@@ -83,5 +83,6 @@ Documentation for filesystem implementations.
overlayfs
proc
qnx6
+ ramfs-rootfs-initramfs
virtiofs
vfat
similarity index 91%
rename from Documentation/filesystems/ramfs-rootfs-initramfs.txt
rename to Documentation/filesystems/ramfs-rootfs-initramfs.rst
@@ -1,5 +1,11 @@
-ramfs, rootfs and initramfs
+.. SPDX-License-Identifier: GPL-2.0
+
+===========================
+Ramfs, rootfs and initramfs
+===========================
+
October 17, 2005
+
Rob Landley <rob@landley.net>
=============================
@@ -99,14 +105,14 @@ out of that.
All this differs from the old initrd in several ways:
- The old initrd was always a separate file, while the initramfs archive is
- linked into the linux kernel image. (The directory linux-*/usr is devoted
- to generating this archive during the build.)
+ linked into the linux kernel image. (The directory ``linux-*/usr`` is
+ devoted to generating this archive during the build.)
- The old initrd file was a gzipped filesystem image (in some file format,
such as ext2, that needed a driver built into the kernel), while the new
initramfs archive is a gzipped cpio archive (like tar only simpler,
- see cpio(1) and Documentation/driver-api/early-userspace/buffer-format.rst). The
- kernel's cpio extraction code is not only extremely small, it's also
+ see cpio(1) and Documentation/driver-api/early-userspace/buffer-format.rst).
+ The kernel's cpio extraction code is not only extremely small, it's also
__init text and data that can be discarded during the boot process.
- The program run by the old initrd (which was called /initrd, not /init) did
@@ -139,7 +145,7 @@ and living in usr/Kconfig) can be used to specify a source for the
initramfs archive, which will automatically be incorporated into the
resulting binary. This option can point to an existing gzipped cpio
archive, a directory containing files to be archived, or a text file
-specification such as the following example:
+specification such as the following example::
dir /dev 755 0 0
nod /dev/console 644 0 0 c 5 1
@@ -175,12 +181,12 @@ or extracting your own preprepared cpio files to feed to the kernel build
(instead of a config file or directory).
The following command line can extract a cpio image (either by the above script
-or by the kernel build) back into its component files:
+or by the kernel build) back into its component files::
cpio -i -d -H newc -F initramfs_data.cpio --no-absolute-filenames
The following shell script can create a prebuilt cpio archive you can
-use in place of the above config file:
+use in place of the above config file::
#!/bin/sh
@@ -202,14 +208,17 @@ use in place of the above config file:
exit 1
fi
-Note: The cpio man page contains some bad advice that will break your initramfs
-archive if you follow it. It says "A typical way to generate the list
-of filenames is with the find command; you should give find the -depth option
-to minimize problems with permissions on directories that are unwritable or not
-searchable." Don't do this when creating initramfs.cpio.gz images, it won't
-work. The Linux kernel cpio extractor won't create files in a directory that
-doesn't exist, so the directory entries must go before the files that go in
-those directories. The above script gets them in the right order.
+.. Note::
+
+ The cpio man page contains some bad advice that will break your initramfs
+ archive if you follow it. It says "A typical way to generate the list
+ of filenames is with the find command; you should give find the -depth
+ option to minimize problems with permissions on directories that are
+ unwritable or not searchable." Don't do this when creating
+ initramfs.cpio.gz images, it won't work. The Linux kernel cpio extractor
+ won't create files in a directory that doesn't exist, so the directory
+ entries must go before the files that go in those directories.
+ The above script gets them in the right order.
External initramfs images:
--------------------------
@@ -236,9 +245,10 @@ An initramfs archive is a complete self-contained root filesystem for Linux.
If you don't already understand what shared libraries, devices, and paths
you need to get a minimal root filesystem up and running, here are some
references:
-http://www.tldp.org/HOWTO/Bootdisk-HOWTO/
-http://www.tldp.org/HOWTO/From-PowerUp-To-Bash-Prompt-HOWTO.html
-http://www.linuxfromscratch.org/lfs/view/stable/
+
+- http://www.tldp.org/HOWTO/Bootdisk-HOWTO/
+- http://www.tldp.org/HOWTO/From-PowerUp-To-Bash-Prompt-HOWTO.html
+- http://www.linuxfromscratch.org/lfs/view/stable/
The "klibc" package (http://www.kernel.org/pub/linux/libs/klibc) is
designed to be a tiny C library to statically link early userspace
@@ -255,7 +265,7 @@ name lookups, even when otherwise statically linked.)
A good first step is to get initramfs to run a statically linked "hello world"
program as init, and test it under an emulator like qemu (www.qemu.org) or
-User Mode Linux, like so:
+User Mode Linux, like so::
cat > hello.c << EOF
#include <stdio.h>
@@ -326,8 +336,8 @@ the above threads) is:
explained his reasoning:
- http://www.uwsg.iu.edu/hypermail/linux/kernel/0112.2/1550.html
- http://www.uwsg.iu.edu/hypermail/linux/kernel/0112.2/1638.html
+ - http://www.uwsg.iu.edu/hypermail/linux/kernel/0112.2/1550.html
+ - http://www.uwsg.iu.edu/hypermail/linux/kernel/0112.2/1638.html
and, most importantly, designed and implemented the initramfs code.
- Add a SPDX header; - Add a document title; - Some whitespace fixes and new line breaks; - Mark literal blocks as such; - Add table markups; - Use notes markups; - Add lists markups; - Add it to filesystems/index.rst. Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org> --- Documentation/filesystems/index.rst | 1 + ...itramfs.txt => ramfs-rootfs-initramfs.rst} | 54 +++++++++++-------- 2 files changed, 33 insertions(+), 22 deletions(-) rename Documentation/filesystems/{ramfs-rootfs-initramfs.txt => ramfs-rootfs-initramfs.rst} (91%)