Allow ISO files larger than 4GiB

[jess-sol]

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Description

Right now due to how mkisofs is called, it's impossible to have files larger than 4GiB in the generated ISO. Consider adding -iso-level 4 which would allow arbitrary file sizes. It may make sense to automatically try -iso-level 4 if the previous attempt without it fails, this way it's backwards compatible.

Use Case(s)

I'm building a Packer file for Windows and need to upload some large installers. Due to the issues with WinRM transferring large files I'm left with the options of HTTP/SSH or CDROM. The CDROM/ISO option is the fastest by far, but doesn't support large files. This would fix that.

Potential configuration

source "qemu" "builder" {
  vm_name          = "windows_2012"
  boot_wait        = "0s"
  accelerator      = "kvm"
  communicator     = "winrm"
  format           = "qcow2"
  cpus             = 2
  disk_size        = var.disk_size
  memory           = var.memory
  headless         = var.headless
  iso_url          = var.iso_url
  iso_checksum     = var.iso_checksum
  shutdown_command = "a:/sysprep.bat"
  output_directory = "dist"
  qemuargs = [
    ["-drive", "file=dist/{{ .Name }},if=virtio,cache=writeback,discard=ignore,format=qcow2,index=1"],
  ]
  winrm_username   = "vagrant"
  winrm_password   = "vagrant"
  winrm_timeout    = var.winrm_timeout
  cd_files = ["large_installer.zip"]
}

Potential References

• https://linux.die.net/man/8/mkisofs