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Development FAQ

See also the OpenWrt development center website. There you can browse the source code and send reproducible bugs with the ticket system (in trac).

other articles worth reading:

  1. about the Toolchain
  2. about it's installation OpenWrt Buildroot – Installation
  3. about it's usage OpenWrt Buildroot – Usage

Where is the source code?

Almost every software in OpenWrt is available as a package. OpenWrt *downloads* code (using archive, git …) compiles it and includes in the final image. Every archive lands in "dl" directory". Every code (from archive or git) is available in build_dir.

A mirror of package sources is maintained at

How much disk space is needed for compiling ?

Approximately required disc space for compiling OpenWrt:

Branch Min. Max.
typical, Stable 1.5 GB 3.5 GB
Development ? 3.8 GB
Development+feeds ? >5 GB
all feeds/pkgs >30 GB
all feeds+debug FIXME

Typical: Compile an Image that is working on typical consumer routers that have 4MB or 8MB flash.

Compiling also tested on some Windows OS under AndLinux (coLinux + Ubuntu)

What System can I build OpenWrt on ?

OpenWrt Buildroot needs a case sensitive file system.

It should work on almost any Linux Distribution. Tested: Debian (6, 7, Unstable(2014)), Ubuntu, Fedora 19,20 , Arch Linux, OpenSuse 13.3 Exotic Linux variants might have some bugs regarding headers (Alpine Linux). BSD (FreeBSD), MacOSX are somewhat untested. Cygwin (Windows) has possible issues with file system being not case sensitive.

Recommended: Build older versions with older Linux versions in a VM.

How much time is needed for compiling ?

Build-time is highly dependable on the number of Cores/Jobs and can be shrunk to less than 30 minutes (from 90 minutes). Build time with single core can take several hours.

FIXME see Hints to reduce build time

make jobs time needed source
1, typical
1, all 10h48min buildbot
2 all,local feed. mirrots 3h40min
4,typical 45min
4, all,local feed, mirrors 2h17min

Typical: select packages fitting into 8MB flash, build on HDD, ar71xx or brcm47xx target


Yes, of course. If you find any bugs, please use our ticket system or send a report to . You can send patches for the bugs as well.

/!\ NOTE: Changes to the buildroot system or the associated

could break the compile process. Please do not submit bug reports against modified copies of buildroot. Thanks!

How do I create a package?

How can I help or contribute ?




The OpenWrt build bots provide a list of broken packages:

There is a comparison of OpenWrt and upstream package versions available:


The mailing list: generates Patchwork entries:

How can I speed up build process ?

  • Use -j switch to enable parallel builds
  • Use local mirror to avoid downloads (advanced build options)


  • use local feeds ( src-link ) instead of downloading with git

Help me - I build an image and it's too large ! My rootfs is too small! My router does not remember settings!

  • you installed or selected too many packages
  • select packages with "y" / shows as "*" so they get included in squashfs instead of installing them later to jffs2
  • delete unused base packages: :!: be very careful :!:

Example ppp :luci automatically selects ppp. This is not always needed.

  1. de-select "luci"
  2. pick the components manually: luci-base, luci-mod-admin-full, luci-theme-bootstrap
  • use extroot
  • disable busybox features
  • hardware mod your router with larger flash ( :!: possible bootloader modification )

Common errors

Unclean buildroot

- Files inside the buildroot are specific to host systems.

Build dependency: Please install GNU find

# old files in staging_dir/host

- remove untracked files with the help of svn or git

- use make targets depending on what you don't want

make clean
make dirclean
make distclean
make target/linux/clean *
rm -rf tmp/
rm .config .config.old
* Kernel Config change is not triggering rebuild, see: openwrt-devel

If you are running a buildroot inside a VM with many threads you might experience random build failures.

Setup: Host: i7 16GB RAM, VM on Harddisk, Win 7 64bit, VMWare Player Guest: Lubuntu 13.04 64bit 4GB RAM ext4 partition make -j 8

Errors: Build fails like

mv: cannot stat '.deps/dlog.Tpo': No such file or directory


../libtool: line 46: -c: command not found
libtool: Version mismatch error.  This is libtool 2.4, but the
libtool: definition of this LT_INIT comes from libtool 2.2.6.
libtool: You should recreate aclocal.m4 with macros from libtool 2.4
libtool: and run autoconf again.
cleaning up buildroot helps sometimes, reduce concurrency

doc/faq/development.txt · Last modified: 2014/10/26 18:16 by theoradicus