Extra: buildroot scripts¶

Buildroot has a series of mechanisms to assist in the customization of the generated image:

• https://buildroot.org/downloads/manual/manual.html#_support_scripts

We will look at two types:

• Using the overlay feature
• Modifying the files before generating the tar fakeroot

overlay¶

It will copy files to the /etc/init.d folder, for this:

• Create a folder called overlay in the root of the buildroot
• Create a new file S41static
• Configure the buildroot:
  • System Configuration -> Root filesystem overlay directories: overlay

#!/bin/sh

case "$1" in
  start)
        start
        ifconfig eth0 up
        ifconfig eth0 169.254.0.13 netmask 255.255.0.0 up
        ;;
  stop)
        stop
        ;;
  restart|reload)
        restart
        ;;
  *)
        echo "Usage: $0 {start|stop|restart}"
        exit 1
esac

Done, now every time we generate a new buildroot it will copy the script to initialize the network.

fakeroot¶

Let's create a script that will be executed before buildroot creates the .tar:

Post-fakeroot scripts (BR2_ROOTFS_POST_FAKEROOT_SCRIPT) When aggregating the final images, some parts of the process require root rights: creating device nodes in /dev, setting permissions or ownership to files and directories… To avoid requiring actual root rights, Buildroot uses fakeroot to simulate root rights. This is not a complete substitute for actually being root, but is enough for what Buildroot needs.

Create a folder in buildroot called custom_script and add two files:

#!/bin/sh

INIT=$1/etc/init.d/
FILE=S41static

echo "--------------------------------"
echo "BUILDROOT SCRIPT"

# static ip
cp custom-scripts/S41staticIp $INIT
chmod +x $INIT/S41staticIp

echo "--------------------------------"

#!/bin/bash

case "$1" in
start)
    printf "Setting ip: "
    /sbin/ifconfig eth0 169.254.0.13 netmask 255.255.0.0 up
    [ $? = 0 ] && echo "OK" || echo "FAIL"
    ;; 
*)
    exit 1
    ;;
esac

Now we need to configure the buildroot to execute script.py, in:

• System configuration/Custom scripts to run inside the fakeroot environment
• custom-scripts/script.sh

Every time the .tar is generated, buildroot will create the network configuration file.