Capi Ubuntu 22.04 image built with Qemu are big

[chess-knight]

What steps did you take and what happened:

• Built an Ubuntu 22.04 image using the qemu provider
• Created image has 10-15 GB disk size

What did you expect to happen:
Ubuntu qcow2 image has a small disk size

Anything else you would like to add:

• I tried it with many different Kubernetes versions but the disk remains big
• See also #1137 with the same experience
• I did these steps and:

  $ qemu-img info output/ubuntu-2204-kube-v1.26.3/ubuntu-2204-kube-v1.26.3
  image: output/ubuntu-2204-kube-v1.26.3/ubuntu-2204-kube-v1.26.3
  file format: qcow2
  virtual size: 20G (21474836480 bytes)
  disk size: 12G
  cluster_size: 65536
  Format specific information:
      compat: 1.1
      lazy refcounts: false
      refcount bits: 16
      corrupt: false
  

• It seems like packer qcow2 compaction doesn't work properly, when I run qemu-img convert -O qcow2 output/ubuntu-2204-kube-v1.26.3/ubuntu-2204-kube-v1.26.3 output/ubuntu-2204-kube-v1.26.3/ubuntu-2204-kube-v1.26.3-compact the qemu-img info command has same output(disk size: 12G)
• But when I run virt-sparsify output/ubuntu-2204-kube-v1.26.3/ubuntu-2204-kube-v1.26.3 output/ubuntu-2204-kube-v1.26.3/ubuntu-2204-kube-v1.26.3-sparse then the disk size seems fine:

  $ qemu-img info output/ubuntu-2204-kube-v1.26.3/ubuntu-2204-kube-v1.26.3-sparse 
  image: output/ubuntu-2204-kube-v1.26.3/ubuntu-2204-kube-v1.26.3-sparse
  file format: qcow2
  virtual size: 20G (21474836480 bytes)
  disk size: 4.6G
  cluster_size: 65536
  Format specific information:
      compat: 1.1
      lazy refcounts: false
      refcount bits: 16
      corrupt: false
  

• Maybe we can try "disk_detect_zeroes": "unmap" in the packer qemu options, but I do not know if it should help at all
• I also noticed, that in Ubuntu 22.04 the /swapfile was renamed to /swap.img(it has 2GB for mentioned image) and is not deleted
  • Maybe we can use this(see Action-based config section) to disable swap completely:

    autoinstall:
      storage:
        swap:
          size: 0
    

Environment:

Project Image Builder for Cluster API:

Additional info for Image Builder for Cluster API related issues:

• OS (e.g. from /etc/os-release, or cmd /c ver): Ubuntu 18.04.6 LTS
• Packer Version: v1.8.3
• Packer Provider: QEMU
• Ansible Version: 2.9.27
• Cluster-api version (if using):
• Kubernetes version: (use kubectl version): 1.26.3

/kind bug