c99983a91e
The installation chapter contained information about the manual install of package keys. That information is suspect to be always outdated because these keys changes. Instead of describing the manual install of the package key the docs moved to use the auto-import feature of the package manager. As the instructions were also rpm specific but we also support install via other package mangers the complete chapter was a bit reworked and should be more straight forward now. This Fixes #1799
88 lines
3.5 KiB
ReStructuredText
88 lines
3.5 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
|
|
|
|
$ sudo qemu -cdrom \
|
|
{exc_image_base_name}.x86_64-{exc_image_version}.install.iso \
|
|
-serial stdio
|
|
|
|
.. 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.
|