docs: ramdisk/initrd/initramfs corrections

initrd/initramfs/ramdisk docs: - fix typos/spellos/grammar - clarify RAM disk config location - correct cpio option Acked-by: Bryan O'Sullivan <bos@serpentine.com> Acked-by: Rob Landley <rob@landley.net> Cc: Werner Almesberger <werner@almesberger.net> Cc: H. Peter Anvin <hpa@zytor.com> Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com> Acked-by: Jesper Juhl <jesper.juhl@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

docs: ramdisk/initrd/initramfs corrections
initrd/initramfs/ramdisk docs: - fix typos/spellos/grammar - clarify RAM disk config location - correct cpio option Acked-by: Bryan O'Sullivan <bos@serpentine.com> Acked-by: Rob Landley <rob@landley.net> Cc: Werner Almesberger <werner@almesberger.net> Cc: H. Peter Anvin <hpa@zytor.com> Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com> Acked-by: Jesper Juhl <jesper.juhl@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Randy Dunlap · Linus Torvalds
1 parent 0e1ccb9619
Showing 4 changed files with 27 additions and 22 deletions Side-by-side Diff
Documentation/early-userspace/README
Documentation/filesystems/ramfs-rootfs-initramfs.txt
Documentation/initrd.txt
Documentation/ramdisk.txt
@@ -19,7 +19,7 @@
 - klibc, a userspace C library, currently packaged separately, that is
   optimized for correctness and small size.
  
-The cpio file format used by initramfs is the "newc" (aka "cpio -c")
+The cpio file format used by initramfs is the "newc" (aka "cpio -H newc")
 format, and is documented in the file "buffer-format.txt".  There are
 two ways to add an early userspace image: specify an existing cpio
 archive to be used as the image or have the kernel build process build
@@ -44,7 +44,7 @@
 CONFIG_INITRAMFS_SOURCE.  Sources can be either directories or files -
 cpio archives are *not* allowed when building from sources.
  
-A source directory will have it and all of it's contents packaged.  The
+A source directory will have it and all of its contents packaged.  The
 specified directory name will be mapped to '/'.  When packaging a
 directory, limited user and group ID translation can be performed.
 INITRAMFS_ROOT_UID can be set to a user ID that needs to be mapped to
@@ -144,7 +144,7 @@
    initrd format, an cpio archive.  It must be called "/init".  This binary
    is responsible to do all the things prepare_namespace() would do.
  
-   To remain backwards compatibility, the /init binary will only run if it
+   To maintain backwards compatibility, the /init binary will only run if it
    comes via an initramfs cpio archive.  If this is not the case,
    init/main.c:init() will run prepare_namespace() to mount the final root
    and exec one of the predefined init binaries.
@@ -8,7 +8,7 @@
  
 Ramfs is a very simple filesystem that exports Linux's disk caching
 mechanisms (the page cache and dentry cache) as a dynamically resizable
-ram-based filesystem.
+RAM-based filesystem.
  
 Normally all files are cached in memory by Linux.  Pages of data read from
 backing store (usually the block device the filesystem is mounted on) are kept
@@ -34,7 +34,7 @@
 ------------------
  
 The older "ram disk" mechanism created a synthetic block device out of
-an area of ram and used it as backing store for a filesystem.  This block
+an area of RAM and used it as backing store for a filesystem.  This block
 device was of fixed size, so the filesystem mounted on it was of fixed
 size.  Using a ram disk also required unnecessarily copying memory from the
 fake block device into the page cache (and copying changes back out), as well
@@ -46,8 +46,8 @@
 to avoid this copying by playing with the page tables, but they're unpleasantly
 complicated and turn out to be about as expensive as the copying anyway.)
 More to the point, all the work ramfs is doing has to happen _anyway_,
-since all file access goes through the page and dentry caches.  The ram
-disk is simply unnecessary, ramfs is internally much simpler.
+since all file access goes through the page and dentry caches.  The RAM
+disk is simply unnecessary; ramfs is internally much simpler.
  
 Another reason ramdisks are semi-obsolete is that the introduction of
 loopback devices offered a more flexible and convenient way to create
@@ -103,7 +103,7 @@
     initramfs archive is a gzipped cpio archive (like tar only simpler,
     see cpio(1) and Documentation/early-userspace/buffer-format.txt).  The
     kernel's cpio extraction code is not only extremely small, it's also
-    __init data that can be discarded during the boot process.
+    __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
     some setup and then returned to the kernel, while the init program from
@@ -220,7 +220,7 @@
 non-GPL code you'd like to run from initramfs, without conflating it with
 the GPL licensed Linux kernel binary).
  
-It can also be used to supplement the kernel's built-in initamfs image.  The
+It can also be used to supplement the kernel's built-in initramfs image.  The
 files in the external archive will overwrite any conflicting files in
 the built-in initramfs archive.  Some distributors also prefer to customize
 a single kernel image with task-specific initramfs images, without recompiling.
@@ -339,7 +339,7 @@
 The move to early userspace is necessary because finding and mounting the real
 root device is complex.  Root partitions can span multiple devices (raid or
 separate journal).  They can be out on the network (requiring dhcp, setting a
-specific mac address, logging into a server, etc).  They can live on removable
+specific MAC address, logging into a server, etc).  They can live on removable
 media, with dynamically allocated major/minor numbers and persistent naming
 issues requiring a full udev implementation to sort out.  They can be
 compressed, encrypted, copy-on-write, loopback mounted, strangely partitioned,
@@ -80,8 +80,8 @@
 ----------------------
  
 Recent kernels have support for populating a ramdisk from a compressed cpio
-archive, on such systems, the creation of a ramdisk image doesn't need to
-involve special block devices or loopbacks, you merely create a directory on
+archive. On such systems, the creation of a ramdisk image doesn't need to
+involve special block devices or loopbacks; you merely create a directory on
 disk with the desired initrd content, cd to that directory, and run (as an
 example):
  
@@ -293,7 +293,7 @@
 generated with all the necessary modules. Then, only /sbin/init or a file
 read by it would have to be different.
  
-A third scenario are more convenient recovery disks, because information
+A third scenario is more convenient recovery disks, because information
 like the location of the root FS partition doesn't have to be provided at
 boot time, but the system loaded from initrd can invoke a user-friendly
 dialog and it can also perform some sanity checks (or even some form of
@@ -339,8 +339,8 @@
 Mixed change_root and pivot_root mechanism
 ------------------------------------------
  
-In case you did not want to use root=/dev/ram0 to trig the pivot_root mechanism,
-you may create both /linuxrc and /sbin/init in your initrd image.
+In case you did not want to use root=/dev/ram0 to trigger the pivot_root
+mechanism, you may create both /linuxrc and /sbin/init in your initrd image.
  
 /linuxrc would contain only the following:
  
@@ -350,7 +350,7 @@
 umount -n /proc
  
 Once linuxrc exited, the kernel would mount again your initrd as root,
-this time executing /sbin/init. Again, it would be duty of this init
+this time executing /sbin/init. Again, it would be the duty of this init
 to build the right environment (maybe using the root= device passed on
 the cmdline) before the final execution of the real /sbin/init.
  
@@ -22,16 +22,21 @@
 RAM from the buffer cache. The driver marks the buffers it is using as dirty
 so that the VM subsystem does not try to reclaim them later.
  
-Also, the RAM disk supports up to 16 RAM disks out of the box, and can
-be reconfigured to support up to 255 RAM disks - change "#define NUM_RAMDISKS"
-in drivers/block/rd.c.  To use RAM disk support with your system, run
-'./MAKEDEV ram' from the /dev directory.  RAM disks are all major number 1, and
-start with minor number 0 for /dev/ram0, etc.  If used, modern kernels use
-/dev/ram0 for an initrd.
+The RAM disk supports up to 16 RAM disks by default, and can be reconfigured
+to support an unlimited number of RAM disks (at your own risk).  Just change
+the configuration symbol BLK_DEV_RAM_COUNT in the Block drivers config menu
+and (re)build the kernel.
  
+To use RAM disk support with your system, run './MAKEDEV ram' from the /dev
+directory.  RAM disks are all major number 1, and start with minor number 0
+for /dev/ram0, etc.  If used, modern kernels use /dev/ram0 for an initrd.
+
 The old "ramdisk=<ram_size>" has been changed to "ramdisk_size=<ram_size>" to
 make it clearer.  The original "ramdisk=<ram_size>" has been kept around for
 compatibility reasons, but it may be removed in the future.
+There are also config symbols (in the Block drivers config menu) for these
+variables:  BLK_DEV_RAM_SIZE defaults to 4096 and BLK_DEV_RAM_BLOCKSIZE
+defaults to 1024.
  
 The new RAM disk also has the ability to load compressed RAM disk images,
 allowing one to squeeze more programs onto an average installation or
...	...	@@ -19,7 +19,7 @@
19	19	- klibc, a userspace C library, currently packaged separately, that is
20	20	optimized for correctness and small size.
21	21
22		-The cpio file format used by initramfs is the "newc" (aka "cpio -c")
	22	+The cpio file format used by initramfs is the "newc" (aka "cpio -H newc")
23	23	format, and is documented in the file "buffer-format.txt". There are
24	24	two ways to add an early userspace image: specify an existing cpio
25	25	archive to be used as the image or have the kernel build process build
...	...	@@ -44,7 +44,7 @@
44	44	CONFIG_INITRAMFS_SOURCE. Sources can be either directories or files -
45	45	cpio archives are not allowed when building from sources.
46	46
47		-A source directory will have it and all of it's contents packaged. The
	47	+A source directory will have it and all of its contents packaged. The
48	48	specified directory name will be mapped to '/'. When packaging a
49	49	directory, limited user and group ID translation can be performed.
50	50	INITRAMFS_ROOT_UID can be set to a user ID that needs to be mapped to
...	...	@@ -144,7 +144,7 @@
144	144	initrd format, an cpio archive. It must be called "/init". This binary
145	145	is responsible to do all the things prepare_namespace() would do.
146	146
147		- To remain backwards compatibility, the /init binary will only run if it
	147	+ To maintain backwards compatibility, the /init binary will only run if it
148	148	comes via an initramfs cpio archive. If this is not the case,
149	149	init/main.c:init() will run prepare_namespace() to mount the final root
150	150	and exec one of the predefined init binaries.
...	...	@@ -8,7 +8,7 @@
8	8
9	9	Ramfs is a very simple filesystem that exports Linux's disk caching
10	10	mechanisms (the page cache and dentry cache) as a dynamically resizable
11		-ram-based filesystem.
	11	+RAM-based filesystem.
12	12
13	13	Normally all files are cached in memory by Linux. Pages of data read from
14	14	backing store (usually the block device the filesystem is mounted on) are kept
...	...	@@ -34,7 +34,7 @@
34	34	------------------
35	35
36	36	The older "ram disk" mechanism created a synthetic block device out of
37		-an area of ram and used it as backing store for a filesystem. This block
	37	+an area of RAM and used it as backing store for a filesystem. This block
38	38	device was of fixed size, so the filesystem mounted on it was of fixed
39	39	size. Using a ram disk also required unnecessarily copying memory from the
40	40	fake block device into the page cache (and copying changes back out), as well
...	...	@@ -46,8 +46,8 @@
46	46	to avoid this copying by playing with the page tables, but they're unpleasantly
47	47	complicated and turn out to be about as expensive as the copying anyway.)
48	48	More to the point, all the work ramfs is doing has to happen _anyway_,
49		-since all file access goes through the page and dentry caches. The ram
50		-disk is simply unnecessary, ramfs is internally much simpler.
	49	+since all file access goes through the page and dentry caches. The RAM
	50	+disk is simply unnecessary; ramfs is internally much simpler.
51	51
52	52	Another reason ramdisks are semi-obsolete is that the introduction of
53	53	loopback devices offered a more flexible and convenient way to create
...	...	@@ -103,7 +103,7 @@
103	103	initramfs archive is a gzipped cpio archive (like tar only simpler,
104	104	see cpio(1) and Documentation/early-userspace/buffer-format.txt). The
105	105	kernel's cpio extraction code is not only extremely small, it's also
106		- __init data that can be discarded during the boot process.
	106	+ __init text and data that can be discarded during the boot process.
107	107
108	108	- The program run by the old initrd (which was called /initrd, not /init) did
109	109	some setup and then returned to the kernel, while the init program from
...	...	@@ -220,7 +220,7 @@
220	220	non-GPL code you'd like to run from initramfs, without conflating it with
221	221	the GPL licensed Linux kernel binary).
222	222
223		-It can also be used to supplement the kernel's built-in initamfs image. The
	223	+It can also be used to supplement the kernel's built-in initramfs image. The
224	224	files in the external archive will overwrite any conflicting files in
225	225	the built-in initramfs archive. Some distributors also prefer to customize
226	226	a single kernel image with task-specific initramfs images, without recompiling.
...	...	@@ -339,7 +339,7 @@
339	339	The move to early userspace is necessary because finding and mounting the real
340	340	root device is complex. Root partitions can span multiple devices (raid or
341	341	separate journal). They can be out on the network (requiring dhcp, setting a
342		-specific mac address, logging into a server, etc). They can live on removable
	342	+specific MAC address, logging into a server, etc). They can live on removable
343	343	media, with dynamically allocated major/minor numbers and persistent naming
344	344	issues requiring a full udev implementation to sort out. They can be
345	345	compressed, encrypted, copy-on-write, loopback mounted, strangely partitioned,
...	...	@@ -80,8 +80,8 @@
80	80	----------------------
81	81
82	82	Recent kernels have support for populating a ramdisk from a compressed cpio
83		-archive, on such systems, the creation of a ramdisk image doesn't need to
84		-involve special block devices or loopbacks, you merely create a directory on
	83	+archive. On such systems, the creation of a ramdisk image doesn't need to
	84	+involve special block devices or loopbacks; you merely create a directory on
85	85	disk with the desired initrd content, cd to that directory, and run (as an
86	86	example):
87	87
...	...	@@ -293,7 +293,7 @@
293	293	generated with all the necessary modules. Then, only /sbin/init or a file
294	294	read by it would have to be different.
295	295
296		-A third scenario are more convenient recovery disks, because information
	296	+A third scenario is more convenient recovery disks, because information
297	297	like the location of the root FS partition doesn't have to be provided at
298	298	boot time, but the system loaded from initrd can invoke a user-friendly
299	299	dialog and it can also perform some sanity checks (or even some form of
...	...	@@ -339,8 +339,8 @@
339	339	Mixed change_root and pivot_root mechanism
340	340	------------------------------------------
341	341
342		-In case you did not want to use root=/dev/ram0 to trig the pivot_root mechanism,
343		-you may create both /linuxrc and /sbin/init in your initrd image.
	342	+In case you did not want to use root=/dev/ram0 to trigger the pivot_root
	343	+mechanism, you may create both /linuxrc and /sbin/init in your initrd image.
344	344
345	345	/linuxrc would contain only the following:
346	346
...	...	@@ -350,7 +350,7 @@
350	350	umount -n /proc
351	351
352	352	Once linuxrc exited, the kernel would mount again your initrd as root,
353		-this time executing /sbin/init. Again, it would be duty of this init
	353	+this time executing /sbin/init. Again, it would be the duty of this init
354	354	to build the right environment (maybe using the root= device passed on
355	355	the cmdline) before the final execution of the real /sbin/init.
356	356
...	...	@@ -22,16 +22,21 @@
22	22	RAM from the buffer cache. The driver marks the buffers it is using as dirty
23	23	so that the VM subsystem does not try to reclaim them later.
24	24
25		-Also, the RAM disk supports up to 16 RAM disks out of the box, and can
26		-be reconfigured to support up to 255 RAM disks - change "#define NUM_RAMDISKS"
27		-in drivers/block/rd.c. To use RAM disk support with your system, run
28		-'./MAKEDEV ram' from the /dev directory. RAM disks are all major number 1, and
29		-start with minor number 0 for /dev/ram0, etc. If used, modern kernels use
30		-/dev/ram0 for an initrd.
	25	+The RAM disk supports up to 16 RAM disks by default, and can be reconfigured
	26	+to support an unlimited number of RAM disks (at your own risk). Just change
	27	+the configuration symbol BLK_DEV_RAM_COUNT in the Block drivers config menu
	28	+and (re)build the kernel.
31	29
	30	+To use RAM disk support with your system, run './MAKEDEV ram' from the /dev
	31	+directory. RAM disks are all major number 1, and start with minor number 0
	32	+for /dev/ram0, etc. If used, modern kernels use /dev/ram0 for an initrd.
	33	+
32	34	The old "ramdisk=<ram_size>" has been changed to "ramdisk_size=<ram_size>" to
33	35	make it clearer. The original "ramdisk=<ram_size>" has been kept around for
34	36	compatibility reasons, but it may be removed in the future.
	37	+There are also config symbols (in the Block drivers config menu) for these
	38	+variables: BLK_DEV_RAM_SIZE defaults to 4096 and BLK_DEV_RAM_BLOCKSIZE
	39	+defaults to 1024.
35	40
36	41	The new RAM disk also has the ability to load compressed RAM disk images,
37	42	allowing one to squeeze more programs onto an average installation or