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docs: filesystems: convert cramfs.txt to ReST

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- Add a SPDX header;
- Adjust document title;
- Some whitespace fixes and new line breaks;
- Mark literal blocks as such;
- Add table markups;
- Add it to filesystems/index.rst.

Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Acked-by: Nicolas Pitre <nico@fluxnic.net>
Link: https://lore.kernel.org/r/e87b267e71f99974b7bb3fc0a4a08454ff58165e.1581955849.git.mchehab+huawei@kernel.org
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
This commit is contained in:
Mauro Carvalho Chehab 2020-02-17 17:11:56 +01:00 committed by Jonathan Corbet
parent 471379a174
commit f1fa0e6028
2 changed files with 13 additions and 7 deletions
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19
Documentation/filesystems/cramfs.txt → Documentation/filesystems/cramfs.rst
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@ -1,12 +1,15 @@
.. SPDX-License-Identifier: GPL-2.0
Cramfs - cram a filesystem onto a small ROM ===========================================
Cramfs - cram a filesystem onto a small ROM
===========================================
cramfs is designed to be simple and small, and to compress things well. cramfs is designed to be simple and small, and to compress things well.
It uses the zlib routines to compress a file one page at a time, and It uses the zlib routines to compress a file one page at a time, and
allows random page access. The meta-data is not compressed, but is allows random page access. The meta-data is not compressed, but is
expressed in a very terse representation to make it use much less expressed in a very terse representation to make it use much less
diskspace than traditional filesystems. diskspace than traditional filesystems.
You can't write to a cramfs filesystem (making it compressible and You can't write to a cramfs filesystem (making it compressible and
compact also makes it _very_ hard to update on-the-fly), so you have to compact also makes it _very_ hard to update on-the-fly), so you have to
@ -28,9 +31,9 @@ issue.
Hard links are supported, but hard linked files Hard links are supported, but hard linked files
will still have a link count of 1 in the cramfs image. will still have a link count of 1 in the cramfs image.
Cramfs directories have no `.' or `..' entries. Directories (like Cramfs directories have no ``.`` or ``..`` entries. Directories (like
every other file on cramfs) always have a link count of 1. (There's every other file on cramfs) always have a link count of 1. (There's
no need to use -noleaf in `find', btw.) no need to use -noleaf in ``find``, btw.)
No timestamps are stored in a cramfs, so these default to the epoch No timestamps are stored in a cramfs, so these default to the epoch
(1970 GMT). Recently-accessed files may have updated timestamps, but (1970 GMT). Recently-accessed files may have updated timestamps, but
@ -70,9 +73,9 @@ MTD drivers are cfi_cmdset_0001 (Intel/Sharp CFI flash) or physmap
(Flash device in physical memory map). MTD partitions based on such devices (Flash device in physical memory map). MTD partitions based on such devices
are fine too. Then that device should be specified with the "mtd:" prefix are fine too. Then that device should be specified with the "mtd:" prefix
as the mount device argument. For example, to mount the MTD device named as the mount device argument. For example, to mount the MTD device named
"fs_partition" on the /mnt directory: "fs_partition" on the /mnt directory::
$ mount -t cramfs mtd:fs_partition /mnt $ mount -t cramfs mtd:fs_partition /mnt
To boot a kernel with this as root filesystem, suffice to specify To boot a kernel with this as root filesystem, suffice to specify
something like "root=mtd:fs_partition" on the kernel command line. something like "root=mtd:fs_partition" on the kernel command line.
@ -90,6 +93,7 @@ https://github.com/npitre/cramfs-tools
For /usr/share/magic For /usr/share/magic
-------------------- --------------------
===== ======================= =======================
0 ulelong 0x28cd3d45 Linux cramfs offset 0 0 ulelong 0x28cd3d45 Linux cramfs offset 0
>4 ulelong x size %d >4 ulelong x size %d
>8 ulelong x flags 0x%x >8 ulelong x flags 0x%x
@ -110,6 +114,7 @@ For /usr/share/magic
>552 ulelong x fsid.blocks %d >552 ulelong x fsid.blocks %d
>556 ulelong x fsid.files %d >556 ulelong x fsid.files %d
>560 string >\0 name "%.16s" >560 string >\0 name "%.16s"
===== ======================= =======================
Hacker Notes Hacker Notes

1
Documentation/filesystems/index.rst
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@ -56,6 +56,7 @@ Documentation for filesystem implementations.
bfs bfs
btrfs btrfs
ceph ceph
cramfs
fuse fuse
overlayfs overlayfs
virtiofs virtiofs