After a few days struggling with rootfs, I tend to use the simplest way – busybox. I got some fails when compiling the buildroot source code. For debugging network code, I think busybox is enough. I don’t want to waste time on building a filesystem.

  • Download BusyBox BusyBox can be downloaded from its git server.

     $ git clone git://busybox.net/busybox.git
 $ git checkout remotes/origin/1_NN_stable

  • Tune BusyBox Setting

     $ make menuconfig  BusyBox Settings --> Build Options -> Build BusyBox as a static binary (no shared libs)  	  BusyBox Settings --> Build Options -> CrossCompiler prefix  Other settings, like networking ......

  • Build BusyBox

     $ make install

  • Update filesystem

     $ cd _install
 $ mkdir proc sys dev etc etc/init.d

  • Create _install/etc/init.d/rcS

     #!/bin/sh
 mount -t proc none /proc
 mount -t sysfs none /sys
 /sbin/mdev -s

  • Then set it as an executable file:

     $ chmod +x _install/etc/init.d/rcS

  • Create image

     $ cd _install
 $ find . | cpio -o --format=newc > ../rootfs.img
 $ cd ..
 $ gzip -c rootfs.img > rootfs.img.gz

  • Boot Linux with initram image

     $ qemu-system-arm -M vexpress-a9 -kernel zImage -initrd rootfs.img -serial stdio -curses -append "console=tty1 root=/dev/ram rdinit=/sbin/init ip=dhcp"

  • Boot Linux with NFS filesystem:

    • Install DHCP server

       $ sudo service nfs-kernel-server start

    • export folder in /etc/exports

       /busybox/_install 127.0.0.1(rw,sync,no_subtree_check,no_root_squash,insecure)

    • Restart NFS server

       $ sudo service nfs-kernel-server restart

    • Then boot Linux:

       $ qemu-system-arm -M vexpress-a9 -kernel zImage -append "console=tty1 root=/dev/nfs nfsroot=10.0.2.2:/busybox/_install rw ip=dhcp init=/sbin/init"