forked from openkylin/platform_build
fs_config: Update docs
1. Convert to README.md 2. Sync come content with the updates on source.android.com 3. fs_config uses bionic/libc/kernel/uapi/linux/capability.h, not system/core/include/private/android_filesystem_capability.h as the capability header, so update the documentation accordingly. Test: n/a Change-Id: I24a084d7a804d3f5d2259cfcea85b8ff4e79d290
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Tom Cherry
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_____ _____ _____ _____ __ __ _____
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/ _ \/ __\/ _ \| _ \/ \/ \/ __\
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| _ <| __|| _ || | || \/ || __|
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\__|\_/\_____/\__|__/|_____/\__ \__/\_____/
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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 fs_config_dirs and fs_config_files files for each
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partition, as well as passwd and group files, and the generated_oem_aid.h header.
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The fs_config_dirs and fs_config_files binary files are interpreted by the libcutils fs_config()
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function, along with the built-in defaults, to serve as overrides to complete the results. The
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Target files are used by filesystem and adb tools to ensure that the file and directory properties
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are preserved during runtime operations. The host files in the ${OUT} directory are used in the
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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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The passwd and group files are formatted as documented in man pages passwd(5) and group(5) and used
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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 these
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files are generated.
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The generated_oem_aid.h creates identifiers for non-platform AIDs for developers wishing to use them
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in their native code. To do so, include the oemaids_headers header library in the corresponding
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makefile and #include "generated_oem_aid.h" in the code wishing to use these identifiers.
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See ./fs_config_generator.py oemaid --help for how this file is generated.
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The parsing of the TARGET_FS_CONFIG_GEN files follows the Python ConfigParser specification, with
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the sections and fields as defined below. There are two types of sections, both sections require all
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options to be specified. The first section type is the "caps" section.
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The "caps" section follows the following syntax:
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[path]
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mode: Octal file mode
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user: AID_<user>
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group: AID_<group>
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caps: cap*
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Where:
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[path]
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The filesystem path to configure. A path ending in / is considered a dir,
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else its a file.
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mode:
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A valid octal file mode of at least 3 digits. If 3 is specified, it is
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prefixed with a 0, else mode is used as is.
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user:
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Either the C define for a valid AID or the friendly name. For instance both
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AID_RADIO and radio are acceptable. Note custom AIDs can be defined in the
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AID section documented below.
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group:
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Same as user.
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caps:
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The name as declared in
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system/core/include/private/android_filesystem_capability.h without the
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leading CAP_. Mixed case is allowed. Caps can also be the raw:
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* binary (0b0101)
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* octal (0455)
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* int (42)
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* hex (0xFF)
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For multiple caps, just separate by whitespace.
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It is an error to specify multiple sections with the same [path] in different
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files. Note that the same file may contain sections that override the previous
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section in Python versions <= 3.2. In Python 3.2 it's set to strict mode.
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The next section type is the "AID" section, for specifying OEM specific AIDS.
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The AID section follows the following syntax:
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[AID_<name>]
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value: <number>
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Where:
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[AID_<name>]
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The <name> can contain characters in the set uppercase, numbers
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and underscores.
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value:
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A valid C style number string. Hex, octal, binary and decimal are supported.
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See "caps" above for more details on number formatting.
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It is an error to specify multiple sections with the same [AID_<name>]. With
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the same constraints as [path] described above. It is also an error to specify
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multiple sections with the same value option. It is also an error to specify a
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value that is outside of the inclusive OEM ranges:
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* AID_OEM_RESERVED_START(2900) - AID_OEM_RESERVED_END(2999)
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* AID_OEM_RESERVED_2_START(5000) - AID_OEM_RESERVED_2_END(5999)
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as defined by system/core/include/private/android_filesystem_config.h.
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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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** ie foo before f*
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* lexicographical less than before other
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** ie 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 generated
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file and to line up files. Sync lines are placed with the source file as comments in the generated
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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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@ -0,0 +1,84 @@
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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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