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# Running Ubuntu 16.04.1 armhf on Qemu |
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This is a writeup about how to install [Ubuntu 16.04.1 Xenial Xerus](https://wiki.ubuntu.com/XenialXerus/ReleaseNotes) for the 32-bit hard-float ARMv7 (armhf) architecture on a Qemu VM via [Ubuntu netboot](http://cdimage.ubuntu.com/netboot/16.04.1/). |
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The setup will create a Ubuntu VM with [LPAE](https://www.arm.com/products/processors/technologies/virtualization-extensions.php) extensions (generic-lpae) enabled. However, this writeup should also work for non-LPAE (generic) kernels. |
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The performance of the resulting VM is quite good, and it allows VMs with >1G ram (compared to 256M on `versatilepb` and 1G on `versatile-a9`/`versatile-a15`). It also supports `virtio` disks whereas `versatile-a9`/`versatile-a15` only support SD cards via the `-sd` argument. |
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## Get netboot files |
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The netboot files are available on the official [Ubuntu mirror](http://ports.ubuntu.com/ubuntu-ports/dists/xenial/main/installer-armhf/current/images/generic-lpae/netboot/). The following commands will download the kernel (vmlinuz) and initrd (initrd.gz) in a new directory called `netboot`: |
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```bash |
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mkdir netboot |
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cd netboot |
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wget -r -nH -nd -np -R "index.html*" --quiet http://ports.ubuntu.com/ubuntu-ports/dists/xenial/main/installer-armhf/current/images/generic-lpae/netboot/ |
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``` |
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## Create a image file |
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The following command creates a image file that will be used as a disk for the Ubuntu system: |
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```bash |
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qemu-img create -f qcow2 ubuntu.img 16G |
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``` |
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## Setup networking |
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Installing Ubuntu via netboot requires an Internet connection. Therefore the Ubuntu VM requires a network intefaces that can use the Internet connection of the host system. The host systems needs to create a tuntap device for the VM and a bridge that will connect the tuntap interface with the Internet-facing interface. The bridge is called `br0` and the tuntap device for the Ubuntu VM will be `tap0`. |
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```bash |
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sudo ip tuntap add dev tap0 mode tap |
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sudo ip link set up dev tap0 |
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sudo ip link set tap0 master br0 |
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``` |
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Creating a bridge and adding the Internet-facing interface (e.g. `eth0`): |
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```bash |
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sudo ip link add br0 type bridge |
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sudo ip link set eth0 master br0 |
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``` |
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Allow IP packet forwarding: |
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```bash |
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sudo sysctl -w net.ipv4.ip_forward=1 |
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``` |
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Start a DHCP server in the bridge so that the Ubuntu VM receives an IP address: |
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```bash |
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echo "subnet 192.168.0.0 netmask 255.255.255.0 { |
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range 192.168.0.10 192.168.0.100; |
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option routers 192.168.0.1; |
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option domain-name-servers 208.67.222.222, 208.67.220.220; |
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}" > qemu-dhcpd.conf |
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sudo dhcpd -cf qemu-dhcpd.conf br0 |
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``` |
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## Start the netboot installation |
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From the netboot directory (containing the netboot files `vmlinuz` and `initrd.gz`), run the following command: |
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```bash |
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qemu-system-arm \ |
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-kernel vmlinuz \ |
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-initrd initrd.gz \ |
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-append "root=/dev/ram" \ |
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-no-reboot \ |
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-nographic \ |
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-m 1024 \ |
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-M virt \ |
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-serial stdio \ |
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-net nic \ |
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-net tap,ifname=tap0,script=no,downscript=no \ |
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-hda ubuntu.img |
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``` |
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The kernel should now boot into the Ubuntu installer within the terminal window where the command has been executed. |
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## Extract the new kernel |
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After the installation process has been finished, extract the kernel and initrd files from the new installed Ubuntu system. Mount the Ubuntu image: |
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```bash |
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qemu-img convert -f qcow2 -O raw ubuntu.img ubuntu-raw.img |
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sudo losetup /dev/loop0 ubuntu-raw.img |
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OFFSET=$(($(sudo fdisk -l /dev/loop0 |grep /dev/loop0p1 |awk '{print $3}')*512)) |
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sudo mount -o loop,offset=$OFFSET /dev/loop0 /mnt |
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``` |
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Create a new directory `boot` for the new kernel and initrd files and copy them into it: |
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```bash |
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mkdir boot |
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cp /mnt/initrd.img-4.4.0-38-generic-lpae |
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cp /mnt/vmlinuz-4.4.0-38-generic-lpae boot |
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``` |
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Cleanup: |
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```bash |
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sudo umount /mnt |
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sudo losetup -d /dev/loop0 |
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rm ubuntu-raw.img |
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``` |
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*TODO*: Add working solution that does not require to convert the image file. |
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## Start the Ubuntu VM |
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The Ubuntu VM directory should now have the following structure: |
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```bash |
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├── boot |
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│ ├── initrd.img-4.4.0-38-generic-lpae |
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│ └── vmlinuz-4.4.0-38-generic-lpae |
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├── netboot |
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│ ├── initrd.gz |
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│ └── vmlinuz |
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└── ubuntu.img |
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``` |
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Start Qemu: |
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```bash |
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qemu-system-arm \ |
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-kernel boot/vmlinuz-4.4.0-38-generic-lpae \ |
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-initrd boot/initrd.img-4.4.0-38-generic-lpae \ |
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-append "root=/dev/vda2 rootfstype=ext4" \ |
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-no-reboot \ |
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-nographic \ |
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-m 1024 \ |
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-M virt \ |
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-serial stdio \ |
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-monitor telnet:127.0.0.1:9000,server,nowait \ |
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-net nic \ |
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-net tap,ifname=tap0,script=no,downscript=no \ |
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-drive file=ubuntu.img,if=virtio |
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``` |
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The following script can be used for starting the VM: |
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```bash |
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#!/bin/sh |
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NET_IF=tap0 |
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BRIDGE=br0 |
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if ! grep --quiet $NET_IF /proc/net/dev;then |
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echo "Creating ${NET_IF} device" |
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sudo ip tuntap add dev $NET_IF mode tap |
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sudo ip l s up dev $NET_IF |
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fi |
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if grep --quiet $BRIDGE /proc/net/dev;then |
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sudo ip l s $NET_IF master $BRIDGE |
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else |
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echo "${BRIDGE} does not exist!" |
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exit |
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fi |
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qemu-system-arm \ |
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-kernel boot/vmlinuz-4.4.0-38-generic-lpae \ |
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-initrd boot/initrd.img-4.4.0-38-generic-lpae \ |
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-append "root=/dev/vda2 rootfstype=ext4" \ |
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-no-reboot \ |
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-nographic \ |
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-m 1024 \ |
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-M virt \ |
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-serial stdio \ |
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-monitor telnet:127.0.0.1:9000,server,nowait \ |
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-net nic \ |
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-net tap,ifname=tap0,script=no,downscript=no \ |
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-drive file=ubuntu.img,if=virtio |
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``` |
takeshixx revised this gist