Buildroot: out-of-tree builds

Buildroot: out-of-tree builds

Like the Linux kernel, Buildroot supports building out-of-tree in a very similiar way. This could be very useful when you have multiple configurations in the same Buildroot repository that you want to build without interference.

Consider the following example:

cd buildroot/
mkdir -p ../outputs/device{1,2}

make O=../outputs/device1 menuconfig
make O=../outputs/device1

make O=../outputs/device2 menuconfig
make O=../outputs/device2

Each output has its own .config so you may change the build configurations independently.

The big benefit compared with git worktree [1] or other multiple-instances-of-the-same-repository-approaches is that the dl directory is shared (without need to specify BR2_DL_DIR [2]) among all build directories.

The feature is documented in the Buildroot manual [3].

config utility for Buildroot

config utility for Buildroot

I'm using the ./scripts/config script in the Linux kernel tree a lot. The script is used to manipulate a .config file from the command line which is quite nice to be able to do.

I use it mostly to enable configurations from a script or as a part of automated tests.

Buildroot is also using KBuild as its configuration system so I adapted this script and submitted a patch. It is now part of the mainline.

commit f2c5c7a263d9d61faba80544e0f6ac6da03716ee
Author: Marcus Folkesson <>
Date:   Tue Sep 26 23:15:02 2017 +0200

utils/config: new script to manipulate .config files on the command line

Default prefix is set to `BR2_` but may be overidden by setting

Example usage:

./utils/config --package --enable GNUPG

Check state of config option `BR2_PACKAGE_GNUPG`:
./utils/config --package --state GNUPG

./utils/config --package --disable GNUPG

Set `BR2_TARGET_GENERIC_ISSUE` to "Welcome":
./utils/config --set-str  TARGET_GENERIC_ISSUE "Welcome"

Copied from the Linux kernel (4.13-rc6) source code and adapted to
Thanks to Andi Kleen who is the original author of this script.

Signed-off-by: Marcus Folkesson <>
[Arnout: merge the two tr invications]
Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <>

In addition to all commands found in he Linux kernel version, I also addes the --package config as a shortcut to operate on packages.