Buildroot knows about a number of well-known cross-compilation toolchains from Linaro for ARM, Sourcery CodeBench for ARM, x, PowerPC, and MIPS, and is capable of downloading them automatically, or it can be pointed to a custom toolchain, either available for download or installed locally. Our external toolchain support has been tested with toolchains from CodeSourcery and Linaro, toolchains generated by crosstool-NG , and toolchains generated by Buildroot itself. In general, all toolchains that support the sysroot feature should work.

If not, do not hesitate to contact the developers. We do not support toolchains or SDK generated by OpenEmbedded or Yocto, because these toolchains are not pure toolchains i. Instead these toolchains come with a very large set of pre-compiled libraries and programs.

Therefore, Buildroot cannot import the sysroot of the toolchain, as it would contain hundreds of megabytes of pre-compiled libraries that are normally built by Buildroot. We also do not support using the distribution toolchain i. This is because your distribution toolchain is not a "pure" toolchain i. If you want to generate a custom toolchain for your project, that can be used as an external toolchain in Buildroot, our recommendation is to build it either with Buildroot itself see Section 6.

The Buildroot internal toolchain option can be used to create an external toolchain. Here are a series of steps to build an internal toolchain and package it up for reuse by Buildroot itself or other projects. Then, we can trigger the build, and also ask Buildroot to generate a SDK. This will conveniently generate for us a tarball which contains our toolchain:. Save this tarball, as it is now the toolchain that you can re-use as an external toolchain in other Buildroot projects.

In those other Buildroot projects, in the Toolchain menu:. When using an external toolchain, Buildroot generates a wrapper program, that transparently passes the appropriate options according to the configuration to the external toolchain programs. Without these device files , your userspace applications would not be able to use the hardware devices, even if they are properly recognized by the Linux kernel. The init program is the first userspace program started by the kernel it carries the PID number 1 , and is responsible for starting the userspace services and programs for example: web server, graphical applications, other network servers, etc.

Buildroot allows to use three different types of init systems, which can be chosen from System configuration , Init system :. The solution recommended by Buildroot developers is to use the BusyBox init as it is sufficient for most embedded systems. systemd can be used for more complex situations.

Before attempting to modify any of the components below, make sure you have already configured Buildroot itself, and have enabled the corresponding package. Otherwise, Buildroot will start from a default BusyBox configuration file. To make subsequent changes to the configuration, use make busybox-menuconfig to open the BusyBox configuration editor. It is also possible to specify a BusyBox configuration file through an environment variable, although this is not recommended.

Refer to Section 8. To make subsequent changes to the configuration, use make linux-menuconfig to open the Linux configuration editor. Not all targets are always available, some settings in the. config file may hide some targets:. Cleaning: Explicit cleaning is required when any of the architecture or toolchain configuration options are changed. To delete all build products including build directories, host, staging and target trees, the images and the toolchain :.

To generate the manual:. Resetting Buildroot for a new target: To delete all build products as well as the configuration:.

If ccache is enabled, running make clean or distclean does not empty the compiler cache used by Buildroot. To delete it, refer to Section 8. Dumping the internal make variables: One can dump the variables known to make, along with their values:. Buildroot does not attempt to detect what parts of the system should be rebuilt when the system configuration is changed through make menuconfig , make xconfig or one of the other configuration tools.

In some cases, Buildroot should rebuild the entire system, in some cases, only a specific subset of packages. But detecting this in a completely reliable manner is very difficult, and therefore the Buildroot developers have decided to simply not attempt to do this. Instead, it is the responsibility of the user to know when a full rebuild is necessary.

As a hint, here are a few rules of thumb that can help you understand how to work with Buildroot:. If you get the same build error, then you are sure that the error is not related to partial rebuilds of packages, and if this error occurs with packages from the official Buildroot, do not hesitate to report the problem! As your experience with Buildroot progresses, you will progressively learn when a full rebuild is really necessary, and you will save more and more time.

One of the most common questions asked by Buildroot users is how to rebuild a given package or how to remove a package without rebuilding everything from scratch. Removing a package is unsupported by Buildroot without rebuilding from scratch. Buildroot will then re-extract, re-configure, re-compile and re-install this package from scratch.

It will restart the compilation and installation of the package, but not from scratch: it basically re-executes make and make install inside the package, so it will only rebuild files that changed.

It will restart the configuration, compilation and installation of the package. If re-creating the root filesystem in necessary, one should in addition run make or make all. Internally, Buildroot creates so-called stamp files to keep track of which build steps have been completed for each package. The commands detailed above simply manipulate these stamp files to force Buildroot to restart a specific set of steps of a package build process.

Further details about package special make targets are explained in Section 8. If you intend to do an offline build and just want to download all sources that you previously selected in the configurator menuconfig , nconfig , xconfig or gconfig , then issue:.

You can now disconnect or copy the content of your dl directory to the build-host. As default, everything built by Buildroot is stored in the directory output in the Buildroot tree. Buildroot also supports building out of tree with a syntax similar to the Linux kernel.

If the O path does not exist, Buildroot will create it. When using out-of-tree builds, the Buildroot. config and temporary files are also stored in the output directory. This means that you can safely run multiple builds in parallel using the same source tree as long as they use unique output directories.

Buildroot also honors some environment variables, when they are passed to make or set in the environment:. Filesystem images can get pretty big, depending on the filesystem you choose, the number of packages, whether you provisioned free space… Yet, some locations in the filesystems images may just be empty e. a long run of zeroes ; such a file is called a sparse file.

Most tools can handle sparse files efficiently, and will only store or write those parts of a sparse file that are not empty. tar accepts the -S option to tell it to only store non-zero blocks of sparse files:. You can use sparse files if you need to store the filesystem images e. to transfer from one machine to another , or if you need to send them e. Note however that flashing a filesystem image to a device while using the sparse mode of dd may result in a broken filesystem e.

the block bitmap of an ext2 filesystem may be corrupted; or, if you have sparse files in your filesystem, those parts may not be all-zeroes when read back. You should only use sparse files when handling files on the build machine, not when transferring them to an actual device that will be used on the target. Buildroot can produce a JSON blurb that describes the set of enabled packages in the current configuration, together with their dependencies, licenses and other metadata.

This JSON blurb is produced by using the show-info make target:. Buildroot can also produce details about packages as HTML and JSON output using the pkg-stats make target. Amongst other things, these details include whether known CVEs security vulnerabilities affect the packages in your current configuration. It also shows if there is a newer upstream version for those packages. These dependencies can sometimes be quite complicated, and for a given system, it is often not easy to understand why such or such package was brought into the build by Buildroot.

In order to help understanding the dependencies, and therefore better understand what is the role of the different components in your embedded Linux system, Buildroot is capable of generating dependency graphs. If your system is quite large, the dependency graph may be too complex and difficult to read. It is therefore possible to generate the dependency graph just for a given package:. Note that the dependency graphs are generated using the dot tool from the Graphviz project, which you must have installed on your system to use this feature.

In most distributions, it is available as the graphviz package. By default, the dependency graphs are generated in the PDF format. All formats supported by the -T option of the dot tool are supported. The accepted options are:. When the build of a system takes a long time, it is sometimes useful to be able to understand which packages are the longest to build, to see if anything can be done to speed up the build.

In order to help such build time analysis, Buildroot collects the build time of each step of each package, and allows to generate graphs from this data. The only other format supported is PNG:. When your target system grows, it is sometimes useful to understand how much each Buildroot package is contributing to the overall root filesystem size.

To help with such an analysis, Buildroot collects data about files installed by each package and using this data, generates a graph and CSV files detailing the size contribution of the different packages. Accepted options are:. The collected filesystem size data is only meaningful after a complete clean rebuild. Be sure to run make clean all before using make graph-size. To compare the root filesystem size of two different Buildroot compilations, for example after adjusting the configuration or when switching to another Buildroot release, use the size-stats-compare script.

It takes two file-size-stats. csv files produced by make graph-size as input. Refer to the help text of this script for more details:. This section deals with a very experimental feature, which is known to break even in some non-unusual situations. Use at your own risk. Buildroot has always been capable of using parallel build on a per package basis: each package is built by Buildroot using make -jN or the equivalent invocation for non-make-based build systems. Until As of This feature is however marked as experimental and is known not to work in some cases.

You may want to compile, for your target, your own programs or other software that are not packaged in Buildroot. In order to do this you can use the toolchain that was generated by Buildroot. Alternatively, Buildroot can also export the toolchain and the development files of all selected packages, as an SDK, by running the command make sdk. This tarball can then be distributed to application developers, when they want to develop their applications that are not yet packaged as a Buildroot package.

Upon extracting the SDK tarball, the user must run the script relocate-sdk. sh located at the top directory of the SDK , to make sure all paths are updated with the new location. Alternatively, if you just want to prepare the SDK without generating the tarball e.

because you will just be moving the host directory, or will be generating the tarball on your own , Buildroot also allows you to just prepare the SDK with make prepare-sdk without actually generating a tarball. This script can be sourced with. It also provides some useful commands. Note however that once this script is sourced, the environment is setup only for cross-compilation, and no longer for native compilation.

Buildroot allows to do cross-debugging, where the debugger runs on the build machine and communicates with gdbserver on the target to control the execution of the program.

Now, to start debugging a program called foo , you should run on the target:. This will cause gdbserver to listen on TCP port for a connection from the cross gdb. Of course, foo must be available in the current directory, built with debugging symbols. ccache is a compiler cache.

It stores the object files resulting from each compilation process, and is able to skip future compilation of the same source file with same compiler and same arguments by using the pre-existing object files.

When doing almost identical builds from scratch a number of times, it can nicely speed up the build process. ccache support is integrated in Buildroot. You just have to enable Enable compiler cache in Build options. This will automatically build ccache and use it for every host and target compilation. This default location is outside of Buildroot output directory so that it can be shared by separate Buildroot builds. If you want to get rid of the cache, simply remove this directory.

You can get statistics on the cache its size, number of hits, misses, etc. by running make ccache-stats. For example. ccache makes a hash of the source files and of the compiler options.

If a compiler option is different, the cached object file will not be used. Many compiler options, however, contain an absolute path to the staging directory. Because of this, building in a different output directory would lead to many cache misses.

This will rewrite all absolute paths that point inside the output directory into relative paths. Thus, changing the output directory no longer leads to cache misses. A disadvantage of the relative paths is that they also end up to be relative paths in the object file. Therefore, for example, the debugger will no longer find the file, unless you cd to the output directory first.

If you want to keep a complete version of Buildroot which is known to be working with the associated tarballs, you can make a copy of this directory. This will allow you to regenerate the toolchain and the target filesystem with exactly the same versions. If you maintain several Buildroot trees, it might be better to have a shared download location. The download location can also be set in the.

Unlike most options in the. For packages relying on the Buildroot infrastructure, there are numerous special make targets that can be called independently like this:. target package: Run the installation of the package in the staging directory, if necessary.

target package: Run the installation of the package in the target directory, if necessary. target package: Run the 2 previous installation commands. host package: Run the installation of the package in the host directory. Displays the first-order reverse dependencies of the package i.

e packages that directly depend on it. Recursively displays the reverse dependencies of the package i. e the packages that depend on it, directly or indirectly. Generate a dependency graph of the package, in the context of the current Buildroot configuration. See this section for more details about dependency graphs.

Generate a graph of this package reverse dependencies i. The normal operation of Buildroot is to download a tarball, extract it, configure, compile and install the software component found inside this tarball.

Even when a Git or Subversion repository is used as the input for the package source code, Buildroot creates a tarball out of it, and then behaves as it normally does with tarballs. This behavior is well-suited when Buildroot is used mainly as an integration tool, to build and integrate all the components of an embedded Linux system.

However, if one uses Buildroot during the development of certain components of the system, this behavior is not very convenient: one would instead like to make a small change to the source code of one package, and be able to quickly rebuild the system with Buildroot. Buildroot reads an override file, which allows the user to tell Buildroot the location of the source for certain packages. config file, so local. mk by default lives side-by-side with the.

config file, which means:. In this override file, Buildroot expects to find lines of the form:. Instead, it will directly use the source code available in the specified directory and make clean will not touch this directory. This allows to point Buildroot to your own directories, that can be managed by Git, Subversion, or any other version control system. Source trees for big projects often contain hundreds or thousands of files which are not needed for building, but will slow down the process of copying the sources with rsync.

For example, when working on the webkitgtk package, the following will exclude the tests and in-tree builds from a local WebKit source tree:. By default, Buildroot skips syncing of VCS artifacts e. git and. svn directories. Some packages prefer to have these VCS directories available during build, for example for automatically determining a precise commit reference for version information. To undo this built-in filtering at a cost of a slower speed, add these directories back:.

An important note regarding such project-specific customizations: please carefully consider which changes are indeed project-specific and which changes are also useful to developers outside your project. The Buildroot community highly recommends and encourages the upstreaming of improvements, packages and board support to the official Buildroot project.

Of course, it is sometimes not possible or desirable to upstream because the changes are highly specific or proprietary. This chapter describes how to make such project-specific customizations in Buildroot and how to store them in a way that you can build the same image in a reproducible way, even after running make clean.

By following the recommended strategy, you can even use the same Buildroot tree to build multiple distinct projects! When customizing Buildroot for your project, you will be creating one or more project-specific files that need to be stored somewhere. While most of these files could be placed in any location as their path is to be specified in the Buildroot configuration, the Buildroot developers recommend a specific directory structure which is described in this section.

Orthogonal to this directory structure, you can choose where you place this structure itself: either inside the Buildroot tree, or outside of it using a br2-external tree. Both options are valid, the choice is up to you. It is quite common for a user to have several related projects that partly need the same customizations.

Instead of duplicating these customizations for each project, it is recommended to use a layered customization approach, as explained in this section. Almost all of the customization methods available in Buildroot, like post-build scripts and root filesystem overlays, accept a space-separated list of items. The specified items are always treated in order, from left to right. By creating more than one such item, one for the common customizations and another one for the really project-specific customizations, you can avoid unnecessary duplication.

Depending on your projects, you could even introduce more than two layers. An example directory structure for where a user has two customization layers common and fooboard is:. then first the patches from the common layer would be applied, followed by the patches from the fooboard layer. As already briefly mentioned in Section 9. It can be passed to any Buildroot make invocation. It is automatically saved in the hidden.

mk file in the output directory. It can however be changed at any time by passing a new value, and can be removed by passing an empty value. The path to a br2-external tree can be either absolute or relative. If it is passed as a relative path, it is important to note that it is interpreted relative to the main Buildroot source directory, not to the Buildroot output directory. Note: If using an br2-external tree from before Buildroot See Section A br2-external tree must contain at least those three files, described in the following chapters:.

They are described in the following chapters as well. That file describes the br2-external tree: the name and description for that br2-external tree. The format for this file is line based, with each line starting by a keyword, followed by a colon and one or more spaces, followed by the value assigned to that keyword. There are two keywords currently recognised:.

name , mandatory, defines the name for that br2-external tree. This variable is available both in Kconfig, so you can use it to source your Kconfig files see below and in the Makefile, so that you can use it to include other Makefiles see below or refer to other files like data files from your br2-external tree. Note: Since it is possible to use multiple br2-external trees at once, this name is used by Buildroot to generate variables for each of those trees.

That name is used to identify your br2-external tree, so try to come up with a name that really describes your br2-external tree, in order for it to be relatively unique, so that it does not clash with another name from another br2-external tree, especially if you are planning on somehow sharing your br2-external tree with third parties or using br2-external trees from third parties.

They are also exported in the environment so are available in post-build, post-image and in-fakeroot scripts. Those files which may each be empty can be used to define package recipes i. mk like for packages bundled in Buildroot itself or other custom configuration options or make logic.

Buildroot automatically includes the Config. in from each br2-external tree to make it appear in the top-level configuration menu, and includes the external.

mk from each br2-external tree with the rest of the makefile logic. The main usage of this is to store package recipes. The recommended way to do this is to write a Config. in file that looks like:. You can also define custom configuration options in Config.

in and custom make logic in external. One can store Buildroot defconfigs in the configs subdirectory of the br2-external tree. They will be visible in the make list-defconfigs output, below an External configs label that contains the name of the br2-external tree they are defined in. Note: If a defconfig file is present in more than one br2-external tree, then the one from the last br2-external tree is used. It is thus possible to override a defconfig bundled in Buildroot or another br2-external tree.

For some packages, Buildroot provides a choice between two or more implementations of API-compatible such packages. For example, there is a choice to choose either libjpeg ot jpeg-turbo; there is one between openssl or libressl; there is one to select one of the known, pre-configured toolchains…. It is possible for a br2-external to extend those choices, by providing a set of files that define those alternatives:.

For example, you could set the paths to a global patch directory, to a rootfs overlay and to the kernel configuration file as follows e. by running make menuconfig and filling in these options :. Additional Linux kernel extensions see Section Here is an example layout using all features of br2-external the sample content is shown for the file above it, when it is relevant to explain the br2-external tree; this is all entirely made up just for the sake of illustration, of course :.

desc :. options will not appear in the Toolchain menu. in and will thus appear in the External options menu. The Buildroot configuration can be stored using the command make savedefconfig. This strips the Buildroot configuration down by removing configuration options that are at their default value.

The result is stored in a file called defconfig. The configuration files for BusyBox, the Linux kernel, Barebox, U-Boot and uClibc should be stored as well if changed. For each of these components, a Buildroot configuration option exists to point to an input configuration file, e.

To store their configuration, set these configuration options to a path where you want to save the configuration files, and then use the helper targets described below to actually store the configuration. As explained in Section 9. You can create the configuration file by running make linux-menuconfig etc.

The two recommended methods, which can co-exist, are root filesystem overlay s and post build script s. A filesystem overlay is a tree of files that is copied directly over the target filesystem after it has been built.

You can even specify multiple overlays, space-separated. If you specify a relative path, it will be relative to the root of the Buildroot tree. Hidden directories of version control systems, like. git ,. svn ,. hg , etc. empty and files ending in ~ are excluded from the copy.

As shown in Section 9. Post-build scripts are shell scripts called after Buildroot builds all the selected software, but before the rootfs images are assembled. Using post-build scripts, you can remove or modify any file in your target filesystem. You should, however, use this feature with care. Whenever you find that a certain package generates wrong or unneeded files, you should fix that package rather than work around it with some post-build cleanup scripts.

The post-build scripts are run with the main Buildroot tree as current working directory. The path to the target filesystem is passed as the first argument to each script. All the scripts will be passed the exact same set of arguments, it is not possible to pass different sets of arguments to each script. Below three more methods of customizing the target filesystem are described, but they are not recommended. For temporary modifications, you can modify the target filesystem directly and rebuild the image.

After making your changes, run make to rebuild the target filesystem image. This method allows you to do anything to the target filesystem, but if you need to clean your Buildroot tree using make clean , these changes will be lost. Such cleaning is necessary in several cases, refer to Section 8.

This solution is therefore only useful for quick tests: changes do not survive the make clean command. Once you have validated your changes, you should make sure that they will persist after a make clean , using a root filesystem overlay or a post-build script. The root filesystem image is created from a target skeleton, on top of which all packages install their files.

The default target skeleton provides the standard Unix filesystem layout and some basic init scripts and configuration files. However, if the default skeleton is entirely different than what you need, using a custom skeleton may be more suitable. Both options are available in the System configuration menu. This method is not recommended because it duplicates the entire skeleton, which prevents taking advantage of the fixes or improvements brought to the default skeleton in later Buildroot releases.

This is not a complete substitute for actually being root, but is enough for what Buildroot needs. Post-fakeroot scripts are shell scripts that are called at the end of the fakeroot phase, right before the filesystem image generator is called. As such, they are called in the fakeroot context. Post-fakeroot scripts can be useful in case you need to tweak the filesystem to do modifications that are usually only available to the root user. Note: The difference between post-build scripts above and fakeroot scripts, is that post-build scripts are not called in the fakeroot context.

Note: Using fakeroot is not an absolute substitute for actually being root. Sometimes it is needed to set specific permissions or ownership on files or device nodes. For example, certain files may need to be owned by root.

Since the post-build scripts are not run as root, you cannot do such changes from there unless you use an explicit fakeroot from the post-build script. Instead, Buildroot provides support for so-called permission tables. If you are using a static device table i.

not using devtmpfs , mdev , or e udev then you can add device nodes using the same syntax, in so-called device tables. mk file instead see Section Sometimes it is needed to add specific users in the target system. To cover this requirement, Buildroot provides support for so-called users tables. While post-build scripts Section 9. Post-image scripts can for example be used to automatically extract your root filesystem tarball in a location exported by your NFS server, or to create a special firmware image that bundles your root filesystem and kernel image, or any other custom action required for your project.

Just like post-build scripts, post-image scripts are run with the main Buildroot tree as current working directory. The path to the images output directory is passed as the first argument to each script. The post-image scripts will be executed as the user that executes Buildroot, which should normally not be the root user.

Therefore, any action requiring root permissions in one of these scripts will require special handling usage of fakeroot or sudo , which is left to the script developer.

It is sometimes useful to apply extra patches to packages - on top of those provided in Buildroot. This might be used to support custom features in a project, for example, or when working on a new architecture. For information about how patches are applied for a package, see Section It can be used to specify a patch directory for any package in buildroot. It should also be used in place of the custom patch directory options that are available for packages such as U-Boot and Barebox.

By doing this, it will allow a user to manage their patches from one top-level directory. In general, any new package should be added directly in the package directory and submitted to the Buildroot upstream project. How to add packages to Buildroot in general is explained in full detail in Chapter 18, Adding new packages to Buildroot and will not be repeated here. However, your project may need some proprietary packages that cannot be upstreamed.

This section will explain how you can keep such project-specific packages in a project-specific directory. If you are using the br2-external tree feature see Section 9. However, Buildroot will not be aware of the packages in this location, unless we perform some additional steps.

As explained in Chapter 18, Adding new packages to Buildroot , a package in Buildroot basically consists of two files: a. mk file describing how to build the package and a Config. in file describing the configuration options for this package. Buildroot will automatically include the. If we want Buildroot to include. mk file in a first-level subdirectory that includes these additional. mk files. For the Config. in that includes the Config.

in files of all your packages. An exhaustive list has to be provided since wildcards are not supported in the source command of kconfig. For example:. in , preferably in a company-specific menu to make merges with future Buildroot versions easier.

If using a br2-external tree, refer to Section 9. Earlier in this chapter, the different methods for making project-specific customizations have been described.

This section will now summarize all this by providing step-by-step instructions to storing your project-specific customizations. Clearly, the steps that are not relevant to your project can be skipped. config as far as they are relevant :. This chapter discusses how various things are integrated at system level. Buildroot is highly configurable, almost everything discussed here can be changed or overridden by rootfs overlay or custom skeleton configuration.

Systemd requires a DBus daemon. At least one of them must be chosen. If both are included in the configuration, dbus-broker will be used as system bus, but the traditional dbus-daemon is still installed as well and can be used as session bus. Also its tools e.

dbus-send can be used systemd itself has busctl as an alternative. In addition, the traditional dbus package is the only one that provides libdbus , which is used by many packages as dbus integration library. Both in the dbus and in the dbus-broker case, the daemon runs as user dbus. The DBus configuration files are also identical for both.

To make sure that only one of the two daemons is started as system bus, the systemd activation files of the dbus package dbus. socket and the dbus. service symlink in multi-user. wants are removed when dbus-broker is selected. SELinux is a Linux kernel security module enforcing access control policies. In addition to the traditional file permissions and access control lists, SELinux allows to write rules for users or processes to access specific functions of resources files, sockets….

To have proper support for SELinux in a Buildroot generated system, the following configuration options must be enabled:. The SELinux refpolicy contains modules that can be enabled or disabled when being built.

Each module provide a number of SELinux rules. In Buildroot the non-base modules are disabled by default and several ways to enable such modules are provided:. Buildroot also allows to completely override the refpolicy. This allows to provide a full custom policy designed specifically for a given system. When going this way, all of the above mechanisms are disabled: no extra SElinux module is added to the policy, and all the available modules within the custom policy are enabled and built into the final binary policy.

The custom policy must be a fork of the official refpolicy. In order to fully override the refpolicy the following configuration variables have to be set:. If the boot process seems to hang after the following messages messages not necessarily exactly similar, depending on the list of packages selected :. In order to have the system start a shell on your serial console, you have to go into the Buildroot configuration, in System configuration , modify Run a getty login prompt after boot and set the appropriate port and baud rate in the getty options submenu.

It has been decided that support for the native compiler on the target would be stopped from the Buildroot If you need a compiler on your target anyway, then Buildroot is not suitable for your purpose. In such case, you need a real distribution and you should opt for something like:. Since there is no compiler available on the target see Section Because Buildroot mostly targets small or very small target hardware with limited resource onboard CPU, ram, mass-storage , it does not make sense to waste space with the documentation data.

If you need documentation data on your target anyway, then Buildroot is not suitable for your purpose, and you should look for a real distribution see: Section To know more about the dependencies of a package, search for the package symbol in the config menu see Section 8.

Then, you may have to recursively enable several options which correspond to the unmet dependencies to finally be able to select the package. If the package is not visible due to some unmet toolchain options, then you should certainly run a full rebuild see Section 8.

There are plenty of reasons to not use the target directory a chroot one, among these:. For these reasons, commands run through chroot, using the target directory as the new root, will most likely fail. One feature that is often discussed on the Buildroot list is the general topic of "package management". To summarize, the idea would be to add some tracking of which Buildroot package installs what files, with the goals of:. In general, most people think it is easy to do: just track which package installed what and remove it when the package is unselected.

However, it is much more complicated than that:. For all these reasons, the conclusion is that adding tracking of installed files to remove them when the package is unselected, or to generate a repository of binary packages, is something that is very hard to achieve reliably and will add a lot of complexity. Since Buildroot often involves doing full rebuilds of the entire system that can be quite long, we provide below a number of tips to help reduce the build time:.

All of the end products of Buildroot toolchain, root filesystem, kernel, bootloaders contain open source software, released under various licenses. Using open source software gives you the freedom to build rich embedded systems, choosing from a wide range of packages, but also imposes some obligations that you must know and honour. Some licenses require you to publish the license text in the documentation of your product.

Others require you to redistribute the source code of the software to those that receive your product. The exact requirements of each license are documented in each package, and it is your responsibility or that of your legal office to comply with those requirements.

To make this easier for you, Buildroot can collect for you some material you will probably need. To produce this material, after you have configured Buildroot with make menuconfig , make xconfig or make gconfig , run:. There you will find:.

Please note that the aim of the legal-info feature of Buildroot is to produce all the material that is somehow relevant for legal compliance with the package licenses. Buildroot does not try to produce the exact material that you must somehow make public. Certainly, more material is produced than is needed for a strict legal compliance.

For example, it produces the source code for packages released under BSD-like licenses, that you are not required to redistribute in source form. Moreover, due to technical limitations, Buildroot does not produce some material that you will or may need, such as the toolchain source code for some of the external toolchains and the Buildroot source code itself.

When you run make legal-info , Buildroot produces warnings in the README file to inform you of relevant material that could not be saved. Finally, keep in mind that the output of make legal-info is based on declarative statements in each of the packages recipes. The Buildroot developers try to do their best to keep those declarative statements as accurate as possible, to the best of their knowledge. However, it is very well possible that those declarative statements are not all fully accurate nor exhaustive.

You or your legal department have to check the output of make legal-info before using it as your own compliance delivery. See the NO WARRANTY clauses clauses 11 and 12 in the COPYING file at the root of the Buildroot distribution.

Buildroot itself is an open source software, released under the GNU General Public License, version 2 or at your option any later version, with the exception of the package patches detailed below.

However, being a build system, it is not normally part of the end product: if you develop the root filesystem, kernel, bootloader or toolchain for a device, the code of Buildroot is only present on the development machine, not in the device storage. Nevertheless, the general view of the Buildroot developers is that you should release the Buildroot source code along with the source code of other packages when releasing a product that contains GPL-licensed software.

This is because the GNU GPL defines the " complete source code " for an executable work as " all the source code for all modules it contains, plus any associated interface definition files, plus the scripts used to control compilation and installation of the executable ".

Buildroot is part of the scripts used to control compilation and installation of the executable , and as such it is considered part of the material that must be redistributed. Keep in mind that this is only the Buildroot developers' opinion, and you should consult your legal department or lawyer in case of any doubt. Buildroot also bundles patch files, which are applied to the sources of the various packages. Those patches are not covered by the license of Buildroot.

Instead, they are covered by the license of the software to which the patches are applied. When said software is available under multiple licenses, the Buildroot patches are only provided under the publicly accessible licenses. See Chapter 19, Patching a package for the technical details. To achieve NFS-boot, enable tar root filesystem in the Filesystem images menu.

To build a live CD image, enable the iso image option in the Filesystem images menu. Note that this option is only available on the x86 and x architectures, and if you are building your kernel with Buildroot.

You can build a live CD image with either IsoLinux, Grub or Grub 2 as a bootloader, but only Isolinux supports making this image usable both as a live CD and live USB through the Build hybrid image option.

As mentioned above, Buildroot is basically a set of Makefiles that download, configure, and compile software with the correct options. It also includes patches for various software packages - mainly the ones involved in the cross-compilation toolchain gcc , binutils and uClibc. There is basically one Makefile per software package, and they are named with the. mk extension. Makefiles are split into many different parts.

Overall, these coding style rules are here to help you to add new files in Buildroot or refactor existing ones. If you slightly modify some existing file, the important thing is to keep the consistency of the whole file, so you can:.

in files contain entries for almost anything configurable in Buildroot. The Config. in files are the input for the configuration tool used in Buildroot, which is the regular Kconfig.

Header: The file starts with a header. It contains the module name, preferably in lowercase, enclosed between separators made of 80 hashes. A blank line is mandatory after the header:. Note that commands inside a define block should always start with a tab, so make recognizes them as commands. cfg files contain the output image layout that genimage utility uses to create final.

img file. The genimage. cfg files are the input for the genimage tool used in Buildroot to generate the final image file i. The documentation uses the asciidoc format. Buildroot contains basic configurations for several publicly available hardware boards, so that users of such a board can easily build a system that is known to work.

You are welcome to add support for other boards to Buildroot too. To do so, you need to create a normal Buildroot configuration that builds a basic system for the hardware: internal toolchain, kernel, bootloader, filesystem and a simple BusyBox-only userspace. No specific package should be selected: the configuration should be as minimal as possible, and should only build a working basic BusyBox system for the target platform.

You can of course use more complicated configurations for your internal projects, but the Buildroot project will only integrate basic board configurations. This is because package selections are highly application-specific. Once you have a known working configuration, run make savedefconfig. This will generate a minimal defconfig file at the root of the Buildroot source tree.

If the configuration is a bit more complicated, it is nice to manually reformat it and separate it into sections, with a comment before each section. Typical sections are Architecture , Toolchain options typically just linux headers version , Firmware , Bootloader , Kernel , and Filesystem.

Always use fixed versions or commit hashes for the different components, not the "latest" version. It is recommended to use as much as possible upstream versions of the Linux kernel and bootloaders, and to use as much as possible default kernel and bootloader configurations.

If they are incorrect for your board, or no default exists, we encourage you to send fixes to the corresponding upstream projects. However, in the mean time, you may want to store kernel or bootloader configuration or patches specific to your target platform.

You can then store your patches and configurations in these directories, and reference them from the main Buildroot configuration. Refer to Chapter 9, Project-specific customization for more details. Before submitting patches for new boards it is recommended to test it by building it using latest gitlab-CI docker container. This section covers how new packages userspace libraries or applications can be integrated into Buildroot.

It also shows how existing packages are integrated, which is needed for fixing issues or tuning their configuration. When you add a new package, be sure to test it in various conditions see Section First of all, create a directory under the package directory for your software, for example libfoo. Some packages have been grouped by topic in a sub-directory: x11r7 , qt5 and gstreamer. If your package fits in one of these categories, then create your package directory in these.

New subdirectories are discouraged, however. For the package to be displayed in the configuration tool, you need to create a Config file in your package directory. There are two types: Config. in and Config. For packages used on the target, create a file named Config. This file will contain the option descriptions related to our libfoo software that will be used and displayed in the configuration tool.

It should basically contain:. The bool line, help line and other metadata information about the configuration option must be indented with one tab. The help text itself should be indented with one tab and two spaces, lines should be wrapped to fit 72 columns, where tab counts for 8, so 62 characters in the text itself. The help text must mention the upstream URL of the project after an empty line. You can look at examples in other packages. The syntax of the Config. in file is the same as the one for the kernel Kconfig file.

in or in a category subdirectory if you decided to put your package in one of the existing categories. The files included there are sorted alphabetically per category and are NOT supposed to contain anything but the bare name of the package. The host package should be explicitly selectable by the user from the configuration menu.

In this case, create a Config. host file for that host package:. The same coding style and options as for the Config. in file are valid. The files included there are sorted alphabetically and are NOT supposed to contain anything but the bare name of the package. The host package will then be available from the Host utilities menu. in file of your package must also ensure that dependencies are enabled. Typically, Buildroot uses the following rules:.

The current problem with the kconfig language is that these two dependency semantics are not internally linked. An example illustrates both the usage of select and depends on. Overall, for package library dependencies, select should be preferred.

Note that such dependencies will ensure that the dependency option is also enabled, but not necessarily built before your package. To do so, the dependency also needs to be expressed in the. mk file of the package. Further formatting details: see the coding style. Some packages can only be built on certain target architectures, or if an MMU is available in the processor.

These dependencies have to be expressed with the appropriate depends on statements in the Config. in file. Additionally, for dependencies on toolchain options, a comment should be displayed when the option is not enabled, so that the user knows why the package is not available.

Dependencies on target architecture or MMU support should not be made visible in a comment: since it is unlikely that the user can freely choose another target, it makes little sense to show these dependencies explicitly. The comment should only be visible if the config option itself would be visible when the toolchain option dependencies are met. This means that all other dependencies of the package including dependencies on target architecture and MMU support have to be repeated on the comment definition.

To keep it clear, the depends on statement for these non-toolchain option should be kept separate from the depends on statement for the toolchain options.

If there is a dependency on a config option in that same file typically the main package it is preferable to have a global if … endif construct rather than repeating the depends on statement on the comment and other config options. The rest of this section enumerates the different target and toolchain options, the corresponding config symbols to depend on, and the text to use in the comment.

They are available in variants operating on 1 byte, 2 bytes, 4 bytes and 8 bytes. Since different architectures support atomic operations on different sizes, one dependency symbol is available for each size:. Some packages need a Linux kernel to be built by buildroot. These are typically kernel modules or firmware. A comment should be added in the Config. in file to express this dependency, similar to dependencies on toolchain options.

The general format is:. Create a file named libfoo. It describes how the package should be downloaded, configured, built, installed, etc. Depending on the package type, the. mk file must be written in a different way, using different infrastructures:.

Further formatting details: see the writing rules. When possible, you must add a third file, named libfoo. hash , that contains the hashes of the downloaded files for the libfoo package. The only reason for not adding a. hash file is when hash checking is not possible due to how the package is downloaded.

When a package has a version selection choice, then the hash file may be stored in a subdirectory named after the version, e. This is especially important if the different versions have different licensing terms, but they are stored in the same file. The hashes stored in that file are used to validate the integrity of the downloaded files and of the license files.

Why, ones like the "agreement between Activision Blizzard and Sony," that places "restrictions on the ability of Activision Blizzard to place COD titles on Game Pass for a number of years". It was apparently these kinds of agreements that Xbox's Phil Spencer had in mind opens in new tab when he spoke to Sony bosses in January and confirmed Microsoft's "intent to honor all existing agreements upon acquisition of Activision Blizzard".

Unfortunately, the footnote ends there, so there's not much in the way of detail about what these restrictions are or how long they'd remain in effect in a potential post-acquisition world.

Given COD's continued non-appearance on Game Pass, you've got to imagine the restrictions are fairly significant if they're not an outright block on COD coming to the service. Either way, the simple fact that Microsoft is apparently willing to maintain any restrictions on its own ability to put first-party games on Game Pass is rather remarkable, given that making Game Pass more appealing is one of the reasons for its acquisition spree.

The irony of Sony making deals like this one while fretting about COD's future on PlayStation probably isn't lost on Microsoft's lawyers, which is no doubt part of why they brought it up to the CMA. While it's absolutely reasonable to worry about a world in which more and more properties are concentrated in the hands of singular, giant megacorps, it does look a bit odd if you're complaining about losing access to games while stopping them from joining competing services.

We'll find out if the CMA agrees when it completes its in-depth, "Phase 2" investigation opens in new tab into the Activision Blizzard acquisition, which is some way off yet. For now, we'll have to content ourselves with poring over these kinds of corporate submissions for more interesting tidbits like this one.

So far, we've already learned that Microsoft privately has a gloomy forecast for the future of cloud gaming opens in new tab , and that the company thinks Sony shouldn't worry so much since, hey, future COD games might be as underwhelming as Vanguard opens in new tab. Who knows what we'll learn next? Sign up to get the best content of the week, and great gaming deals, as picked by the editors. One of Josh's first memories is of playing Quake 2 on the family computer when he was much too young to be doing that, and he's been irreparably game-brained ever since.

His writing has been featured in Vice, Fanbyte, and the Financial Times. He'll play pretty much anything, and has written far too much on everything from visual novels to Assassin's Creed.

A footnote in Microsoft's submission opens in new tab to the UK's Competition and Markets Authority CMA has let slip the reason behind Call of Duty's absence from the Xbox Game Pass library: Sony and Activision Blizzard have a deal that restricts the games' presence on the service.

The footnote appears in a section detailing the potential benefits to consumers from Microsoft's point of view of the Activision Blizzard catalogue coming to Game Pass.

What existing contractual obligations are those? Why, ones like the "agreement between Activision Blizzard and Sony," that places "restrictions on the ability of Activision Blizzard to place COD titles on Game Pass for a number of years". It was apparently these kinds of agreements that Xbox's Phil Spencer had in mind opens in new tab when he spoke to Sony bosses in January and confirmed Microsoft's "intent to honor all existing agreements upon acquisition of Activision Blizzard".

Unfortunately, the footnote ends there, so there's not much in the way of detail about what these restrictions are or how long they'd remain in effect in a potential post-acquisition world. Given COD's continued non-appearance on Game Pass, you've got to imagine the restrictions are fairly significant if they're not an outright block on COD coming to the service.

Either way, the simple fact that Microsoft is apparently willing to maintain any restrictions on its own ability to put first-party games on Game Pass is rather remarkable, given that making Game Pass more appealing is one of the reasons for its acquisition spree. The irony of Sony making deals like this one while fretting about COD's future on PlayStation probably isn't lost on Microsoft's lawyers, which is no doubt part of why they brought it up to the CMA.

While it's absolutely reasonable to worry about a world in which more and more properties are concentrated in the hands of singular, giant megacorps, it does look a bit odd if you're complaining about losing access to games while stopping them from joining competing services. We'll find out if the CMA agrees when it completes its in-depth, "Phase 2" investigation opens in new tab into the Activision Blizzard acquisition, which is some way off yet.

For now, we'll have to content ourselves with poring over these kinds of corporate submissions for more interesting tidbits like this one. So far, we've already learned that Microsoft privately has a gloomy forecast for the future of cloud gaming opens in new tab , and that the company thinks Sony shouldn't worry so much since, hey, future COD games might be as underwhelming as Vanguard opens in new tab.

Who knows what we'll learn next? Sign up to get the best content of the week, and great gaming deals, as picked by the editors. One of Josh's first memories is of playing Quake 2 on the family computer when he was much too young to be doing that, and he's been irreparably game-brained ever since.

His writing has been featured in Vice, Fanbyte, and the Financial Times. He'll play pretty much anything, and has written far too much on everything from visual novels to Assassin's Creed. His most profound loves are for CRPGs, immersive sims, and any game whose ambition outstrips its budget.

He thinks you're all far too mean about Deus Ex: Invisible War. Open menu Close menu PC Gamer PC Gamer THE GLOBAL AUTHORITY ON PC GAMES. opens in new tab opens in new tab opens in new tab opens in new tab opens in new tab opens in new tab. US Edition. News Reviews Hardware Best Of Magazine The Top Forum More PCGaming Show Podcasts Coupons Newsletter SignUp Community Guidelines Affiliate Links Meet the team About PC Gamer.

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Use the -f option to download a new version of a snippet or zinit update {URL}. Bitcoin and Ethereum remain the most traded, but you can find brokers that list 50 or more alt coins. These dependencies are listed in terms of lower-case package names, which can be packages for the target without the host- prefix or packages for the host with the host- prefix. This is often needed for libraries, since they must install header files and other development files in the staging space. Instead these toolchains come with a very large set of pre-compiled libraries and programs. It consists of a compiler in our case, gcc , binary utils like assembler and linker in our case, binutils and a C standard library for example GNU Libc , uClibc-ng. Mails that are sent to the mailing list are also available in the mailing list archives, available through Mailman or at lore.

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