vendor
│   ├── product             <--- A symlink to $MODID/system/product
│   │
│   │      *** Others ***
│   │
│   ├── .                   <--- Any additional files / folders are allowed
│   └── .
|
├── another_module
│   ├── .
│   └── .
├── .
├── .

As long as a folder follows the structure above, it will be recognized as a module.

Here is the strict format of module.prop:

id=<string>
name=<string>
version=<string>
versionCode=<int>
author=<string>
description=<string>
  • id has to match this regular expression: ^[a-zA-Z][a-zA-Z0-9._-]+$
    ex: ✓ a_module, ✓ a.module, ✓ module-101, ✗ a module, ✗ 1_module, ✗ -a-module
    This is the unique identifier of your module. You should not change it once published.
  • versionCode has to be an integer. This is used to compare versions
  • Others that isn't mentioned above can be any single line string.

Magisk Module Installer

The official Magisk Module installer is hosted here.

That repo is a starting point for creating a Magisk module installer zip. Here are some details:

  • You will found out that META-INF/com/google/android/update-binary is a dummy file. If you are creating a module locally for personal usage or testing, download the latest installer module_installer.sh and replace update-binary with the script
  • The next thing to do is to modify module.prop to provide information about your module
  • Finally, modify install.sh to fit your need. The script is heavily documented so you should know what to do.
  • (Optional) If you want to run custom uninstallation logic when your module is removed, add a new file uninstall.sh to the root of the installer
  • Windows users aware!! The line endings of all text files should be in the Unix format. Please use advanced text editors like Sublime, Atom, Notepad++ etc. to edit ALL text files, NEVER use Windows Notepad.

Submit Modules

You can submit a module to Magisk-Module-Repo so users can download your module directly in Magisk Manager. Before submitting, follow the instructions in the previous section to create a valid installer for your module. You can then create a request for submission via this link: submission.

  • When your module is downloaded with Magisk Manager, META-INF/com/google/android/update-binary will be forcefully replaced with the latest module_installer.sh to make sure all installation uses the latest scripts.
  • Since update-binary will be replaced, this means that all modules in the repo are expected to follow how the installation framework works: the installation framework will load your install.sh script and run the corresponding callbacks.
  • This also means that you should NOT add custom logic in update-binary as they will simply be ignored.

Boot Scripts

In Magisk, you can run boot scripts in 2 different modes: post-fs-data and late_start service mode.

  • post-fs-data mode
    • This stage is BLOCKING. Boot process is paused before execution is done, or 10 seconds has passed.
    • Scripts run before any modules are mounted. This allows a module developer to dynamically adjust their modules before it gets mounted.
    • This stage happens before Zygote is started, which pretty much means everything in Android
    • Run scripts in this mode only if necessary!
  • late_start service mode
    • This stage is NON-BLOCKING. Your script runs in parallel along with the booting process.
    • This is the recommended stage to run most scripts!

In Magisk, there are also 2 kinds of scripts: general scripts and module scripts.

  • General Scripts
    • Placed in /data/adb/post-fs-data.d or /data/adb/service.d
    • Only executed if the script is executable (execution permissions, chmod +x script.sh)
    • Scripts in post-fs-data.d runs in post-fs-data mode, and scripts in service.d runs in late_start service mode.
    • Will still be executed when Core-Only mode is enabled.
    • Modules should NOT add general scripts since it violates encapsulation
  • Module Scripts
    • Placed in the folder of the module
    • Only executed if the module is enabled
    • post-fs-data.sh runs in post-fs-data mode, and service.sh runs in late_start service mode.
    • Will NOT be executed when Core-Only mode is enabled (all modules are disabled)
    • Modules require boot scripts should ONLY use module scripts instead of general scripts

Magisk's internal busybox's path $BBPATH is always prepended in PATH. This means all commands you call in scripts are always using busybox unless the applet is not included. This makes sure that your script always run in a predictable environment and always have the full suite of commands regardless of which Android version it is running on.

Root Directory Overlay System

Since / is read-only in system-as-root devices, Magisk provides an overlay system, allowing developers to patch files / add new rc scripts. Additional files shall be placed in the overlay.d folder in the ramdisk, and they will have the following restrictions:

  • All *.rc files in overlay.d will be read and concatenated AFTER init.rc
  • Replacing existing files are allowed.
    e.g. you can replace /res/random.png by adding the file overlay.d/res/random.png
  • Non-existing files will be ignored (with exceptions detailed in the next point).
    e.g. overlay.d/new_file will be ignored if /new_file does not exist
  • Additional files in overlay.d/sbin is allowed as they will be copied into Magisk's sbin overlay.
    e.g. overlay.d/sbin/libfoo.ko will be copied to /sbin/libfoo.ko.

Remove Files

How to remove a file systemless-ly? To actually make the file disappear is complicated (possible, not worth the effort). Replacing it with a dummy file should be good enough! Create an empty file with the same name and place it in the same path within a module, it shall replace your target file with a dummy file.

Remove Folders

Same as mentioned above, actually making the folder disappear is not worth the effort. Replacing it with an empty folder should be good enough! A handy trick for module developers is to add the folder you want to remove into the REPLACE list within install.sh. If your module doesn't provide a corresponding folder, it will create an empty folder, and automatically add .replace into the empty folder so the dummy folder will properly replace the one in /system.