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Setting Up the Cross Compile Environment

Boken Lin edited this page Nov 4, 2015 · 2 revisions

Setting Up Cross-Compile Environment for Omega

Step 1: Setup OpenWRT Buildroot Environment

Install tools and library sources:

$ apt-get install -y subversion build-essential libncurses5-dev zlib1g-dev gawk flex quilt git-core unzip libssl-dev

Step 2: Get OpenWRT Source

$ git clone git://
$ cd openwrt

Step 3: Update Feeds

Feeds are repositories of packages that can be added to the OpenWRT system. Feeds are configured in the feeds.conf.default file. Additional feeds can be added by editing this file. For example, to add the Onion packages, append the following line to the file:

src-git onion

Save the feeds.conf.default file, and update the feeds:

$ scripts/feeds update -a

This will fetch all the repositories configured in the feeds.conf.default file.

To install a package to the source we are about to compile, for example:

$ scripts/feeds install python

This downloads python to our source code tree, but doesn't compile the package by default.

Step 4: Modify Image

Files in the package/base-file/files directory will be overwritten to the compiled image at the end of the compilation process. To add custom files to the compiled image, create a files folder in the buildroot directory. Files in this directory will supersede the files in the package/base-file/files directory.

Step 5: Select Packages

As mentioned, packages installed are not selected by default when compiling the image, and will not appear in the final firmware. To select packages to be compiled into the image:

$ make menuconfig

Navigate with UP and DOWN keys. ENTER to enter into a category. To exit to previous menu press ESC twice. To toggle the selection state of packages press SPACE.

First ensure the following:

  • Target System is Atheros AR7xxx/AR9xxx
  • Subtarget is Generic
  • Target Profile is Onion Omega
  • Target Images is squashfs

Different markings on packages represent their selection state. < > are unselected; <*> are selected; <M> are selected to compile as modules (i.e. compiled as Opkg packages, but not included in the image by default); -*- are dependencies required by other package(s).

Selection state can be toggled using SPACE, or N for unselected, Y for selected, and M for module.

When package selection is finished, exit out of menuconfig by pressing ESC twice. When prompted whether to save changes, select Yes.

Step 6a: Compile Image

Start the compile process:

$ make

On multi-core systems, add the -j flag to take advantage of additional cores:

$ make -jn

where n is the number of cores (nproc) + 1.

To enable verbose mode:

$ make V=s

Once the compile is complete, binaries are found in the bin/ar71xx directory. openwrt-ar71xx-generic-onion-omega-squashfs-factory.bin is the full image, and openwrt-ar71xx-generic-onion-omega-squashfs-sysupgrade.bin is the image for system upgrade.

Compiled Opkg packages are found in the bin/ar71xx/packages directory.

Step 6b: Compile Individual Packages

Compiling the entire image can take a long time depending on the system. Luckily, individual packages can be compiled without needing to compile the whole image.

First, we need to build the toolchain to compile and package the binaries (this is typically done by make automatically when building the image, and it only needs to be done once):

$ make tools/install
$ make toolchain/install

Now you can compile the individual package:

$ make package/<package name>/compile

where <package name> needs to be substituted for the package in question. Also note that if this package has dependencies, they must be compiled first using the same command.

Finally, if you decide the newly compiled package should be installed into the image:

$ make package/<package name>/install

will install it into the image that you have already created.

Finally, if you wish to generate the index for the package:

$ make package/index

This is typically done automatically by make to keep an updated list of packages installed in the image.

Step 7: Flash Image

On the Omega, cd to /tmp:

# cd /tmp

This is done because /tmp is a RAM disk that has enough storage to download the image to be flashed.

Download the image:

# wget

Once the image is downloaded, start the flash process:

# sysupgrade openwrt-ar71xx-generic-onion-omega-squashfs-factory.bin

If you wish the system to try to preserve modified files in /etc directory, where most of the configuration is kept, add the -c flag:

# sysupgrade -c openwrt-ar71xx-generic-onion-omega-squashfs-factory.bin

If you wish to overwrite all configuration changes and restore the original image setting, add the -n flag:

# sysupgrade -n openwrt-ar71xx-generic-onion-omega-squashfs-factory.bin