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manuals: improve initramfs details
- Create a new entry in the glossary - Add implementation details - Replace the mention of "init ramdisk" by "initramfs¨ whenever possible - Remove obsolete and duplicate information - Fix spacing issues in the Sphinx code (From yocto-docs rev: 952c7e6dee49532705b2c162f4728e635c38df3f) Signed-off-by: Michael Opdenacker <michael.opdenacker@bootlin.com> Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
This commit is contained in:
Michael Opdenacker
Richard Purdie
parent
c3c7344826
commit
9dbd27a48a
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@ -3882,99 +3882,59 @@ and have separate configuration files, BitBake places the artifacts for
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each build in the respective temporary build directories (i.e.
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:term:`TMPDIR`).
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Building an Initial RAM Filesystem (initramfs) Image
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Building an Initial RAM Filesystem (Initramfs) Image
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----------------------------------------------------
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An initial RAM filesystem (initramfs) image provides a temporary root
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filesystem used for early system initialization (e.g. loading of modules
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needed to locate and mount the "real" root filesystem).
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An initial RAM filesystem (:term:`Initramfs`) image provides a temporary root
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filesystem used for early system initialization, typically providing tools and
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loading modules needed to locate and mount the final root filesystem.
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.. note::
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Follow these steps to create an :term:`Initramfs` image:
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The initramfs image is the successor of initial RAM disk (initrd). It
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is a "copy in and out" (cpio) archive of the initial filesystem that
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gets loaded into memory during the Linux startup process. Because
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Linux uses the contents of the archive during initialization, the
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initramfs image needs to contain all of the device drivers and tools
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needed to mount the final root filesystem.
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Follow these steps to create an initramfs image:
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1. *Create the initramfs Image Recipe:* You can reference the
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1. *Create the Initramfs Image Recipe:* You can reference the
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``core-image-minimal-initramfs.bb`` recipe found in the
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``meta/recipes-core`` directory of the :term:`Source Directory`
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as an example
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from which to work.
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as an example from which to work.
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2. *Decide if You Need to Bundle the initramfs Image Into the Kernel
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Image:* If you want the initramfs image that is built to be bundled
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in with the kernel image, set the
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:term:`INITRAMFS_IMAGE_BUNDLE`
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variable to "1" in your ``local.conf`` configuration file and set the
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:term:`INITRAMFS_IMAGE`
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variable in the recipe that builds the kernel image.
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2. *Decide if You Need to Bundle the Initramfs Image Into the Kernel
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Image:* If you want the :term:`Initramfs` image that is built to be bundled
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in with the kernel image, set the :term:`INITRAMFS_IMAGE_BUNDLE`
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variable to ``"1"`` in your ``local.conf`` configuration file and set the
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:term:`INITRAMFS_IMAGE` variable in the recipe that builds the kernel image.
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.. note::
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It is recommended that you bundle the initramfs image with the
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kernel image to avoid circular dependencies between the kernel
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recipe and the initramfs recipe should the initramfs image include
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kernel modules.
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Setting the :term:`INITRAMFS_IMAGE_BUNDLE` flag causes the initramfs
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Setting the :term:`INITRAMFS_IMAGE_BUNDLE` flag causes the :term:`Initramfs`
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image to be unpacked into the ``${B}/usr/`` directory. The unpacked
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initramfs image is then passed to the kernel's ``Makefile`` using the
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:term:`CONFIG_INITRAMFS_SOURCE`
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variable, allowing the initramfs image to be built into the kernel
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normally.
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:term:`Initramfs` image is then passed to the kernel's ``Makefile`` using the
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:term:`CONFIG_INITRAMFS_SOURCE` variable, allowing the :term:`Initramfs`
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image to be built into the kernel normally.
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.. note::
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3. *Optionally Add Items to the Initramfs Image Through the Initramfs
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Image Recipe:* If you add items to the :term:`Initramfs` image by way of its
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recipe, you should use :term:`PACKAGE_INSTALL` rather than
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:term:`IMAGE_INSTALL`. :term:`PACKAGE_INSTALL` gives more direct control of
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what is added to the image as compared to the defaults you might not
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necessarily want that are set by the :ref:`image <ref-classes-image>`
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or :ref:`core-image <ref-classes-core-image>` classes.
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Bundling the initramfs with the kernel conflates the code in the initramfs
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with the GPLv2 licensed Linux kernel binary. Thus only GPLv2 compatible
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software may be part of a bundled initramfs.
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.. note::
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If you choose to not bundle the initramfs image with the kernel
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image, you are essentially using an
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`Initial RAM Disk (initrd) <https://en.wikipedia.org/wiki/Initrd>`__.
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Creating an initrd is handled primarily through the :term:`INITRD_IMAGE`,
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``INITRD_LIVE``, and ``INITRD_IMAGE_LIVE`` variables. For more
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information, see the :ref:`ref-classes-image-live` file.
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3. *Optionally Add Items to the initramfs Image Through the initramfs
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Image Recipe:* If you add items to the initramfs image by way of its
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recipe, you should use
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:term:`PACKAGE_INSTALL`
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rather than
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:term:`IMAGE_INSTALL`.
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:term:`PACKAGE_INSTALL` gives more direct control of what is added to the
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image as compared to the defaults you might not necessarily want that
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are set by the :ref:`image <ref-classes-image>`
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or :ref:`core-image <ref-classes-core-image>`
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classes.
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4. *Build the Kernel Image and the initramfs Image:* Build your kernel
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image using BitBake. Because the initramfs image recipe is a
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dependency of the kernel image, the initramfs image is built as well
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4. *Build the Kernel Image and the Initramfs Image:* Build your kernel
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image using BitBake. Because the :term:`Initramfs` image recipe is a
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dependency of the kernel image, the :term:`Initramfs` image is built as well
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and bundled with the kernel image if you used the
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:term:`INITRAMFS_IMAGE_BUNDLE`
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variable described earlier.
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:term:`INITRAMFS_IMAGE_BUNDLE` variable described earlier.
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Bundling an Initramfs Image From a Separate Multiconfig
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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There may be a case where we want to build an initramfs image which does not
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There may be a case where we want to build an :term:`Initramfs` image which does not
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inherit the same distro policy as our main image, for example, we may want
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our main image to use ``TCLIBC="glibc"``, but to use ``TCLIBC="musl"`` in our initramfs
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our main image to use ``TCLIBC="glibc"``, but to use ``TCLIBC="musl"`` in our :term:`Initramfs`
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image to keep a smaller footprint. However, by performing the steps mentioned
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above the initramfs image will inherit ``TCLIBC="glibc"`` without allowing us
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above the :term:`Initramfs` image will inherit ``TCLIBC="glibc"`` without allowing us
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to override it.
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To achieve this, you need to perform some additional steps:
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1. *Create a multiconfig for your initramfs image:* You can perform the steps
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1. *Create a multiconfig for your Initramfs image:* You can perform the steps
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on ":ref:`dev-manual/common-tasks:building images for multiple targets using multiple configurations`" to create a separate multiconfig.
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For the sake of simplicity let's assume such multiconfig is called: ``initramfscfg.conf`` and
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contains the variables::
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@ -3982,7 +3942,7 @@ To achieve this, you need to perform some additional steps:
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TMPDIR="${TOPDIR}/tmp-initramfscfg"
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TCLIBC="musl"
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2. *Set additional initramfs variables on your main configuration:*
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2. *Set additional Initramfs variables on your main configuration:*
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Additionally, on your main configuration (``local.conf``) you need to set the
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variables::
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@ -3997,7 +3957,7 @@ To achieve this, you need to perform some additional steps:
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Building a system with such configuration will build the kernel using the
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main configuration but the ``do_bundle_initramfs`` task will grab the
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selected :term:`INITRAMFS_IMAGE` from :term:`INITRAMFS_DEPLOY_DIR_IMAGE`
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instead, resulting in a musl based initramfs image bundled in the kernel
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instead, resulting in a musl based :term:`Initramfs` image bundled in the kernel
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but a glibc based main image.
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The same is applicable to avoid inheriting :term:`DISTRO_FEATURES` on :term:`INITRAMFS_IMAGE`
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@ -4171,7 +4131,7 @@ file::
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Finally, you should consider exactly the type of root filesystem you
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need to meet your needs while also reducing its size. For example,
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consider ``cramfs``, ``squashfs``, ``ubifs``, ``ext2``, or an
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``initramfs`` using ``initramfs``. Be aware that ``ext3`` requires a 1
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:term:`Initramfs` using ``initramfs``. Be aware that ``ext3`` requires a 1
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Mbyte journal. If you are okay with running read-only, you do not need
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this journal.
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@ -8802,7 +8762,7 @@ perform a one-time setup of your controller image by doing the following:
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- Installs normal linux utilities not BusyBox ones (e.g. ``bash``,
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``coreutils``, ``tar``, ``gzip``, and ``kmod``).
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- Uses a custom Initial RAM Disk (initramfs) image with a custom
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- Uses a custom :term:`Initramfs` image with a custom
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installer. A normal image that you can install usually creates a
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single root filesystem partition. This image uses another installer that
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creates a specific partition layout. Not all Board Support
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@ -123,9 +123,9 @@ available. Follow these general steps to run QEMU:
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$ runqemu qemux86-64 core-image-minimal ext4
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- This example specifies to boot an initial RAM disk image and to
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enable audio in QEMU. For this case, ``runqemu`` set the internal
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variable ``FSTYPE`` to "cpio.gz". Also, for audio to be enabled,
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- This example specifies to boot an :term:`Initramfs` image and to
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enable audio in QEMU. For this case, ``runqemu`` sets the internal
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variable ``FSTYPE`` to ``cpio.gz``. Also, for audio to be enabled,
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an appropriate driver must be installed (see the previous
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description for the ``audio`` option for more information).
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::
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@ -394,7 +394,7 @@ command line:
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options are basically identical. If you do not provide a MACHINE
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option, ``runqemu`` tries to determine it based on other options.
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- ``ramfs``: Indicates you are booting an initial RAM disk (initramfs)
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- ``ramfs``: Indicates you are booting an :term:`Initramfs`
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image, which means the ``FSTYPE`` is ``cpio.gz``.
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- ``iso``: Indicates you are booting an ISO image, which means the
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@ -54,7 +54,7 @@ occurred:
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when "pam" is in :term:`DISTRO_FEATURES`.
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- The ``switch_root`` program is now packaged in a separate
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"util-linux-switch-root" package for small initramfs images that
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"util-linux-switch-root" package for small :term:`Initramfs` images that
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do not need the whole ``util-linux`` package or the busybox
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binary, which are both much larger than ``switch_root``. The main
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``util-linux`` package has a recommended runtime dependency (i.e.
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@ -265,10 +265,10 @@ using the GL options.
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.. _migration-3.2-initramfs-suffix:
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initramfs images now use a blank suffix
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Initramfs images now use a blank suffix
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---------------------------------------
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The reference initramfs images (``core-image-minimal-initramfs``,
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The reference :term:`Initramfs` images (``core-image-minimal-initramfs``,
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``core-image-tiny-initramfs`` and ``core-image-testmaster-initramfs``) now
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set an empty string for :term:`IMAGE_NAME_SUFFIX`, which otherwise defaults
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to ``".rootfs"``. These images aren't root filesystems and thus the rootfs
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@ -36,7 +36,7 @@ New Features / Enhancements in 3.4
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- Kernel-related enhancements:
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- Support zstd-compressed modules and initramfs images
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- Support zstd-compressed modules and :term:`Initramfs` images
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- Allow opt-out of split kernel modules
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- linux-yocto-dev: base AUTOREV on specified version
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- kernel-yocto: provide debug / summary information for metadata
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@ -211,7 +211,7 @@ The following corrections have been made to the LICENSE values set by recipes:
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Other license-related notes:
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- When creating recipes for Python software, recipetool will now treat "BSD" as "BSD-3-Clause" for the purposes of setting LICENSE, as that is the most common understanding.
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- Please be aware that an initramfs bundled with the kernel using :term:`INITRAMFS_IMAGE_BUNDLE` should only contain GPLv2-compatible software; this is now mentioned in the documentation.
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- Please be aware that an :term:`Initramfs` bundled with the kernel using :term:`INITRAMFS_IMAGE_BUNDLE` should only contain GPLv2-compatible software; this is now mentioned in the documentation.
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Security Fixes in 3.4
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~~~~~~~~~~~~~~~~~~~~~
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@ -30,7 +30,7 @@ New Features / Enhancements in 4.0
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- New :ref:`overlayfs <ref-classes-overlayfs>` and
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:ref:`overlayfs-etc <ref-classes-overlayfs-etc>` classes and
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``overlayroot`` support in the initramfs framework to make it easier to
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``overlayroot`` support in the :term:`Initramfs` framework to make it easier to
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overlay read-only filesystems (for example) with
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`OverlayFS <https://en.wikipedia.org/wiki/OverlayFS>`__.
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@ -168,7 +168,7 @@ New Features / Enhancements in 4.0
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- Kernel-related enhancements:
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- Allow initramfs to be built from a separate multiconfig
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- Allow :term:`Initramfs` to be built from a separate multiconfig
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- Make kernel-base recommend kernel-image, not depend (allowing images containing kernel modules without kernel image)
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- linux-yocto: split vtpm for more granular inclusion
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- linux-yocto: cfg/debug: add configs for kcsan
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@ -182,7 +182,7 @@ New Features / Enhancements in 4.0
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- FIT image related enhancements:
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- New ``FIT_SUPPORTED_INITRAMFS_FSTYPES`` variable to allow extending initramfs image types to look for
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- New ``FIT_SUPPORTED_INITRAMFS_FSTYPES`` variable to allow extending :term:`Initramfs` image types to look for
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- New ``FIT_CONF_PREFIX`` variable to allow overriding FIT configuration prefix
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- Use 'bbnote' for better logging
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@ -276,7 +276,7 @@ New Features / Enhancements in 4.0
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- volatile-binds: SELinux and overlayfs extensions in mount-copybind
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- gtk-icon-cache: Allow using gtk4
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- kmod: Add an exclude directive to depmod
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- os-release: add os-release-initrd package for use in systemd-based initramfs images
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- os-release: add os-release-initrd package for use in systemd-based :term:`Initramfs` images
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- gstreamer1.0-plugins-base: add support for graphene
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- gpg-sign: Add parameters to gpg signature function
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- package_manager: sign DEB package feeds
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@ -1256,9 +1256,9 @@ package installs all packages with modules and various other kernel
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packages such as ``kernel-vmlinux``.
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The ``kernel`` class contains logic that allows you to embed an initial
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RAM filesystem (initramfs) image when you build the kernel image. For
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information on how to build an initramfs, see the
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":ref:`dev-manual/common-tasks:building an initial ram filesystem (initramfs) image`" section in
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RAM filesystem (:term:`Initramfs`) image when you build the kernel image. For
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information on how to build an :term:`Initramfs`, see the
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":ref:`dev-manual/common-tasks:building an initial ram filesystem (Initramfs) image`" section in
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the Yocto Project Development Tasks Manual.
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Various other classes are used by the ``kernel`` and ``module`` classes
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@ -78,11 +78,11 @@ Following is a list of supported recipes:
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libraries you can use in a host development environment.
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- ``core-image-minimal-initramfs``: A ``core-image-minimal`` image that
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has the Minimal RAM-based Initial Root Filesystem (initramfs) as part
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has the Minimal RAM-based Initial Root Filesystem (:term:`Initramfs`) as part
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of the kernel, which allows the system to find the first "init"
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program more efficiently. See the
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:term:`PACKAGE_INSTALL` variable for
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additional information helpful when working with initramfs images.
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additional information helpful when working with :term:`Initramfs` images.
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- ``core-image-minimal-mtdutils``: A ``core-image-minimal`` image that
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has support for the Minimal MTD Utilities, which let the user
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@ -121,7 +121,7 @@ Following is a list of supported recipes:
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section in the Yocto Project Development Tasks Manual.
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- ``core-image-testmaster-initramfs``: A RAM-based Initial Root
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Filesystem (initramfs) image tailored for use with the
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Filesystem (:term:`Initramfs`) image tailored for use with the
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``core-image-testmaster`` image.
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- ``core-image-weston``: A very basic Wayland image with a terminal.
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@ -575,10 +575,8 @@ information on live image types.
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``do_bundle_initramfs``
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-----------------------
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Combines an initial RAM disk (initramfs) image and kernel together to
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form a single image. The
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:term:`CONFIG_INITRAMFS_SOURCE` variable
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has some more information about these types of images.
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Combines an :term:`Initramfs` image and kernel together to
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form a single image.
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.. _ref-tasks-rootfs:
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@ -1242,24 +1242,24 @@ system and gives an overview of their function and contents.
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:term:`Source Directory`.
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:term:`CONFIG_INITRAMFS_SOURCE`
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Identifies the initial RAM filesystem (initramfs) source files. The
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Identifies the initial RAM filesystem (:term:`Initramfs`) source files. The
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OpenEmbedded build system receives and uses this kernel Kconfig
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variable as an environment variable. By default, the variable is set
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to null ("").
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The :term:`CONFIG_INITRAMFS_SOURCE` can be either a single cpio archive
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with a ``.cpio`` suffix or a space-separated list of directories and
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files for building the initramfs image. A cpio archive should contain
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a filesystem archive to be used as an initramfs image. Directories
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should contain a filesystem layout to be included in the initramfs
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files for building the :term:`Initramfs` image. A cpio archive should contain
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a filesystem archive to be used as an :term:`Initramfs` image. Directories
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should contain a filesystem layout to be included in the :term:`Initramfs`
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image. Files should contain entries according to the format described
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by the ``usr/gen_init_cpio`` program in the kernel tree.
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If you specify multiple directories and files, the initramfs image
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If you specify multiple directories and files, the :term:`Initramfs` image
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will be the aggregate of all of them.
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For information on creating an initramfs, see the
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":ref:`dev-manual/common-tasks:building an initial ram filesystem (initramfs) image`" section
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For information on creating an :term:`Initramfs`, see the
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":ref:`dev-manual/common-tasks:building an initial ram filesystem (Initramfs) image`" section
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in the Yocto Project Development Tasks Manual.
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:term:`CONFIG_SITE`
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@ -3182,10 +3182,10 @@ system and gives an overview of their function and contents.
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image, do not use the :term:`IMAGE_INSTALL` variable to specify
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packages for installation. Instead, use the
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:term:`PACKAGE_INSTALL` variable, which
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allows the initial RAM filesystem (initramfs) recipe to use a
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allows the initial RAM filesystem (:term:`Initramfs`) recipe to use a
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fixed set of packages and not be affected by :term:`IMAGE_INSTALL`.
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For information on creating an initramfs, see the
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":ref:`dev-manual/common-tasks:building an initial ram filesystem (initramfs) image`"
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For information on creating an :term:`Initramfs`, see the
|
||||
":ref:`dev-manual/common-tasks:building an initial ram filesystem (Initramfs) image`"
|
||||
section in the Yocto Project Development Tasks Manual.
|
||||
|
||||
- Using :term:`IMAGE_INSTALL` with the
|
||||
|
|
@ -3265,7 +3265,7 @@ system and gives an overview of their function and contents.
|
|||
to distinguish the image file from other files created during image
|
||||
building; however if this suffix is redundant or not desired you can
|
||||
clear the value of this variable (set the value to ""). For example,
|
||||
this is typically cleared in initramfs image recipes.
|
||||
this is typically cleared in :term:`Initramfs` image recipes.
|
||||
|
||||
:term:`IMAGE_OVERHEAD_FACTOR`
|
||||
Defines a multiplier that the build system applies to the initial
|
||||
|
|
@ -3632,37 +3632,79 @@ system and gives an overview of their function and contents.
|
|||
even if the toolchain's binaries are strippable, there are other files
|
||||
needed for the build that are not strippable.
|
||||
|
||||
:term:`Initramfs`
|
||||
An Initial RAM Filesystem (:term:`Initramfs`) is an optionally compressed
|
||||
`cpio <https://en.wikipedia.org/wiki/Cpio>`__ archive which is extracted
|
||||
by the Linux kernel into RAM in a special `tmpfs <https://en.wikipedia.org/wiki/Tmpfs>`__
|
||||
instance, used as the initial root filesystem.
|
||||
|
||||
This is a replacement for the legacy init RAM disk ("initrd")
|
||||
technique, booting on an emulated block device in RAM, but being less
|
||||
efficient because of the overhead of going through a filesystem and
|
||||
having to duplicate accessed file contents in the file cache in RAM,
|
||||
as for any block device.
|
||||
|
||||
.. note:
|
||||
|
||||
As far as bootloaders are concerned, :term:`Initramfs` and "initrd"
|
||||
images are still copied to RAM in the same way. That's why most
|
||||
most bootloaders refer to :term:`Initramfs` images as "initrd"
|
||||
or "init RAM disk".
|
||||
|
||||
This kind of mechanism is typically used for two reasons:
|
||||
|
||||
- For booting the same kernel binary on multiple systems requiring
|
||||
different device drivers. The Initramfs image is then customized
|
||||
for each type of system, to include the specific kernel modules
|
||||
necessary to access the final root filesystem. This technique
|
||||
is used on all GNU / Linux distributions for desktops and servers.
|
||||
|
||||
- For booting faster. As the root filesystem is extracted into RAM,
|
||||
accessing the first user-space applications is very fast, compared
|
||||
to having to initialize a block device, to access multiple blocks
|
||||
from it, and to go through a filesystem having its own overhead.
|
||||
For example, this allows to display a splashscreen very early,
|
||||
and to later take care of mounting the final root filesystem and
|
||||
loading less time-critical kernel drivers.
|
||||
|
||||
This cpio archive can either be loaded to RAM by the bootloader,
|
||||
or be included in the kernel binary.
|
||||
|
||||
For information on creating and using an :term:`Initramfs`, see the
|
||||
":ref:`dev-manual/common-tasks:building an initial ram filesystem (Initramfs) image`"
|
||||
section in the Yocto Project Development Tasks Manual.
|
||||
|
||||
:term:`INITRAMFS_DEPLOY_DIR_IMAGE`
|
||||
Indicates the deploy directory used by ``do_bundle_initramfs`` where the
|
||||
:term:`INITRAMFS_IMAGE` will be fetched from.
|
||||
This variable is set by default to ``${DEPLOY_DIR_IMAGE}`` in the
|
||||
:ref:`kernel <ref-classes-kernel>` class and it's only meant to be changed
|
||||
when building an initramfs image from a separate multiconfig via :term:`INITRAMFS_MULTICONFIG`.
|
||||
when building an :term:`Initramfs` image from a separate multiconfig via :term:`INITRAMFS_MULTICONFIG`.
|
||||
|
||||
:term:`INITRAMFS_FSTYPES`
|
||||
Defines the format for the output image of an initial RAM filesystem
|
||||
(initramfs), which is used during boot. Supported formats are the
|
||||
(:term:`Initramfs`), which is used during boot. Supported formats are the
|
||||
same as those supported by the
|
||||
:term:`IMAGE_FSTYPES` variable.
|
||||
|
||||
The default value of this variable, which is set in the
|
||||
``meta/conf/bitbake.conf`` configuration file in the
|
||||
:term:`Source Directory`, is "cpio.gz". The Linux kernel's
|
||||
initramfs mechanism, as opposed to the initial RAM filesystem
|
||||
:term:`Initramfs` mechanism, as opposed to the initial RAM filesystem
|
||||
`initrd <https://en.wikipedia.org/wiki/Initrd>`__ mechanism, expects
|
||||
an optionally compressed cpio archive.
|
||||
|
||||
:term:`INITRAMFS_IMAGE`
|
||||
Specifies the :term:`PROVIDES` name of an image
|
||||
recipe that is used to build an initial RAM filesystem (initramfs)
|
||||
recipe that is used to build an initial RAM filesystem (:term:`Initramfs`)
|
||||
image. In other words, the :term:`INITRAMFS_IMAGE` variable causes an
|
||||
additional recipe to be built as a dependency to whatever root
|
||||
filesystem recipe you might be using (e.g. ``core-image-sato``). The
|
||||
initramfs image recipe you provide should set
|
||||
:term:`Initramfs` image recipe you provide should set
|
||||
:term:`IMAGE_FSTYPES` to
|
||||
:term:`INITRAMFS_FSTYPES`.
|
||||
|
||||
An initramfs image provides a temporary root filesystem used for
|
||||
An :term:`Initramfs` image provides a temporary root filesystem used for
|
||||
early system initialization (e.g. loading of modules needed to locate
|
||||
and mount the "real" root filesystem).
|
||||
|
||||
|
|
@ -3670,8 +3712,8 @@ system and gives an overview of their function and contents.
|
|||
|
||||
See the ``meta/recipes-core/images/core-image-minimal-initramfs.bb``
|
||||
recipe in the :term:`Source Directory`
|
||||
for an example initramfs recipe. To select this sample recipe as
|
||||
the one built to provide the initramfs image, set :term:`INITRAMFS_IMAGE`
|
||||
for an example :term:`Initramfs` recipe. To select this sample recipe as
|
||||
the one built to provide the :term:`Initramfs` image, set :term:`INITRAMFS_IMAGE`
|
||||
to "core-image-minimal-initramfs".
|
||||
|
||||
You can also find more information by referencing the
|
||||
|
|
@ -3681,13 +3723,13 @@ system and gives an overview of their function and contents.
|
|||
class to see how to use the :term:`INITRAMFS_IMAGE` variable.
|
||||
|
||||
If :term:`INITRAMFS_IMAGE` is empty, which is the default, then no
|
||||
initramfs image is built.
|
||||
:term:`Initramfs` image is built.
|
||||
|
||||
For more information, you can also see the
|
||||
:term:`INITRAMFS_IMAGE_BUNDLE`
|
||||
variable, which allows the generated image to be bundled inside the
|
||||
kernel image. Additionally, for information on creating an initramfs
|
||||
image, see the ":ref:`dev-manual/common-tasks:building an initial ram filesystem (initramfs) image`" section
|
||||
kernel image. Additionally, for information on creating an :term:`Initramfs`
|
||||
image, see the ":ref:`dev-manual/common-tasks:building an initial ram filesystem (Initramfs) image`" section
|
||||
in the Yocto Project Development Tasks Manual.
|
||||
|
||||
:term:`INITRAMFS_IMAGE_BUNDLE`
|
||||
|
|
@ -3696,32 +3738,32 @@ system and gives an overview of their function and contents.
|
|||
extra pass
|
||||
(:ref:`ref-tasks-bundle_initramfs`) during
|
||||
kernel compilation in order to build a single binary that contains
|
||||
both the kernel image and the initial RAM filesystem (initramfs)
|
||||
both the kernel image and the initial RAM filesystem (:term:`Initramfs`)
|
||||
image. This makes use of the
|
||||
:term:`CONFIG_INITRAMFS_SOURCE` kernel
|
||||
feature.
|
||||
|
||||
.. note::
|
||||
|
||||
Bundling the initramfs with the kernel conflates the code in the
|
||||
initramfs with the GPLv2 licensed Linux kernel binary. Thus only GPLv2
|
||||
compatible software may be part of a bundled initramfs.
|
||||
Bundling the :term:`Initramfs` with the kernel conflates the code in the
|
||||
:term:`Initramfs` with the GPLv2 licensed Linux kernel binary. Thus only GPLv2
|
||||
compatible software may be part of a bundled :term:`Initramfs`.
|
||||
|
||||
.. note::
|
||||
|
||||
Using an extra compilation pass to bundle the initramfs avoids a
|
||||
circular dependency between the kernel recipe and the initramfs
|
||||
recipe should the initramfs include kernel modules. Should that be
|
||||
the case, the initramfs recipe depends on the kernel for the
|
||||
kernel modules, and the kernel depends on the initramfs recipe
|
||||
since the initramfs is bundled inside the kernel image.
|
||||
Using an extra compilation pass to bundle the :term:`Initramfs` avoids a
|
||||
circular dependency between the kernel recipe and the :term:`Initramfs`
|
||||
recipe should the :term:`Initramfs` include kernel modules. Should that be
|
||||
the case, the :term:`Initramfs` recipe depends on the kernel for the
|
||||
kernel modules, and the kernel depends on the :term:`Initramfs` recipe
|
||||
since the :term:`Initramfs` is bundled inside the kernel image.
|
||||
|
||||
The combined binary is deposited into the ``tmp/deploy`` directory,
|
||||
which is part of the :term:`Build Directory`.
|
||||
|
||||
Setting the variable to "1" in a configuration file causes the
|
||||
OpenEmbedded build system to generate a kernel image with the
|
||||
initramfs specified in :term:`INITRAMFS_IMAGE` bundled within::
|
||||
:term:`Initramfs` specified in :term:`INITRAMFS_IMAGE` bundled within::
|
||||
|
||||
INITRAMFS_IMAGE_BUNDLE = "1"
|
||||
|
||||
|
|
@ -3739,7 +3781,7 @@ system and gives an overview of their function and contents.
|
|||
See the
|
||||
:yocto_git:`local.conf.sample.extended </poky/tree/meta-poky/conf/templates/default/local.conf.sample.extended>`
|
||||
file for additional information. Also, for information on creating an
|
||||
initramfs, see the ":ref:`dev-manual/common-tasks:building an initial ram filesystem (initramfs) image`" section
|
||||
:term:`Initramfs`, see the ":ref:`dev-manual/common-tasks:building an initial ram filesystem (Initramfs) image`" section
|
||||
in the Yocto Project Development Tasks Manual.
|
||||
|
||||
:term:`INITRAMFS_LINK_NAME`
|
||||
|
|
@ -3764,7 +3806,7 @@ system and gives an overview of their function and contents.
|
|||
This allows the kernel to bundle an :term:`INITRAMFS_IMAGE` coming from
|
||||
a separate multiconfig, this is meant to be used in addition to :term:`INITRAMFS_DEPLOY_DIR_IMAGE`.
|
||||
|
||||
For more information on how to bundle an initramfs image from a separate
|
||||
For more information on how to bundle an :term:`Initramfs` image from a separate
|
||||
multiconfig see the ":ref:`dev-manual/common-tasks:Bundling an Initramfs Image From a Separate Multiconfig`"
|
||||
section in the Yocto Project Development Tasks Manual.
|
||||
|
||||
|
|
@ -4240,7 +4282,7 @@ system and gives an overview of their function and contents.
|
|||
:term:`KERNELDEPMODDEPEND` does not control whether or not that data
|
||||
exists, but simply whether or not it is used. If you do not need to
|
||||
use the data, set the :term:`KERNELDEPMODDEPEND` variable in your
|
||||
``initramfs`` recipe. Setting the variable there when the data is not
|
||||
:term:`Initramfs` recipe. Setting the variable there when the data is not
|
||||
needed avoids a potential dependency loop.
|
||||
|
||||
:term:`KFEATURE_DESCRIPTION`
|
||||
|
|
@ -5395,9 +5437,9 @@ system and gives an overview of their function and contents.
|
|||
:term:`IMAGE_INSTALL` variable to specify
|
||||
packages for installation. The exception to this is when working with
|
||||
the :ref:`core-image-minimal-initramfs <ref-manual/images:images>`
|
||||
image. When working with an initial RAM filesystem (initramfs) image,
|
||||
image. When working with an initial RAM filesystem (:term:`Initramfs`) image,
|
||||
use the :term:`PACKAGE_INSTALL` variable. For information on creating an
|
||||
initramfs, see the ":ref:`dev-manual/common-tasks:building an initial ram filesystem (initramfs) image`" section
|
||||
:term:`Initramfs`, see the ":ref:`dev-manual/common-tasks:building an initial ram filesystem (Initramfs) image`" section
|
||||
in the Yocto Project Development Tasks Manual.
|
||||
|
||||
:term:`PACKAGE_INSTALL_ATTEMPTONLY`
|
||||
|
|
|
|||
Loading…
Reference in New Issue
Block a user