News Group Posts

Mac OS X filesystems inodes

From: Tony Lawrence <tony@pcunix.com>
Subject: Re: Mac OSX Terminal dump/restore question
Date: Thu, 06 Feb 2003 10:31:39 GMT

Mark Conrad wrote:
> In article <eckleinspammenot-8E20C9.18064604022003@news.newsguy.com>,
> Ernie Klein <eckleinspammenot@pacbell.net> wrote:
> 
> 
>>I point this out because you seem to think that if you don't understand 
>>all of the options for a new command you are learning, then you are 
>>missing something and get frustrated. 
> 
> 
> Yep,it is my curious nature.  I figure it won't do much harm if I go
> over any options of interest, once lightly.  Might pay off big time in
> the future when I have a need for that option, assuming I can find my
> notes about it.
> 
> Is there an easy way to use the inode number to display all the inode
> data about a file?
> 
> I noted that the man page for "ls" describes the "i" option as listing
> the "file serial number".<g>

Any file system debugger can display a particular inode.  However, the 
only information there that is not readily available other ways (ls -l 
etc.) is the actual storage allocation, which is seldom of interest, 
although that info would give you knowledge of file fragmentation if you 
felt you needed to know that (and for a lot of reasons, you probably don't)

On a system that has the somewhat common "fsdb" (Mac OS X does not) you 
could dump out inode 54618 with

echo "54618i" | fsdb /dev/root

What is interesting is this comment from 
<http://www.usenix.org/publications/library/proceedings/usenix2000/invitedtalks/sanchez_html>


"It is worth noting that the difference is behavior is in part due to 
the implementation of the respective filesystems.  In UFS, meta-data is 
store with the file's inode, and inodes are stored separately from file 
data.  In HFS+, the file meta-data is stored with the file data; there 
is no inode. "

And yet, we can apparently ACT as though these did have inodes: hard 
links work, ls -li displays a number that is relevant, etc. 
<http://developer.apple.com/technotes/tn/tn1150.html> talks about how 
HFS+ is implemented, but doesn't explain how that part of the 
abstraction works.



-- 
Tony Lawrence
Free SCO, Mac OS X and  Linux Skills Tests: 
http://aplawrence.com/skillstest.html

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