# How to create a custom Ubuntu image In the context of adding more utilities to the Ubuntu cloud image being used for integration testing, this quick guide details how to achieve the proper modification of an official Ubuntu cloud image. ## Create the image Let's go through the steps on how to extend an official Ubuntu image. These steps can be applied to other distributions (with a few changes regarding package management). ### Get latest Ubuntu cloud image ```bash wget https://cloud-images.ubuntu.com/focal/current/focal-server-cloudimg-amd64.img ``` ### Check the file format is QCOW2 ```bash file focal-server-cloudimg-amd64.img focal-server-cloudimg-amd64.img: QEMU QCOW2 Image (v2), 2361393152 bytes ``` ### Convert QCOW2 into RAW ```bash qemu-img convert -p -f qcow2 -O raw focal-server-cloudimg-amd64.img focal-server-cloudimg-amd64.raw ``` ### Identify the Linux partition The goal is to mount the image rootfs so that it can be modified as needed. That's why we need to identify where the Linux filesystem partition is located in the image. ```bash sudo fdisk -l focal-server-cloudimg-amd64.raw Disk focal-server-cloudimg-amd64.raw: 2.2 GiB, 2361393152 bytes, 4612096 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: gpt Disk identifier: A1171ABA-2BEA-4218-A467-1B2B607E5953 Device Start End Sectors Size Type focal-server-cloudimg-amd64.raw1 227328 4612062 4384735 2.1G Linux filesystem focal-server-cloudimg-amd64.raw14 2048 10239 8192 4M BIOS boot focal-server-cloudimg-amd64.raw15 10240 227327 217088 106M EFI System Partition table entries are not in disk order. ``` ### Mount the Linux partition ```bash mkdir -p /mnt sudo mount -o loop,offset=$((227328 * 512)) focal-server-cloudimg-amd64.raw /mnt ``` ### Set up DNS The next step describes changing the root directory to the rootfs contained by the cloud image. For DNS to work in the root directory, you will need to first bind-mount the host `/etc/resolv.conf` onto the mounted linux partition of the cloud image. ```bash sudo mount -o bind /etc/resolv.conf /mnt/etc/resolv.conf ``` ### Change root directory Changing the root directory will allow us to install new packages to the rootfs contained by the cloud image. ```bash sudo chroot /mnt mount -t proc proc /proc mount -t devpts devpts /dev/pts ``` ### Install needed packages In the context Cloud Hypervisor's integration tests, we need several utilities. Here is the way to install them for a Ubuntu image. This step is specific to Ubuntu distributions. ```bash apt update apt install fio iperf iperf3 socat stress cpuid tpm2-tools ``` ### Remove counterproductive packages * snapd: This prevents snapd from trying to mount squashfs filesystem when the kernel might not support it. This might be the case when the image is used with direct kernel boot. This step is specific to Ubuntu distributions. * pollinate: Remove this package which can fail and lead to the SSH daemon failing to start. See #2113 for details. ```bash apt remove --purge snapd pollinate ``` ### Cleanup the image Leave no trace in the image before unmounting its content. ```bash umount /dev/pts umount /proc history -c exit umount /mnt/etc/resolv.conf umount /mnt ``` ### Rename the image Renaming is important to identify this is a modified image. ```bash mv focal-server-cloudimg-amd64.raw focal-server-cloudimg-amd64-custom-$(date "+%Y%m%d")-0.raw ``` The `-0` is the revision and is only necessary to change if multiple images are updated on the same day. ### Create QCOW2 from RAW Last step is to create the QCOW2 image back from the modified image. ```bash qemu-img convert -p -f raw -O qcow2 focal-server-cloudimg-amd64-custom-$(date "+%Y%m%d")-0.raw focal-server-cloudimg-amd64-custom-$(date "+%Y%m%d")-0.qcow2 ``` ## Switch CI to use the new image ### Upload to Azure storage The next step is to update both images (QCOW2 and RAW) stored as part of the Azure storage account, replacing them with the newly created ones. This will make these new images available from the integration tests. This is usually achieved through the web interface. ### Update integration tests Last step is about updating the integration tests to work with this new image. The key point is to identify where the Linux filesystem partition is located, as we might need to update the direct kernel boot command line, replacing `/dev/vda1` with the appropriate partition number. Update all references to the previous image name to the new one. ## NVIDIA image for VFIO bare-metal CI Here we are going to describe how to create a cloud image that contains the necessary NVIDIA drivers for our VFIO bare-metal CI. ### Download base image We usually start from one of the custom cloud image we have previously created but we can use a stock cloud image as well. ```bash wget https://ch-images.azureedge.net/jammy-server-cloudimg-amd64-custom-20230119-0.raw mv jammy-server-cloudimg-amd64-custom-20230119-0.raw jammy-server-cloudimg-amd64-nvidia.raw ``` ### Extend the image size The NVIDIA drivers consume lots of space, which is why we must resize the image before we proceed any further. ```bash qemu-img resize jammy-server-cloudimg-amd64-nvidia.raw 5G ``` ### Resize the partition We use `parted` for fixing the GPT after the image was resized, as well as for resizing the `Linux` partition. ```bash sudo parted jammy-server-cloudimg-amd64-nvidia.raw (parted) print Warning: Not all of the space available to jammy-server-cloudimg-amd64-nvidia.raw appears to be used, you can fix the GPT to use all of the space (an extra 5873664 blocks) or continue with the current setting? Fix/Ignore? Fix Model: (file) Disk jammy-server-cloudimg-amd64-nvidia.raw: 5369MB Sector size (logical/physical): 512B/512B Partition Table: gpt Disk Flags: Number Start End Size File system Name Flags 14 1049kB 5243kB 4194kB bios_grub 15 5243kB 116MB 111MB fat32 boot, esp 1 116MB 2361MB 2245MB ext4 (parted) resizepart 1 5369MB (parted) print Model: (file) Disk jammy-server-cloudimg-amd64-nvidia.raw: 5369MB Sector size (logical/physical): 512B/512B Partition Table: gpt Disk Flags: Number Start End Size File system Name Flags 14 1049kB 5243kB 4194kB bios_grub 15 5243kB 116MB 111MB fat32 boot, esp 1 116MB 5369MB 5252MB ext4 (parted) quit ``` ### Create a macvtap interface Rely on the following [documentation](macvtap-bridge.md) to set up a macvtap interface to provide your VM with proper connectivity. ### Boot the image It is particularly important to boot with a `cloud-init` disk attached to the VM as it will automatically resize the Linux `ext4` filesystem based on the partition that we have previously resized. ```bash ./cloud-hypervisor \ --kernel hypervisor-fw \ --disk path=focal-server-cloudimg-amd64-nvidia.raw path=/tmp/ubuntu-cloudinit.img \ --cpus boot=4 \ --memory size=4G \ --net fd=3,mac=$mac 3<>$"$tapdevice" ``` ### Bring up connectivity If your network has a DHCP server, run the following from your VM ```bash sudo dhclient ``` But if that's not the case, let's give it an IP manually (the IP addresses depend on your actual network) and set the DNS server IP address as well. ```bash sudo ip addr add 192.168.2.10/24 dev ens4 sudo ip link set up dev ens4 sudo ip route add default via 192.168.2.1 sudo resolvectl dns ens4 8.8.8.8 ``` #### Check connectivity and update the image ```bash sudo apt update sudo apt upgrade ``` ### Install NVIDIA drivers The following steps and commands are referenced from the [NVIDIA official documentation](https://docs.nvidia.com/datacenter/tesla/tesla-installation-notes/index.html#ubuntu-lts) about Tesla compute cards. ```bash distribution=$(. /etc/os-release;echo $ID$VERSION_ID | sed -e 's/\.//g') wget https://developer.download.nvidia.com/compute/cuda/repos/$distribution/x86_64/cuda-keyring_1.0-1_all.deb sudo dpkg -i cuda-keyring_1.0-1_all.deb sudo apt-key del 7fa2af80 sudo apt update sudo apt -y install cuda-drivers ``` ### Check the `nvidia-smi` tool Quickly validate that you can find and run the `nvidia-smi` command from your VM. At this point it should fail given no NVIDIA card has been passed through the VM, therefore no NVIDIA driver is loaded. ### Workaround LA57 reboot issue Add `reboot=a` to `GRUB_CMDLINE_LINUX` in `etc/default/grub` so that the VM will be booted with the ACPI reboot type. This resolves a reboot issue when running on 5-level paging systems. ```bash sudo vim /etc/default/grub sudo update-grub sudo reboot ``` ### Remove previous logins Since our integration tests rely on past logins to count the number of reboots, we must ensure to clear the list. ```bash >/var/log/lastlog >/var/log/wtmp >/var/log/btmp ``` ### Clear history ``` history -c rm /home/cloud/.bash_history ``` ### Reset cloud-init This is mandatory as we want `cloud-init` provisioning to work again when a new VM will be booted with this image. ``` sudo cloud-init clean ```