Emulate Raspberry Pi with QEMU

Preparation

We need a proper kernel and the Arch Linux ARM distro for the Raspberry Pi system. You can get both using wget:

wget https://github.com/dhruvvyas90/qemu-rpi-kernel/raw/master/kernel-qemu-4.4.34-jessie
wget http://os.archlinuxarm.org/os/ArchLinuxARM-rpi-latest.tar.gz

Check the qemu-rpi-kernel github page for a more recent kernel if needed.

Image creation

Choose an appropriate size for your image, I'll go for 8 GiB in this example:

dd if=/dev/zero of=Arch.img count=8192 bs=1048576

We create two partitions inside the image, one 100 MiB partition for /boot and one / partition filling the rest of the image:

fdisk ./Arch.img
  Command (m for help): n
    Partition type
      p   primary (0 primary, 0 extended, 4 free)
      e   extended (container for logical partitions)
    Select (default p): p
    Partition number (1-4, default 1):
    First sector (2048-16777215, default 2048):
    Last sector, +sectors or +size{K,M,G,T,P} (2048-16777215, default 16777215): +100M

    Created a new partition 1 of type 'Linux' and of size 100 MiB.

    Command (m for help): n
    Partition type
      p   primary (1 primary, 0 extended, 3 free)
      e   extended (container for logical partitions)
    Select (default p): p
    Partition number (2-4, default 2):
    First sector (206848-16777215, default 206848):
    Last sector, +sectors or +size{K,M,G,T,P} (206848-16777215, default 16777215):

    Created a new partition 2 of type 'Linux' and of size 7.9 GiB.

    Command (m for help): w

Arch Linux ARM installation

Using losetup and partx, we setup a loop device for the image and add specific partitions:

su -c 'losetup -f --show Arch.img'
su -c 'partx -a /dev/loop0'

The partitions are now accessible as /dev/loop0p1 and /dev/loop0p2 within the local filesystem. Time to create an appropriate filesystem for each partition. We choose FAT for the /boot partition and ext4 for the / partition.

su -c 'mkfs.vfat /dev/loop0p1'
su -c 'mkfs.ext4 /dev/loop0p2'

We are now able to locally mount both partitions:

mkdir boot root
su -c 'mount /dev/loop0p1 boot/'
su -c 'mount /dev/loop0p2 root/'

The following commands install Arch Linux ARM to the image:

su -c 'bsdtar -xpf ArchLinuxARM-rpi-latest.tar.gz -C root/'
su -c 'mv root/boot/* boot/'

Since ArchLinuxARM-rpi-latest.tar.gz was created to fit onto a SD Card, the fstab file does not yet fit our needs. Without the following changes to fstab, the kernel would not find the partitions:

emacs root/etc/fstab

# Static information about the filesystems.
# See fstab(5) for details.

# <file system>  <dir>   <type>  <options>      <dump>  <pass>
-/dev/mmcblk0p1  /boot   vfat    defaults        0       0
+/dev/sda1       /boot   vfat    defaults        0       0
+/dev/sdb2       /       ext4    defaults        0       0

Now unmount the partitions and clean up things:

su -c 'umount /dev/loop0p1'
su -c 'umount /dev/loop0p2'
su -c 'partx -d /dev/loop0'
su -c 'losetup -d /dev/loop0'

Run the guest system

Let's finally run the Raspberry Pi image with qemu-system-arm:

qemu-system-arm -kernel kernel-qemu-4.4.34-jessie -cpu arm1176 -m 256 -M versatilepb -serial stdio -append "root=/dev/sda2 rootfstype=ext4 rw" -hda Arch.img -net nic,macaddr=de:ad:be:ef:ca:fe -net user,hostfwd=tcp::5555-:22

Note from the command above, that qemu will forward the guest's TCP port 22 (SSH) to the host TCP port 5555. Login into your guest system as root and activate the SSH server:

systemctl enable sshd
systemctl start sshd

Now you should be able to SSH from your host into your guest system:

ssh -p 5555 alarm@127.0.0.1

Related links (Standing on the shoulders of giants)

• azeria-labs.com: RASPBERRY PI ON QEMU

• QEMU versatilepb default network adapter