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-rw-r--r--documentation/ref-manual/terms.rst42
-rw-r--r--documentation/ref-manual/variables.rst42
2 files changed, 42 insertions, 42 deletions
diff --git a/documentation/ref-manual/terms.rst b/documentation/ref-manual/terms.rst
index 92cc723ff6..68313d0294 100644
--- a/documentation/ref-manual/terms.rst
+++ b/documentation/ref-manual/terms.rst
@@ -212,6 +212,48 @@ universal, the list includes them just in case:
212 of the supported image types that the Yocto Project provides, see the 212 of the supported image types that the Yocto Project provides, see the
213 ":ref:`ref-manual/images:Images`" chapter. 213 ":ref:`ref-manual/images:Images`" chapter.
214 214
215 :term:`Initramfs`
216 An Initial RAM Filesystem (:term:`Initramfs`) is an optionally compressed
217 :wikipedia:`cpio <Cpio>` archive which is extracted
218 by the Linux kernel into RAM in a special :wikipedia:`tmpfs <Tmpfs>`
219 instance, used as the initial root filesystem.
220
221 This is a replacement for the legacy init RAM disk ("initrd")
222 technique, booting on an emulated block device in RAM, but being less
223 efficient because of the overhead of going through a filesystem and
224 having to duplicate accessed file contents in the file cache in RAM,
225 as for any block device.
226
227 .. note:
228
229 As far as bootloaders are concerned, :term:`Initramfs` and "initrd"
230 images are still copied to RAM in the same way. That's why most
231 most bootloaders refer to :term:`Initramfs` images as "initrd"
232 or "init RAM disk".
233
234 This kind of mechanism is typically used for two reasons:
235
236 - For booting the same kernel binary on multiple systems requiring
237 different device drivers. The :term:`Initramfs` image is then customized
238 for each type of system, to include the specific kernel modules
239 necessary to access the final root filesystem. This technique
240 is used on all GNU / Linux distributions for desktops and servers.
241
242 - For booting faster. As the root filesystem is extracted into RAM,
243 accessing the first user-space applications is very fast, compared
244 to having to initialize a block device, to access multiple blocks
245 from it, and to go through a filesystem having its own overhead.
246 For example, this allows to display a splashscreen very early,
247 and to later take care of mounting the final root filesystem and
248 loading less time-critical kernel drivers.
249
250 This cpio archive can either be loaded to RAM by the bootloader,
251 or be included in the kernel binary.
252
253 For information on creating and using an :term:`Initramfs`, see the
254 ":ref:`dev-manual/building:building an initial ram filesystem (Initramfs) image`"
255 section in the Yocto Project Development Tasks Manual.
256
215 :term:`Layer` 257 :term:`Layer`
216 A collection of related recipes. Layers allow you to consolidate related 258 A collection of related recipes. Layers allow you to consolidate related
217 metadata to customize your build. Layers also isolate information used 259 metadata to customize your build. Layers also isolate information used
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