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Converting the Image Format Using qemu-img

Updated at: Dec 10, 2021 GMT+08:00

Scenarios

You can import an image file in VHD, VMDK, QCOW2, RAW, VHDX, QCOW, VDI, QED, ZVHD, or ZVHD2 format to HUAWEI CLOUD. Image files in other formats need to be converted before being imported. The open-source tool qemu-img is provided for you to convert image file formats.

Background

  • qemu-img supports the mutual conversion of image formats VHD, VMDK, QCOW2, RAW, VHDX, QCOW, VDI, and QED.
  • ZVHD and ZVHD2 are self-developed image file formats and cannot be identified by qemu-img. To convert image files to any of the two formats, use the qemu-img-hw tool. For details, see Converting the Image Format Using qemu-img-hw
  • When you run the command to convert the format of VHD image files, use VPC to replace VHD. Otherwise, qemu-img cannot identify the image format.

    For example, to convert a CentOS 6.9 VHD image file into a QCOW2 image file, run the following command:

    qemu-img convert -p -f vpc -O qcow2 centos6.9.vhd centos6.9.qcow2

Windows

  1. Install qemu-img.
    1. Download the qemu-img installation package from https://qemu.weilnetz.de/w64/.
    2. Double-click the setup file to install qemu-img in D:\Program Files\qemu (an example installation path).
  2. Configure environment variables.
    1. Choose Start > Computer and right-click Properties.
    2. Click Advanced system settings.
    3. In the System Properties dialog box, click Advanced > Environment Variables.
    4. In the Environment Variables dialog box, search for Path in the System Variable area and click Edit. Add D:\Program Files\qemu to Variable Value. Use semicolons (;) to separate variable values.

      If Path does not exist, add it and set its value to D:\Program Files\qemu.

    5. Click OK.
  3. Verify the installation.

    Choose Start > Run, enter cmd, and press Enter. In the cmd window, enter qemu-img --help. If the qemu-img version information is contained in the command output, the installation is successful.

  4. Convert the image format.
    1. In the cmd window, run the following commands to switch to D:\Program Files\qemu:

      d:

      cd D:\Program Files\qemu

    1. Run the following command to convert the image file format from VMDK to QCOW2:

      qemu-img convert -p -f vmdk -O qcow2 centos6.9.vmdk centos6.9.qcow2

      The parameters are described as follows:

      • -p indicates the image conversion progress.
      • -f indicates the source image format.
      • The part following -O (which must be in upper case) consists of the required format, source image file, and target image file.

      After the conversion is complete, the target image file is displayed in the directory where the source image file is located.

      The following information is displayed:

      # qemu-img convert -p -f vmdk -O qcow2 centos6.9.vmdk centos6.9.qcow2
          (100.00/100%)
    2. Run the following command to query details about the converted image file in QCOW2 format:

      qemu-img info centos6.9.qcow2

      The following information is displayed:

      # qemu-img info centos6.9.qcow2
      image: centos6.9.qcow2
      file format: qcow2
      virtual size: 1.0G (1073741824 bytes)
      disk size: 200K
      cluster_size: 65536
      Format specific information:
          compat: 1.1
          lazy refcounts: false

Linux

  1. Install qemu-img.
    • For Ubuntu or Debian, run the following command:

      apt install qemu-img

    • For CentOS, Red Hat, or Oracle, run the following command:

      yum install qemu-img

    • For SUSE or openSUSE, run the following command:

      zypper install qemu-img

  2. Run the following command to check whether the installation is successful:

    qemu-img -v

    If the version information and help manual of the qemu-img tool are contained in the command output, the installation is successful. If CentOS 7 is used, the command output is as follows:

    [root@CentOS7 ~]# qemu-img -v
    qemu-img version 1.5.3, Copyright (c) 2004-2008 Fabrice Bellard
    usage: qemu-img command [command options]
    QEMU disk image utility
    
    Command syntax:
      check [-q] [-f fmt] [--output=ofmt] [-r [leaks | all]] [-T src_cache] filename
      create [-q] [-f fmt] [-o options] filename [size]
      commit [-q] [-f fmt] [-t cache] filename
      compare [-f fmt] [-F fmt] [-T src_cach]
  3. Convert the image format. For example, perform the following steps to convert a VMDK image file running CentOS 7 to a QCOW2 image file:
    1. Run the following command to convert the image file format to QCOW2:

      qemu-img convert -p -f vmdk -O qcow2 centos6.9.vmdk centos6.9.qcow2

      The parameters are described as follows:

      • -p: indicates the conversion progress.
      • -f indicates the source image format.
      • The pat following -O (which must be in upper case) is the converted image format + source image file name + target image file name.

      After the conversion is complete, the target image file is displayed in the directory where the source image file is located.

      The following information is displayed:

      [root@CentOS7 home]# qemu-img convert -p -f vmdk -O qcow2 centos6.9.vmdk centos6.9.qcow2
          (100.00/100%)
    2. Run the following command to query details about the converted image file in QCOW2 format:

      qemu-img info centos6.9.qcow2

      The following information is displayed:

      [root@CentOS7 home]# qemu-img info centos6.9.qcow2
      image: centos6.9.qcow2
      file format: qcow2
      virtual size: 1.0G (1073741824 bytes)
      disk size: 200K
      cluster_size: 65536
      Format specific information:
          compat: 1.1
          lazy refcounts: false

Examples

A pre-allocated image depends on two files: xxxx.vmdk (configuration file) and xxxx-flat.vmdk (data file) and cannot be directly imported to the cloud platform. When you export a pre-allocated image file in VMDK monolithic Flat format from the VMware platform, you must convert its format to common VMDK or QCOW2 before it can be imported to the cloud platform.

The following uses the image files centos6.9-64bit-flat.vmdk and centos6.9-64bit.vmdk as an example to describe how to use qemu-img to convert image formats.

  1. Run the following commands to query the image file details:

    ls -lh centos6.9-64bit*

    qemu-img info centos6.9-64bit.vmdk

    qemu-img info centos6.9-64bit-flat.vmdk

    The following information is displayed:

    [root@CentOS7 tmp]# ls -lh centos6.9-64bit*
    -rw-r--r--. 1 root root 10G Jun 13 05:30 centos6.9-64bit-flat.vmdk
    -rw-r--r--. 1 root root 327 Jun 13 05:30 centos6.9-64bit.vmdk
    [root@CentOS7 tmp]# qemu-img info centos6.9-64bit.vmdk
    image: centos6.9-64bit.vmdk
    file format: vmdk
    virtual size: 10G (10737418240 bytes)
    disk size: 4.0K
    Format specific information:
        cid: 3302005459
        parent cid: 4294967295
        create type: monolithicFlat
        extents:
            [0]:
                virtual size: 10737418240
                filename: centos6.9-64bit-flat.vmdk
                format: FLAT
    [root@CentOS7 tmp]# qemu-img info centos6.9-64bit-flat.vmdk
    image: centos6.9-64bit-flat.vmdk
    file format: raw
    virtual size: 10G (10737418240 bytes)
    disk size: 0

    The command output shows that the format of centos6.9-64bit.vmdk is VMDK and that of centos6.9-64bit-flat.vmdk is RAW. You can convert the format of only centos6.9-64bit.vmdk. For details about how to convert it, see 3.

  2. Run the following command to query the configuration of the pre-allocated image file:

    cat centos6.9-64bit.vmdk

    The following information is displayed:

    [root@CentOS7 tmp]# cat centos6.9-64bit.vmdk
    # Disk DescriptorFile
    version=1
    CID=c4d09ad3
    parentCID=ffffffff
    createType="monolithicFlat"
     
    # Extent description
    RW 20971520 FLAT "centos6.9-64bit-flat.vmdk" 0
     
    # The Disk Data Base
    #DDB
     
    ddb.virtualHWVersion = "4"
    ddb.geometry.cylinders = "20805"
    ddb.geometry.heads = "16"
    ddb.geometry.sectors = "63"
    ddb.adapterType = "ide"
  3. Place centos6.9-64bit-flat.vmdk and centos6.9-64bit.vmdk in the same directory. Run the following command to convert the format of centos6.9-64bit.vmdk to QCOW2 using qemu-img:
    [root@CentOS7 tmp]# qemu-img convert -p -f vmdk -O qcow2 centos6.9-64bit.vmdk centos6.9-64bit.qcow2
        (100.00/100%)
  4. Run the following command to query details about the converted image file in QCOW2 format:

    qemu-img info centos6.9-64bit.qcow2

    The following information is displayed:

    [root@CentOS7 tmp]# qemu-img info centos6.9-64bit.qcow2
    image: centos6.9-64bit.qcow2
    file format: qcow2
    virtual size: 10G (10737418240 bytes)
    disk size: 200K
    cluster_size: 65536
    Format specific information:
        compat: 1.1
        lazy refcounts: false

Follow-up Procedure

After the image file format is converted, you can use obsutil to upload the image file to an OBS bucket for creating a private image. For details about how to use obsutil to upload an image file, see Uploading an Object.

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