Expand user-image doc

Adds some text on the general instruction on how to build
user-image by virtual machine software.

See also: https://review.opendev.org/#/c/710966/

Change-Id: Ic84bc14ff0bce609009455c644a1601f990a7b45
This commit is contained in:
Kaifeng Wang 2020-03-09 16:38:07 +08:00
parent c6a53b182e
commit cc17246d2b
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@ -26,6 +26,9 @@ the end user. There are two types of user images:
Building user images
^^^^^^^^^^^^^^^^^^^^
disk-image-builder
------------------
The `disk-image-builder`_ can be used to create user images required for
deployment and the actual OS which the user is going to run.
@ -63,3 +66,34 @@ If you want to use Fedora image, replace ``ubuntu`` with ``fedora`` in the
chosen command.
.. _disk-image-builder: https://docs.openstack.org/diskimage-builder/latest/
Virtual machine
---------------
Virtual machine software can also be used to build user images. There are
different software options available, qemu-kvm is usually a good choice on
linux platform, it supports emulating many devices and even building images
for architectures other than the host machine by software emulation.
VirtualBox is another good choice for non-linux host.
The procedure varies depending on the software used, but the steps for
building an image are similar, the user creates a virtual machine, and
installs the target system just like what is done for a real hardware. The
system can be highly customized like partition layout, drivers or software
shipped, etc.
Usually libvirt and its management tools are used to make interaction with
qemu-kvm easier, for example, to create a virtual machine with
``virt-install``::
$ virt-install --name centos8 --ram 4096 --vcpus=2 -f centos8.qcow2 \
> --cdrom CentOS-8-x86_64-1905-dvd1.iso
Graphic frontend like ``virt-manager`` can also be utilized.
The disk file can be used as user image after the system is set up and powered
off. The path of the disk file varies depending on the software used, usually
it's stored in a user-selected part of the local file system. For qemu-kvm or
GUI frontend building upon it, it's typically stored at
``/var/lib/libvirt/images``.