8d2d9c214c
A vmx image is the same disk as an oem just without the dracut repart/resize feature. This difference is better handled with an oemconfig parameter <oem-resize> which allows to switch resize on or off. The extra image type vmx will be dropped and an XSLT stylesheet automatically transforms a vmx description to be a oem image with the resize feature switched off. This Fixes #1425
86 lines
3.4 KiB
ReStructuredText
86 lines
3.4 KiB
ReStructuredText
.. _ramdisk_deployment:
|
|
|
|
Deploy and Run System in a RamDisk
|
|
==================================
|
|
|
|
.. sidebar:: Abstract
|
|
|
|
This page provides further information for handling
|
|
oem images built with {kiwi} and references the following
|
|
articles:
|
|
|
|
* :ref:`expandable_disk`
|
|
|
|
If a machine should run the OS completely in memory without
|
|
the need for any persistent storage, the approach to deploy
|
|
the image into a ramdisk serves this purpose. {kiwi} allows
|
|
to create a bootable ISO image which deploys the image
|
|
into a ramdisk and activates that image with the following
|
|
oem type definition:
|
|
|
|
.. code:: xml
|
|
|
|
<type image="oem" filesystem="ext4" installiso="true" initrd_system="dracut" installboot="install" kernelcmdline="rd.kiwi.ramdisk ramdisk_size=2048000">
|
|
<bootloader name="grub2" timeout="1"/>
|
|
<oemconfig>
|
|
<oem-skip-verify>true</oem-skip-verify>
|
|
<oem-unattended>true</oem-unattended>
|
|
<oem-unattended-id>/dev/ram1</oem-unattended-id>
|
|
<oem-swap>false</oem-swap>
|
|
<oem-multipath-scan>false</oem-multipath-scan>
|
|
</oemconfig>
|
|
</type>
|
|
|
|
The type specification above builds an installation ISO image
|
|
which deploys the System Image into the specified ramdisk
|
|
device (/dev/ram1). The setup of the ISO image boots with a
|
|
short boot timeout of 1sec and just runs through the process
|
|
without asking any questions. In a ramdisk deployment the
|
|
optional target verification, swap space and multipath targets
|
|
are out of scope and therefore disabled.
|
|
|
|
The configured size of the ramdisk specifies the size of the
|
|
OS disk and must be at least of the size of the System Image.
|
|
The disk size can be configured with the following value in
|
|
the kernelcmdline attribute:
|
|
|
|
* ramdisk_size=kbyte-value"
|
|
|
|
An image built with the above setup can be tested in QEMU as
|
|
follows:
|
|
|
|
.. code:: bash
|
|
|
|
$ qemu -cdrom {exc_image_base_name}.x86_64-{exc_image_version}.install.iso
|
|
|
|
.. note:: Enough Main Memory
|
|
|
|
The machine, no matter if it's a virtual machine like QEMU
|
|
or a real machine, must provide enough RAM to hold the image
|
|
in the ramdisk as well as have enough RAM available to operate
|
|
the OS and its applications. The {kiwi} build image with the
|
|
extension .raw provides the System Image which gets deployed
|
|
into the RAM space. Substract the size of the System Image
|
|
from the RAM space the machine offers and make sure the result
|
|
is still big enough for the use case of the appliance. In
|
|
case of a virtual machine, attach enough main memory to fit
|
|
this calculation. In case of QEMU this can be done with
|
|
the `-m` option
|
|
|
|
Like all other oem {kiwi} images, also the ramdisk setup supports
|
|
all the deployments methods as explained in :ref:`deployment_methods`
|
|
This means it's also possible to dump the ISO image on a USB
|
|
stick let the system boot from it and unplug the stick from
|
|
the machine because the system was deployed into RAM
|
|
|
|
.. note:: Limitations Of RamDisk Deployments
|
|
|
|
Only standard images which can be booted by a simple root mount
|
|
and root switch can be used. Usually {kiwi} calls kexec after deployment
|
|
such that the correct, for the image created dracut initrd, will boot
|
|
the image. In case of a RAM only system kexec does not work because
|
|
it would loose the ramdisk contents. Thus the dracut initrd driving
|
|
the deployment is also the environment to boot the system.
|
|
There are cases where this environment is not suitable to boot
|
|
the system.
|