Old UNIX file system formats

Old UNIX file system formats

[Ken Wellsch]

I didn't see mention of the flag "HUGE" WRT the V6 file format.
Now I may be being mislead from my memory of Venix 1.x which is
a derivative of V6 (while Venix 2.x is SysIII I think).  If the
HUGE bit is set in the i-node, then and only then is the 8th
index pointer treated as the indirection variety.  Thus 8 block
or less files I think are directly indexed.  -- Ken

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On Sun, 31 Jan 1999, Ken Wellsch wrote:

> I didn't see mention of the flag "HUGE" WRT the V6 file format.
> Now I may be being mislead from my memory of Venix 1.x which is
> a derivative of V6 (while Venix 2.x is SysIII I think).  If the
> HUGE bit is set in the i-node, then and only then is the 8th
> index pointer treated as the indirection variety.  Thus 8 block
> or less files I think are directly indexed.  -- Ken

I think you're confusing LARGE with HUGE.  I don't have my Edition 5
manual handy, but in my Edition 6 manual if the LARGE bit is set then
the first seven inode pointers are indirect blocks (otherwise all
eight blocks are direct), and the eighth block is a double-indirect block.

-- 
Dave Horsfall VK2KFU  dave at geac.com.au  Ph: +61 2 9978-7493 Fx: +61 2 9978-7422
Geac Computers P/L (FGH Division) 2/57 Christie St, St Leonards 2065, Australia


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Subject: Re: Old UNIX file system formats
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> I didn't see mention of the flag "HUGE" WRT the V6 file format.
> Now I may be being mislead from my memory of Venix 1.x which is
> a derivative of V6 (while Venix 2.x is SysIII I think).  If the
> HUGE bit is set in the i-node, then and only then is the 8th
> index pointer treated as the indirection variety.  Thus 8 block
> or less files I think are directly indexed.  -- Ken

Hmm...  I wrote a disk image editor in Visual Basic without knowing the
specs for the filesystem -- I set it up so that if the 9th pointer is zero
and the filesize is greater than one block, then it assumed the block
pointed to by the 8th pointer was a list of blocks in the file.