Cloud images are not resized according to the required disk size

[galdor]

In the current state (vm-bhyve 1.5), vm created from a cloud image have a disk whose size is the virtual size of the cloud image size.

For example:

vm img https://cloud-images.ubuntu.com/releases/22.04/release/ubuntu-22.04-server-cloudimg-amd64.img
vm create -i ubuntu-22.04-server-cloudimg-amd64.img -s 100G

This creates a VM whose disk is 2.2GB, which is the virtual size of the Ubuntu cloud image (check with qemu-img info <vm-path>/.img/ubuntu-22.04-server-cloudimg-amd64.img), even though we expect a VM with a 100GB disk.

One way to fix this would be to use qemu-img resize. But since we probably do not want to touch the original image, would it be acceptable to modify core::write_img to:

• Copy $_imgpath to ${img_path}.tmp.
• Call qemu-img resize ${img_path}.tmp $_size.
• Run qemu-img dd on the temporary image.
• Delete the temporary image.

Of course it would mean extra disk usage during the operation. I do not think this is a huge deal, but someone may have a better idea.

I can write the patch if maintainers (who are they?) agree.

[sarcasticadmin]

I just ran into this as well with some of my testing. I had this issue while using the default value for disk0_dev=file in my template. This does not seem to be an issue for disk0_dev=sparse-zvol or disk0_dev=zvol which still honor disk0_size.

Simplest way Ive been able to reproduce this behavior was to manually do what the vm create command does when disk0_dev=file in a template.

Starting with my raw image:

~ # ls -lah myimage.img 
-rw-r--r--  1 root  wheel   2.4G Dec 29 09:40 myimage.img

Create the disk:

~ # truncate -s 10G disk0
~ # ls -lah disk0 
-rw-r--r--  1 root  wheel    10G Dec 29 09:15 disk0

Write the image to it:

~ # qemu-img dd -O raw if=myimage.img of=./disk0 bs=1M
~ # ls -lah disk0
-rw-r--r--  1 root  wheel   2.4G Dec 29 09:39 disk0

Refs in the codebase:

• vm-bhyve/lib/vm-core

  Line 228 in bda366b

  truncate -s "${_disk_size}" "${VM_DS_PATH}/${_name}/${_disk}"

• vm-bhyve/lib/vm-core

  Line 342 in bda366b

  qemu-img dd -O raw if="${_imgpath}" of="${_disk_dev}" bs=1M

~ # vm version
vm-bhyve: Bhyve virtual machine management v1.6-devel (rev. 106001)
~ # qemu-img --version
qemu-img version 7.1.0
Copyright (c) 2003-2022 Fabrice Bellard and the QEMU Project developers

[mateuszkwiatkowski]

This is tracked in new issue: #535