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Dracut is the tool used by desktop distributions to build initrds. In the embedded world, it can be very useful, too, for instance when wanting to create an initramfs for a system recovery mode. Whereas it is definitively possible to achieve this with buildroot, the process is to have a dedicated buildroot configuration for that, and perform a full build. Instead of doing that, dracut can pick the needed binaries/shared libraries, configuration files, or kernel modules from the 'target' directory. The advantage is to save build time, and also to have a consistency between the packages versions taken for the recovery and the production filesystem. The principle of dracut is based on the so-called 'dracut modules'. The modules determine what will be included in the initramfs. For example, one of dracut's modules checks the kernel modules that are included and also includes the corresponding firmware blobs. On the host, they are on host/lib/dracut/modules.d Each directory as a prefix number for the order of execution, and at least a "module-setup.sh" script. Dracut sources all of them, and typically calls the "check()" function, which is the placeholder for required binaries (that are aimed to be polulated in the initrd), then the "depends()" function, that lists other modules to depend on, and the "install()" function, that makes the actual work. Dracut was initially thought to work with systems using systemd, but it can also work without it. Do to so, every "systemd-xxx" module must be disabled in the dracut configuration file. For convenience, the 05busybox-init module is provided, to support busybox init system. Note that this module should *not* be enabled when using systemd init. It is therefore only installed if busybox init is selected. Musl and uClibc make assumptions about the existence of some symlinks that are not discoverable with readelf. Therefore, another module 05libc-links is provided that creates those links. The module is installed regardless of which libc is used - the script itself discovers if the links need to be installed based on which libc is found. Signed-off-by: Thierry Bultel <thierry.bultel@linatsea.fr> [arnout@mind.be: many changes] Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be> Cc: Adam Duskett <aduskett@gmail.com> [yann.morin.1998@free.fr: some additional fixups] Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>
Buildroot is a simple, efficient and easy-to-use tool to generate embedded Linux systems through cross-compilation. The documentation can be found in docs/manual. You can generate a text document with 'make manual-text' and read output/docs/manual/manual.text. Online documentation can be found at http://buildroot.org/docs.html To build and use the buildroot stuff, do the following: 1) run 'make menuconfig' 2) select the target architecture and the packages you wish to compile 3) run 'make' 4) wait while it compiles 5) find the kernel, bootloader, root filesystem, etc. in output/images You do not need to be root to build or run buildroot. Have fun! Buildroot comes with a basic configuration for a number of boards. Run 'make list-defconfigs' to view the list of provided configurations. Please feed suggestions, bug reports, insults, and bribes back to the buildroot mailing list: buildroot@buildroot.org You can also find us on #buildroot on OFTC IRC. If you would like to contribute patches, please read https://buildroot.org/manual.html#submitting-patches