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Now that the project relies on Ubuntu images, the documentation related to the creation of a custom image has been updated. It's important to note this procedure could be applied to any other distribution, given that the package manager's commands would be slightly different. Signed-off-by: Sebastien Boeuf <sebastien.boeuf@intel.com>
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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
wget https://cloud-images.ubuntu.com/focal/current/focal-server-cloudimg-amd64.img
Check the file format is QCOW2
file focal-server-cloudimg-amd64.img
focal-server-cloudimg-amd64.img: QEMU QCOW2 Image (v2), 2361393152 bytes
Convert QCOW2 into RAW
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.
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
mkdir -p /mnt
sudo mount -o loop,offset=$((227328 * 512)) focal-server-cloudimg-amd64.raw /mnt
Change root directory
Changing the root directory will allow us to install new packages to the rootfs contained by the cloud image.
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.
apt update
apt install fio iperf iperf3 socat
Remove 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.
apt remove --purge snapd
Cleanup the image
Leave no trace in the image before unmounting its content.
umount /dev/pts
umount /proc
history -c
exit
umount /mnt
Rename the image
Renaming is important to identify this is a modified image.
mv focal-server-cloudimg-amd64.raw focal-server-cloudimg-amd64-custom.raw
Create QCOW2 from RAW
Last step is to create the QCOW2 image back from the modified image.
qemu-img convert -p -f raw -O qcow2 focal-server-cloudimg-amd64-custom.raw focal-server-cloudimg-amd64-custom.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.