buildroot

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[[customize-store-buildroot-config]]

=== Storing the Buildroot configuration

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The Buildroot configuration can be stored using the command

 +make savedefconfig+.

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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+. If you want to save it in another place, change the

+BR2_DEFCONFIG+ option in the Buildroot configuration itself, or call

make with +make savedefconfig BR2_DEFCONFIG=<path-to-defconfig>+.

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The recommended place to store this defconfig is

+configs/<boardname>_defconfig+. If you follow this recommendation, the

configuration will be listed in +make help+ and can be set again by

running +make <boardname>_defconfig+.

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Alternatively, you can copy the file to any other place and rebuild with

+make defconfig BR2_DEFCONFIG=<path-to-defconfig-file>+.

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[[customize-store-package-config]]

=== Storing the configuration of other components

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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.g. +BR2_LINUX_KERNEL_CUSTOM_CONFIG_FILE+. 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.

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As explained in xref:customize-dir-structure[], the recommended path to

store these configuration files is

+board/<company>/<boardname>/foo.config+.

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Make sure that you create a configuration file 'before' changing

the +BR2_LINUX_KERNEL_CUSTOM_CONFIG_FILE+ etc. options. Otherwise,

Buildroot will try to access this config file, which doesn't exist

yet, and will fail. You can create the configuration file by running

+make linux-menuconfig+ etc.

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Buildroot provides a few helper targets to make the saving of

configuration files easier.

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* +make linux-update-defconfig+ saves the linux configuration to the

  path specified by +BR2_LINUX_KERNEL_CUSTOM_CONFIG_FILE+. It

  simplifies the config file by removing default values. However,

  this only works with kernels starting from 2.6.33. For earlier

  kernels, use +make linux-update-config+.

* +make busybox-update-config+ saves the busybox configuration to the

  path specified by +BR2_PACKAGE_BUSYBOX_CONFIG+.

* +make uclibc-update-config+ saves the uClibc configuration to the

  path specified by +BR2_UCLIBC_CONFIG+.

* +make barebox-update-defconfig+ saves the barebox configuration to the

  path specified by +BR2_TARGET_BAREBOX_CUSTOM_CONFIG_FILE+.

* +make uboot-update-defconfig+ saves the U-Boot configuration to the

  path specified by +BR2_TARGET_UBOOT_CUSTOM_CONFIG_FILE+.

* For at91bootstrap3, no helper exists so you have to copy the config

  file manually to +BR2_TARGET_AT91BOOTSTRAP3_CUSTOM_CONFIG_FILE+.

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