I had several experiences with buildroot, it is a "simple" way to build your own embedded operating system.
"Buildroot is a set of Makefiles and patches that makes it easy to generate a complete embedded Linux system. Buildroot can generate any or all of a cross-compilation toolchain, a root filesystem, a kernel image and a bootloader image. Buildroot is useful mainly for people working with small or embedded systems, using various CPU architectures (x86, ARM, MIPS, PowerPC, etc.) : it automates the building process of your embedded system and eases the cross-compilation process."
Anyway, normally, when you have a buildroot system you don't have any of the graphical configuration tools you normally have when you are using your desktop Linux.
So you have to know something about the configuration of a buildroot environment.
Configuring the network interfaces is one of the most important step to use buildroot, because sometimes on the embedded system you don't have display, keyboard or similar input devices, so to use your E.S. you have to use the network.
The configuration shall be done into the file /etc/network/interfaces:
$ cat /etc/network/interfaces
# Configure Loopback
iface lo inet loopback
iface eth0 inet static
# Configure eth0 with dhcp IP
# auto eth0
# iface eth0 inet dhcp
In the above code I've configured the eth0 interface with a static IP address. Normally with buildroot the eth0 is configured to use the dhcp to obtain an IP address (the last two lines do this, I've commented out them).