85 lines
3.1 KiB
Markdown
85 lines
3.1 KiB
Markdown
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# FS Config Generator
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The `fs_config_generator.py` tool uses the platform `android_filesystem_config.h` and the
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`TARGET_FS_CONFIG_GEN` files to generate the following:
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* `fs_config_dirs` and `fs_config_files` files for each partition
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* `passwd` and `group` files for each partition
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* The `generated_oem_aid.h` header
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## Outputs
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### `fs_config_dirs` and `fs_config_files`
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The `fs_config_dirs` and `fs_config_files` binary files are interpreted by the libcutils
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`fs_config()` function, along with the built-in defaults, to serve as overrides to complete the
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results. The Target files are used by filesystem and adb tools to ensure that the file and directory
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properties are preserved during runtime operations. The host files in the `$OUT` directory are used
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in the final stages when building the filesystem images to set the file and directory properties.
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See `./fs_config_generator.py fsconfig --help` for how these files are generated.
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### `passwd` and `group` files
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The `passwd` and `group` files are formatted as documented in man pages passwd(5) and group(5) and
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used by bionic for implementing `getpwnam()` and related functions.
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See `./fs_config_generator.py passwd --help` and `./fs_config_generator.py group --help` for how
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these files are generated.
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### The `generated_oem_aid.h` header
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The `generated_oem_aid.h` creates identifiers for non-platform AIDs for developers wishing to use
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them in their native code. To do so, include the `oemaids_headers` header library in the
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corresponding makefile and `#include "generated_oem_aid.h"` in the code wishing to use these
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identifiers.
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See `./fs_config_generator.py oemaid --help` for how this file is generated.
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## Parsing
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See the documentation on [source.android.com](https://source.android.com/devices/tech/config/filesystem#configuring-aids) for details and examples.
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## Ordering
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Ordering within the `TARGET_FS_CONFIG_GEN` files is not relevant. The paths for files are sorted
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like so within their respective array definition:
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* specified path before prefix match
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* for example: foo before f*
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* lexicographical less than before other
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* for example: boo before foo
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Given these paths:
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paths=['ac', 'a', 'acd', 'an', 'a*', 'aa', 'ac*']
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The sort order would be:
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paths=['a', 'aa', 'ac', 'acd', 'an', 'ac*', 'a*']
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Thus the `fs_config` tools will match on specified paths before attempting prefix, and match on the
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longest matching prefix.
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The declared AIDs are sorted in ascending numerical order based on the option "value". The string
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representation of value is preserved. Both choices were made for maximum readability of the
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generated file and to line up files. Sync lines are placed with the source file as comments in the
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generated header file.
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## Unit Tests
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From within the `fs_config` directory, unit tests can be executed like so:
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$ python -m unittest test_fs_config_generator.Tests
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.............
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----------------------------------------------------------------------
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Ran 13 tests in 0.004s
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OK
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One could also use nose if they would like:
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$ nose2
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To add new tests, simply add a `test_<xxx>` method to the test class. It will automatically
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get picked up and added to the test suite.
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