If you already have a BusyBox configuration file, you can directly specify this file in the Buildroot configuration, using BR2_PACKAGE_BUSYBOX_CONFIG. 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 [env-vars] for more details.

Configuration of uClibc is done in the same way as for BusyBox. The configuration variable to specify an existing configuration file is BR2_UCLIBC_CONFIG. The command to make subsequent changes is make uclibc-menuconfig.

If you already have a kernel configuration file, you can directly specify this file in the Buildroot configuration, using BR2_LINUX_KERNEL_USE_CUSTOM_CONFIG.

If you do not yet have a kernel configuration file, you can either start by specifying a defconfig in the Buildroot configuration, using BR2_LINUX_KERNEL_USE_DEFCONFIG, or start by creating an empty file and specifying it as custom configuration file, using BR2_LINUX_KERNEL_USE_CUSTOM_CONFIG.

To make subsequent changes to the configuration, use make linux-menuconfig to open the Linux configuration editor.

Configuration of Barebox is done in the same way as for the Linux kernel. The corresponding configuration variables are BR2_TARGET_BAREBOX_USE_CUSTOM_CONFIG and BR2_TARGET_BAREBOX_USE_DEFCONFIG. To open the configuration editor, use make barebox-menuconfig.

Configuration of U-Boot (version 2015.04 or newer) is done in the same way as for the Linux kernel. The corresponding configuration variables are BR2_TARGET_UBOOT_USE_CUSTOM_CONFIG and BR2_TARGET_UBOOT_USE_DEFCONFIG. To open the configuration editor, use make uboot-menuconfig.