Testing

Integration testing of configuration will be done using a QEMUed jessie raspbian image.

These steps assume you have the necessary tools installed.

Fedora:

$ sudo dnf install qemu-system-arm

Debian/Ubuntu:

$ sudo apt install qemu-system-arm

Building disk image

Building a new disk image to use for testing is currently a manual process. In the future, this could be automated.

  1. Grab a copy of the latest ‘raspbian jessie lite’ image from the raspberry pi website (https://www.raspberrypi.org/downloads/raspbian/). I’m using 2015-11-21-raspbian-jessie-lite.img here.

  2. Use fdisk to find the partition boundaries in this image:

    ~/g/dewi (master) $ fdisk -l 2015-11-21-raspbian-jessie-lite.img
Disk 2015-11-21-raspbian-jessie-lite.img: 1.4 GiB, 1458569216 bytes, 2848768 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: dos
Disk identifier: 0xb3c5e39a

Device                               Boot  Start     End Sectors  Size Id Type
2015-11-21-raspbian-jessie-lite.img1        8192  131071  122880   60M  c W95 FAT32 (LBA)
2015-11-21-raspbian-jessie-lite.img2      131072 2848767 2717696  1.3G 83 Linux

  3. Next, we need to mount that image. To do this, we need to use the information fdisk told us. The start of the main partition is block 131072, and the block size is 512, so the total offset is 131072*512 = 67108864.

    Make a temporary directory to mount the image in:

    $ mkdir raspbian-jessie-mount-point

    and mount the image:

    $ sudo mount -o loop,offset=67108864 2015-11-21-raspbian-jessie-lite.img raspbian-jessie-mount-point

  4. Edit raspbian-jessie-mount-point/etc/ld.so.preload and comment out all lines.

  5. Edit raspbian-jessie-mount-point/etc/fstab and comment out any entry related to mmcblk.

  6. Unmount the image:

    $ sudo umount raspbian-jessie-mount-point

The resulting image can be reduced in size by converting to a sparse file:

$ fallocate -v --dig-holes 2015-11-21-raspbian-jessie-lite.img
2015-11-21-raspbian-jessie-lite.img: 494.7 MiB (518729728 bytes) converted to sparse holes.

Or compressing:

$ xz 2015-11-21-raspbian-jessie-lite.img

Booting test machine

Now that we have an image to boot, we need a kernel to run. Sadly, a modified kernel is required, since QEMU does not support raspberry pi hardware. Luckily the work of patching and building has already been done by someone else. https://github.com/polaco1782/raspberry-qemu appears to work well.

Clone a copy of that repository and copy kernel-qemu:

$ git clone git@github.com:polaco1782/raspberry-qemu.git
$ cp raspberry-qemu/kernel-qemu .

Now a boot should be possible. Run

$ qemu-system-arm -kernel kernel-qemu \
    -cpu arm1176 \
    -m 256 \
    -M versatilepb \
    -no-reboot \
    -serial stdio \
    -display none \
    -append "root=/dev/sda2 panic=1 rootfstype=ext4 rw" \
    -net user,hostfwd=tcp::10022-:22 \
    -net nic -hda \
    2015-11-21-raspbian-jessie-lite.img