--- /dev/null
+Most of the functionality that dracut implements are actually implemented
+by dracut modules. Dracut modules live in modules.d, and have the following
+structure:
+
+dracut_install_dir/modules.d/
+ 00modname/
+ install
+ check
+ <other files as needed by the hook>
+
+00modname: The name of the module prefixed by a two-digit numeric sort code.
+ The numeric code must be present and in the range of 00 - 99.
+ Modules with lower numbers are installed first. This is important
+ because the dracut install functions (which install files onto
+ the initrd) refuse to overwrite already installed files. This makes
+ it easy for an earlier module to override the functionality of a
+ later module, so that you can have a distro or system specific
+ module override or modify the functionality of a generic module
+ without having to patch the mode generic module.
+
+install: dracut sources this script to install the functionality that a
+ module implements onto the initrd. For the most part, this amounts
+ to copying files from the host system onto the initrd in a controlled
+ manner. dracut supplies several install functions that are
+ specialized for different file types. Browse through dracut-functions
+ fore more details. dracut also provides a $moddir variable if you
+ need to install a file from the module directory, such as an initrd
+ hook, a udev rule, or a specialized executable.
+
+check: Dracut calls this program to check and see if a module can be installed
+ on the initrd.
+
+ When called without options, check should check to make sure that
+ any files it needs to install into the initrd from the host system
+ are present. It should exit with a 0 if they are, and a 1 if they are
+ not.
+
+ When called with -h, it should perform the same check that it would
+ without any options, and it should also check to see if the
+ functionality the module implements is being used on the host system.
+ For example, if this module handles installing support for LUKS
+ encrypted volumes, it should return 0 if all the tools to handle
+ encrpted volumes are available and the host system has the root
+ partition on an encrypted volume, 1 otherwise.
+
+ Check may take additional options in the future.
+ We will most likely grow a module dependency checking system in the
+ near future, and check will need to handle a -d option when we do.
+
+Any other files in the module will not be touched by dracut directly.
+
+You are encouraged to provide a README that descrobes what the module is for.
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