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The Filesystems HOWTO is about filesystems and accessing filesystems from
various OS. Although this document has been put together to the best of my
knowledge, it may and probably does contain mistakes. Please if you find some
mistake or outdated information, let me know. I will try to keep this document
up to date and as error free as possible. Any contributions are also welcome, so
if you want to write anything about filesystems, please contact me via e-mail.
Before you read this HOWTO it's recommended to read
Stein Gjoen's
Disk-HOWTO (you can obtain it from
http://sunsite.unc.edu/LDP/HOWTO/
).
This HOWTO can be obtained from
http://penguin.cz/~mhi/fs/ or
http://metalab.unc.edu/filesystems/howto/.
If you are Japanese user, you might be interested that
FUJIWARA Teruyoshi
translated this HOWTO to Japanese.
It is available at
http://www.linux.or.jp/JF/JFdocs/Filesystems-HOWTO.html.
SGML source file can be downloaded from
ftp://ftp.linet.gr.jp/pub/JF/sgml/Filesystems-HOWTO.sgml.gz.
The Filesystems HOWTO, Copyright (c) 1999 Martin Hinner
<
mhi@penguin.cz>.
This HOWTO is free document; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or (at
your option) any later version.
This HOWTO is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
General Public License for more details.
You should have received a copy of the GNU General Public License
along with this document or GNU CC; if not, write to the:
Free Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139,
USA.
You may want to join Filesystems mailing list. It's intended to be a good
source of information for both end-users and developers. So if you have
anything to do with filesystems, join ;-) To subscribe send email to
<
majordomo@penguin.cz>
and in the BODY (not the subject) of the email message put (without quotes):
"subscribe fs-l".
Linux kernel filesystems mailing-list
To join Linux kernel filesystems mailing list
linux-fsdev@vger.rutgers.edu,
send e-mail to
listserv@vger.rutgers.edu. Put "subscribe linux-fsdev"
in message body.
FreeBSD filesystems mailing-list
To join techical FreeBSD filesystems mailing list
freebsd-fs@FreeBSD.org,
send e-mail to
majordomo@FreeBSD.org. Put
"subscribe freebsd-fs" in message body.
Filesystems collection is FTP/WWW site providing useful information about
filesystems and filesystem-related programs and drivers. It lives at
http://metalab.unc.edu/filesystems/, or FTP-only at
ftp://metalab.unc.edu/pub/docs/filesystems/.
The original "Filesystems access HOWTO" was written by Georgatos Photis
(see his homepage at
http://students.ceid.upatras.gr/~gef/).
This HOWTO contains a lot of information from his webpage. Thanks, Gef.
FUJIWARA Teruyoshi <fujiwara@linux.or.jp> translated this HOWTO
to Japanese.
Other people who have contributed or helped me (directly or indirectly)
with this HOWTO are, in alphabetical order:
- Mariusz Borkowski <borkowsm@ii.pw.edu.pl> - ISO9660/RR info
- Remy Card <card@masi.ibp.fr> - Ext2 filesystem introduction
- Peter A. Dinda <pdinda@cs.cmu.edu> - HFS filesystem description
- Alfonso De Gregorio <adg@speedcom.it> - TCFS filesystem info
- Radek Machacka <radekm@sco.com> - Thanks for SCO UnixWare
and SCO OpenServer
- Andrey Shedel <andreys@cr.cyco.com> - Misc. updates
- Peter Todd <retep2@home.com> - SFS filesystem info
- Theodore Ts'o <tytso@mit.edu> - Ext2 filesystem introduction
- Stephen Tweedie <sct@dcs.ed.ac.uk> - Ext2 filesystem introduction
Many thanks to the above people. If I have forgotten anyone, please let me know.
This is filesystem accessibility "map", alphabetically ordered by operating
system. You may find this list a little bit chaotic. It's because Linux
sgmltools don't know tables.
YOU SEE THAT THIS `MAP' IS NOT STILL COMPLETE.
I WILL TRY TO FINISH IT IN THE NEAR FUTURE.
FreeBSD:
BSD FFS |
Ext2 |
HPFS |
NTFS
Linux:
AFFS|
BeFS|
BFS|
Ext2 FS|
BSD FFS|
HPFS|
Qnx4 FS|
Xia
NetBSD:
BSD FFS |
FAT12/16 |
ISO9660
NetWare 2.x:
NWFS-286
NetWare 3.x, 4.x:
NWFS-386 |
ISO9660
NetWare 5.x:
NWFS-386 |
NSS |
ISO9660
OpenBSD:
BSD FFS |
FAT12/16
OS/2:
Ext2 FS |
FAT12/16/32 |
HPFS |
HPFS |
ISO 9660 |
JFS |
VFAT
QNX 4:
FAT12/16 |
ISO 9660 |
Qnx4 FS
SCO OpenServer:
AFS|
DTFS|
EAFS|
HTFS|
ISO 9660 |
S51K
SCO UnixWare:
BFS|
DTFS|
ISO 9660 |
System V|
VxFS
Some contiguous filesystems:
BFS,
ISO9660 and extensions.
(todo)
Some FAT filesystems:
FAT12/16/32, VFAT and
NetWare filestem.
(todo)
(todo)
Some 'extent' filesystems:
EFS and
VxFS.
(todo)
Some filesystems which use B+ trees:
HFS,
NSS,
Reiser FS and
Spiralog filesystem.
File systems update their structural information (called
metadata) by synchronous writes. Each metadata update may require many
separate writes, and if the system crashes during the write sequence, metadata
may be in inconsistent state.
At the next boot the filesystem check utility (called fsck) must walk
through the metadata structures, examining and repairing them.
This operation takes a very very long time on large filesystems.
And the disk may not contain sufficient information
to correct the structure. This results in misplaced or removed files.
A journaling file system uses a separate area called a log or journal.
Before metadata changes are actually performed, they are logged to this separate
area. The operation is then performed. If the system crashes during
the operation, there is enough information in the log to "replay" the log
record and complete the operation.
This approach does not require a full
scan of the file system, yielding very quick filesystem check time on
large file systems,
generally a few seconds for a multiple-gigabyte file system. In addition,
because all information for the pending operation is saved, no removals
or lost-and-found moves are required. Disadvantage of journaling filesystems
is that they are slower than other filesystems.
Some journaling filesystems:
BeFS,
HTFS,
JFS,
NSS,
Spiralog filesystem,
VxFS and
XFS.
Quota
Snapshot
ACLs
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