lima-vm/lima · error

base disk (%#q) must not have multiple children: %+v

Error message

base disk (%#q) must not have multiple children: %+v

What it means

AcceptableAsBaseDisk rejects base disks that report more than one child in `qemu-img info` output (Children populated since QEMU 8.0). Multiple children means the image has several attached references — e.g. multiple VMDK extents whose filenames differ, or an image opened with multiple links — which Lima cannot verify as self-contained, so it fails closed rather than allow untrusted external file references into the guest disk.

Source

Thrown at pkg/qemuimgutil/qemuimgutil.go:292

		logrus.WithField("filename", info.Filename).
			Warnf("Unsupported image format %#q. The image may not boot, or may have an extra privilege to access the host filesystem. Use with caution.", info.Format)
	}
	if err := rejectExternalFileReferences(info); err != nil {
		return err
	}
	// info.Children is set since QEMU 8.0
	switch len(info.Children) {
	case 0:
	// NOP
	case 1:
		if info.Filename != info.Children[0].Info.Filename {
			return fmt.Errorf("base disk (%#q) child must not have a different filename (%#q)", info.Filename, info.Children[0].Info.Filename)
		}
		if len(info.Children[0].Info.Children) > 0 {
			return fmt.Errorf("base disk (%#q) child must not have children of its own", info.Filename)
		}
	default:
		return fmt.Errorf("base disk (%#q) must not have multiple children: %+v", info.Filename, info.Children)
	}
	return nil
}

View on GitHub (pinned to dd909d0973)

Solutions

1. Convert the image to a single-file qcow2: `qemu-img convert -O qcow2 image.vmdk image.qcow2`, ensuring all extents are in one directory or embedded during conversion.
2. If the source is a split VMDK, re-download/re-export it as a monolithic (single-file) VMDK or directly as qcow2/raw, then retry.
3. Verify with `qemu-img info image.qcow2` that children/backing files are gone before using it as a base disk.

Example fix

// before: split VMDK (disk-s001.vmdk, disk-s002.vmdk, ...) used as base disk
// after
//   qemu-img convert -O qcow2 disk.vmdk disk.qcow2   # monolithic conversion
//   # qemu-img info disk.qcow2 -> no children, single self-contained file

// Before use, confirm the image is single-file:
// qemu-img info --output=json image.vmdk | jq '.children | length <= 1'
// For VMDK sources, prefer monolithic export or convert first:
// qemu-img convert -O qcow2 image.vmdk image.qcow2

func singleChildMax(info Info) bool {
	return len(info.Children) <= 1
}

When it happens

Trigger: Calling AcceptableAsBaseDisk (via EnsureDisk) on an image whose qemu-img info JSON contains 2+ entries in info.Children — e.g. a streamOptimized/split VMDK with multiple external extent files, or any format exposing multiple child nodes.

Common situations: Importing a split VMDK (multiple -s001.vmdk extent files) converted only partially to qcow2; using an image produced by a hypervisor export that kept multi-file layout; inspecting an image with QEMU 8.0+ where the multi-child structure becomes visible.

Related errors

• base disk (%#q) child must not have a different filename (%#
• base disk (%#q) child must not have children of its own
• configuration is nil
• field `vmOpts.qemu.minimumVersion` must be a semvar value, g
• mount type %#q is explicitly unsupported

AI-assisted analysis of lima-vm/lima@dd909d0973 (2026-09-01). Data as JSON: /api/errors/5040879c0c55d1a1. Report an issue: GitHub.