* [TUHS] Re: ancient unix filesystems
[not found] <200205060206.g4626vm71633@minnie.tuhs.org>
@ 2002-05-06 3:59 ` Stuart Norris
2002-05-07 17:15 ` Sven Dehmlow
0 siblings, 1 reply; 2+ messages in thread
From: Stuart Norris @ 2002-05-06 3:59 UTC (permalink / raw)
On Mon, 6 May 2002 tuhs-request at minnie.tuhs.org wrote:
> From: Warren Toomey <wkt at minnie.tuhs.org>
>
> Sven, you might want to look at this:
> http://minnie.tuhs.org/cgi-bin/pups.cgi?article=2170
>
> From: Stuart Norris <norris at euler.mech.eng.usyd.edu.au>
>
> I have hacked together a version of a Unix 5th (and 6th)
> Edition filesystem for Linux. It is read only, and was written for
> Linux 2.0 on an x86 and so will require a little work to install on
> other systems and newer kernels, but it is fun to be able to mount
> old disk images.
The source code is sitting on
http://www.esc.auckland.ac.nz/People/Staff/Norris/src/u5e-0.2.tar.gz
and the INTRO file contains a description of the filesystem. I don't think
it works with current Linux kernels (I havn't touched it for a long while),
so it might be easiest to start afresh using the minix filesystem module
as a start.
Briefly, the filesystem is like
--
* Block size: 512
* General layout:
Block 0 boot block
Block 1 super block
Blocks 2 -> isize-1 inodes
Blocks isize -> fsize-1 data blocks
* Byte ordering of "short" (16 bit entities) is little endian 0 1
* Byte ordering of "long" (32 bit entities) is PDP-11 2 3 0 1
* Inode on disk: "short"
0 means non-existent
1 root dir
* Maximum number of hard links to a file: 256
* Super-block location: bytes 512-1023
* Super-block layout:
unsigned short s_isize; /* size in blocks of I list */
unsigned short s_fsize; /* size in blocks of entire volume */
unsigned short s_nfree; /* number of in core free blocks (0-100) */
unsigned short s_free[100]; /* in core free blocks */
unsigned short s_ninode; /* number of in core I nodes (0-100) */
unsigned short s_inode[100];/* in core free I nodes */
char s_flock; /* lock during free list manipulation */
char s_ilock; /* lock during I list manipulation */
char s_fmod; /* super block modified flag */
char s_ronly; /* mounted read-only flag */
unsigned long s_time; /* current date of last update */
* Inode layout:
unsigned short i_mode; /* access permissions */
unsigned char i_nlink; /* number of links to file */
unsigned char i_uid; /* owner */
unsigned char i_gid; /* group */
unsigned char i_size0; /* size of file */
unsigned short i_size1;
unsigned short i_addr[8];/* address of blocks */
unsigned long i_atime; /* time of last access */
unsigned long i_mtime; /* time of last modification */
* Regular file data blocks are organized as
if (010000 bit set)
the file is large:
i_addr[] contains indirect blocks
else
the file is small:
* Inode size 32, 16 inodes per block
* Directory entry on disk
unsigned short inode;
char name[14];
* Dir entry size 16, 32 dir entries per block
* There are no symbolic links
--
Stuart Norris s.norris at auckland.ac.nz
Bioengineering Institute, University of Auckland hm: +(64 9) 307 0006
http://www.esc.auckland.ac.nz/People/Staff/Norris wk: +(64 9) 373 7599 x3055
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