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Diffstat (limited to 'documentation/ref-manual/variables.rst')
-rw-r--r-- | documentation/ref-manual/variables.rst | 42 |
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diff --git a/documentation/ref-manual/variables.rst b/documentation/ref-manual/variables.rst index faa7c036e5..39d279874d 100644 --- a/documentation/ref-manual/variables.rst +++ b/documentation/ref-manual/variables.rst | |||
@@ -3956,48 +3956,6 @@ system and gives an overview of their function and contents. | |||
3956 | even if the toolchain's binaries are strippable, there are other files | 3956 | even if the toolchain's binaries are strippable, there are other files |
3957 | needed for the build that are not strippable. | 3957 | needed for the build that are not strippable. |
3958 | 3958 | ||
3959 | :term:`Initramfs` | ||
3960 | An Initial RAM Filesystem (:term:`Initramfs`) is an optionally compressed | ||
3961 | :wikipedia:`cpio <Cpio>` archive which is extracted | ||
3962 | by the Linux kernel into RAM in a special :wikipedia:`tmpfs <Tmpfs>` | ||
3963 | instance, used as the initial root filesystem. | ||
3964 | |||
3965 | This is a replacement for the legacy init RAM disk ("initrd") | ||
3966 | technique, booting on an emulated block device in RAM, but being less | ||
3967 | efficient because of the overhead of going through a filesystem and | ||
3968 | having to duplicate accessed file contents in the file cache in RAM, | ||
3969 | as for any block device. | ||
3970 | |||
3971 | .. note: | ||
3972 | |||
3973 | As far as bootloaders are concerned, :term:`Initramfs` and "initrd" | ||
3974 | images are still copied to RAM in the same way. That's why most | ||
3975 | most bootloaders refer to :term:`Initramfs` images as "initrd" | ||
3976 | or "init RAM disk". | ||
3977 | |||
3978 | This kind of mechanism is typically used for two reasons: | ||
3979 | |||
3980 | - For booting the same kernel binary on multiple systems requiring | ||
3981 | different device drivers. The :term:`Initramfs` image is then customized | ||
3982 | for each type of system, to include the specific kernel modules | ||
3983 | necessary to access the final root filesystem. This technique | ||
3984 | is used on all GNU / Linux distributions for desktops and servers. | ||
3985 | |||
3986 | - For booting faster. As the root filesystem is extracted into RAM, | ||
3987 | accessing the first user-space applications is very fast, compared | ||
3988 | to having to initialize a block device, to access multiple blocks | ||
3989 | from it, and to go through a filesystem having its own overhead. | ||
3990 | For example, this allows to display a splashscreen very early, | ||
3991 | and to later take care of mounting the final root filesystem and | ||
3992 | loading less time-critical kernel drivers. | ||
3993 | |||
3994 | This cpio archive can either be loaded to RAM by the bootloader, | ||
3995 | or be included in the kernel binary. | ||
3996 | |||
3997 | For information on creating and using an :term:`Initramfs`, see the | ||
3998 | ":ref:`dev-manual/building:building an initial ram filesystem (Initramfs) image`" | ||
3999 | section in the Yocto Project Development Tasks Manual. | ||
4000 | |||
4001 | :term:`INITRAMFS_DEPLOY_DIR_IMAGE` | 3959 | :term:`INITRAMFS_DEPLOY_DIR_IMAGE` |
4002 | Indicates the deploy directory used by :ref:`ref-tasks-bundle_initramfs` | 3960 | Indicates the deploy directory used by :ref:`ref-tasks-bundle_initramfs` |
4003 | where the :term:`INITRAMFS_IMAGE` will be fetched from. This variable is | 3961 | where the :term:`INITRAMFS_IMAGE` will be fetched from. This variable is |