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https://github.com/cloud-hypervisor/cloud-hypervisor.git
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e6e58e6d66
The proper way to refer to the project is "Cloud Hypervisor" without the hyphen in the middle. On the other hand, if one refers to the binary name, it is "cloud-hypervisor". Signed-off-by: Sebastien Boeuf <sebastien.boeuf@intel.com>
150 lines
4.2 KiB
Markdown
150 lines
4.2 KiB
Markdown
# How to create a custom Ubuntu image
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In the context of adding more utilities to the Ubuntu cloud image being used
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for integration testing, this quick guide details how to achieve the proper
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modification of an official Ubuntu cloud image.
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## Create the image
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Let's go through the steps on how to extend an official Ubuntu image. These
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steps can be applied to other distributions (with a few changes regarding
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package management).
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### Get latest Ubuntu cloud image
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```bash
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wget https://cloud-images.ubuntu.com/focal/current/focal-server-cloudimg-amd64.img
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```
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### Check the file format is QCOW2
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```bash
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file focal-server-cloudimg-amd64.img
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focal-server-cloudimg-amd64.img: QEMU QCOW2 Image (v2), 2361393152 bytes
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```
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### Convert QCOW2 into RAW
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```bash
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qemu-img convert -p -f qcow2 -O raw focal-server-cloudimg-amd64.img focal-server-cloudimg-amd64.raw
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```
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### Identify the Linux partition
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The goal is to mount the image rootfs so that it can be modified as needed.
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That's why we need to identify where the Linux filesystem partition is located
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in the image.
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```bash
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sudo fdisk -l focal-server-cloudimg-amd64.raw
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Disk focal-server-cloudimg-amd64.raw: 2.2 GiB, 2361393152 bytes, 4612096 sectors
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Units: sectors of 1 * 512 = 512 bytes
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Sector size (logical/physical): 512 bytes / 512 bytes
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I/O size (minimum/optimal): 512 bytes / 512 bytes
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Disklabel type: gpt
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Disk identifier: A1171ABA-2BEA-4218-A467-1B2B607E5953
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Device Start End Sectors Size Type
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focal-server-cloudimg-amd64.raw1 227328 4612062 4384735 2.1G Linux filesystem
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focal-server-cloudimg-amd64.raw14 2048 10239 8192 4M BIOS boot
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focal-server-cloudimg-amd64.raw15 10240 227327 217088 106M EFI System
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Partition table entries are not in disk order.
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```
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### Mount the Linux partition
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```bash
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mkdir -p /mnt
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sudo mount -o loop,offset=$((227328 * 512)) focal-server-cloudimg-amd64.raw /mnt
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```
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### Change root directory
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Changing the root directory will allow us to install new packages to the rootfs
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contained by the cloud image.
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```bash
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sudo chroot /mnt
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mount -t proc proc /proc
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mount -t devpts devpts /dev/pts
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```
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### Install needed packages
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In the context Cloud Hypervisor's integration tests, we need several utilities.
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Here is the way to install them for a Ubuntu image. This step is specific to
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Ubuntu distributions.
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```bash
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apt update
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apt install fio iperf iperf3 socat stress
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```
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### Remove counterproductive packages
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* snapd:
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This prevents snapd from trying to mount squashfs filesystem when the kernel
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might not support it. This might be the case when the image is used with direct
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kernel boot. This step is specific to Ubuntu distributions.
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* pollinate:
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Remove this package which can fail and lead to the SSH daemon failing to start.
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See #2113 for details.
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```bash
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apt remove --purge snapd pollinate
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```
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### Cleanup the image
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Leave no trace in the image before unmounting its content.
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```bash
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umount /dev/pts
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umount /proc
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history -c
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exit
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umount /mnt
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```
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### Rename the image
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Renaming is important to identify this is a modified image.
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```bash
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mv focal-server-cloudimg-amd64.raw focal-server-cloudimg-amd64-custom-$(date "+%Y%m%d")-0.raw
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```
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The `-0` is the revision and is only necessary to change if multiple images are
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updated on the same day.
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### Create QCOW2 from RAW
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Last step is to create the QCOW2 image back from the modified image.
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```bash
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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
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```
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## Switch CI to use the new image
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### Upload to Azure storage
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The next step is to update both images (QCOW2 and RAW) stored as part of the
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Azure storage account, replacing them with the newly created ones. This will
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make these new images available from the integration tests. This is usually
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achieved through the web interface.
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### Update integration tests
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Last step is about updating the integration tests to work with this new image.
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The key point is to identify where the Linux filesystem partition is located,
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as we might need to update the direct kernel boot command line, replacing
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`/dev/vda1` with the appropriate partition number.
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Update all references to the previous image name to the new one.
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