[TUHS] inode - does it have a meaning?

[TUHS] inode - does it have a meaning?

[David Barto via TUHS]

In a blog post today I read:

	In most modern file systems, those data structures are
	known as inodes, and their numbers are inode numbers,
	sometimes shortened to inodes. The term is thought
	to be a contraction of index node, which certainly
	makes sense, but is lost in the mists of time.

This was written by a fellow who is reasonably smart and knows
his way around things MacOS, though not things UNIX. So before
I go and tell him that inode really does mean ‘index node’, I’m
checking here to clear the “mists of time.”

I’ve always understood it to be a shortening of ‘index node’.

Wikipedia (https://en.wikipedia.org/wiki/Inode) says

	There has been uncertainty on the Linux kernel mailing list
	about the reason for the "i" in "inode". In 2002, the question
	was brought to Unix pioneer Dennis Ritchie, who replied:[4]
	
	In truth, I don't know either. It was just a term that we
	started to use. "Index" is my best guess, because of the
	slightly unusual file system structure that stored the
	access information of files as a flat array on the disk,
	with all the hierarchical directory information living
	aside from this. Thus the i-number is an index in this array,
	the i-node is the selected element of the array.
	(The "i-" notation was used in the 1st edition manual;
	its hyphen was gradually dropped.)

Further the Wikipedia article states that Bach says that the word ‘inode’
is a contraction of the term index node.

So is there a ‘definitive’ answer for this, or is it really lost in
the mists of time?

	David

Men always learn from their mistakes how to make new ones.
A.J.P. Taylor

David Barto
barto@kdbarto.org

[TUHS] Re: inode - does it have a meaning?

[steve jenkin via TUHS]

In 1989, Ken was interviewed by Mike Mahoney of Princeton, as part of the “Unix Oral History Project”.

It seems ‘inode’ was being used from 1969 when Ken & Dennis were doing design, with Rudd Canaday in his office.

======================

Princeton have removed the original site.

Copes can be found at:
	<https://dspinellis.github.io/oral-history-of-unix/Mahoney/unixhistory.htm>
	<https://mirror.math.princeton.edu/pub/unixarchive/Documentation/OralHistory/>

An edited summary by Mahoney:
	<https://mirror.math.princeton.edu/pub/unixarchive/Documentation/OralHistory/expotape.htm>

======================

Ken’s Interview of "9-6-89"
	<https://dspinellis.github.io/oral-history-of-unix/mike/transcripts/thompson.htm>

Thompson: Yeah. I was doing it on the 635 at the time. Yeah . 
I got these exponential curves where before it would get into trouble it would go way out and get lots and lots of simultaneous accesses going… 
I was playing with a disk sorting algorithms and caching algorithms at the time. 
All of those actually went into UNIX. Um.

MSM: This would be the research aspect of the work?

Thompson: Yeah. Then in the actual design. 
At that point, it just went to… 
There was a model of a user and a model of this, and they generated activities, 
and the activity went into the disks that were sorted and things like that. Um, um. 
It was never down to a design to the point of where you put the addresses, how you expand files and things like that. 
It was never down to that level. 
It was always at some higher level. 

I think it was just like one or two meetings, Dennis and Canaday and myself. 

Was just discussing these ideas of the general nature of keeping the files out of each other's hair and the nitty-gritty of expanding. 

Of the real implementation, where you put the block addresses, where you put this and this. 
I remember, um, we did it in Canaday's office. 
At the end of this discussion Canaday picked up the phone, 
	and there was a new service in Bell Laboratories, dictation, 
	where you call up essentially a tape recorder and you give notes,
	and then the next morning notes are typed and sent to you. 

The next day, these notes came back and the acronyms were butchered, like "inode" was "eyen" (Laughing).

======================

> On 5 Oct 2025, at 07:38, David Barto via TUHS <tuhs@tuhs.org> wrote:
> 
> In a blog post today I read:
> 
> 	In most modern file systems, those data structures are
> 	known as inodes, and their numbers are inode numbers,
> 	sometimes shortened to inodes. The term is thought
> 	to be a contraction of index node, which certainly
> 	makes sense, but is lost in the mists of time.
> 
> This was written by a fellow who is reasonably smart and knows
> his way around things MacOS, though not things UNIX. So before
> I go and tell him that inode really does mean ‘index node’, I’m
> checking here to clear the “mists of time.”
> 
> I’ve always understood it to be a shortening of ‘index node’.
> 
> Wikipedia (https://en.wikipedia.org/wiki/Inode) says
> 
> 	There has been uncertainty on the Linux kernel mailing list
> 	about the reason for the "i" in "inode". In 2002, the question
> 	was brought to Unix pioneer Dennis Ritchie, who replied:[4]
> 	
> 	In truth, I don't know either. It was just a term that we
> 	started to use. "Index" is my best guess, because of the
> 	slightly unusual file system structure that stored the
> 	access information of files as a flat array on the disk,
> 	with all the hierarchical directory information living
> 	aside from this. Thus the i-number is an index in this array,
> 	the i-node is the selected element of the array.
> 	(The "i-" notation was used in the 1st edition manual;
> 	its hyphen was gradually dropped.)
> 
> Further the Wikipedia article states that Bach says that the word ‘inode’
> is a contraction of the term index node.
> 
> So is there a ‘definitive’ answer for this, or is it really lost in
> the mists of time?
> 
> 	David
> 
> Men always learn from their mistakes how to make new ones.
> A.J.P. Taylor
> 
> David Barto
> barto@kdbarto.org
> 
> 
> 

--
Steve Jenkin, IT Systems and Design 
0412 786 915 (+61 412 786 915)
PO Box 38, Kippax ACT 2615, AUSTRALIA

mailto:sjenkin@canb.auug.org.au http://members.tip.net.au/~sjenkin

[TUHS] Re: inode - does it have a meaning?

[Steffen Nurpmeso via TUHS]

David Barto via TUHS wrote in
 <143E170E-F64F-4AEE-83B1-BAB134267099@kdbarto.org>:
 |In a blog post today I read:
 |
 | In most modern file systems, those data structures are
 | known as inodes, and their numbers are inode numbers,
 | sometimes shortened to inodes. The term is thought
 | to be a contraction of index node, which certainly
 | makes sense, but is lost in the mists of time.
 |
 |This was written by a fellow who is reasonably smart and knows
 |his way around things MacOS, though not things UNIX. So before
 |I go and tell him that inode really does mean ‘index node’, I’m
 |checking here to clear the “mists of time.”
 |
 |I’ve always understood it to be a shortening of ‘index node’.
 |
 |Wikipedia (https://en.wikipedia.org/wiki/Inode) says
 |
 | There has been uncertainty on the Linux kernel mailing list
 | about the reason for the "i" in "inode". In 2002, the question
 | was brought to Unix pioneer Dennis Ritchie, who replied:[4]
 | 
 | In truth, I don't know either. It was just a term that we
 | started to use. "Index" is my best guess, because of the
 | slightly unusual file system structure that stored the
 | access information of files as a flat array on the disk,
 | with all the hierarchical directory information living
 | aside from this. Thus the i-number is an index in this array,
 | the i-node is the selected element of the array.
 | (The "i-" notation was used in the 1st edition manual;
 | its hyphen was gradually dropped.)
 |
 |Further the Wikipedia article states that Bach says that the word ‘inode’
 |is a contraction of the term index node.
 |
 |So is there a ‘definitive’ answer for this, or is it really lost in
 |the mists of time?

Sure is to me only that in 4.2BSD the "A Fast File System for
UNIX" paper (share/doc/smm/05.fastfs/) talks

  +Every file has a descriptor associated with it called an
  +.I "inode".
  +The inode contains information describing ownership of the file,
  +time stamps marking last modification and access times for the file,
  +and an array of indices that point to the data blocks for the file.
  +For the purposes of this section, we assume that the first 8 blocks
  +of the file are directly referenced by values stored
  +in the inode structure itself*.

Node with array of indices.
Isn't this an influential paper?  Not mentioned in Wikipedia.

--steffen
|
|Der Kragenbaer,                The moon bear,
|der holt sich munter           he cheerfully and one by one
|einen nach dem anderen runter  wa.ks himself off
|(By Robert Gernhardt)

[TUHS] Re: inode - does it have a meaning?

[Jon Forrest via TUHS]

On 10/4/25 1:38 PM, David Barto via TUHS wrote:
> In a blog post today I read:
> 
> 	In most modern file systems, those data structures are
> 	known as inodes, and their numbers are inode numbers,
> 	sometimes shortened to inodes. The term is thought
> 	to be a contraction of index node, which certainly
> 	makes sense, but is lost in the mists of time.

The "provably secure" version of Unix, called KSOS, used
"jnodes" instead of "inodes". I think this was because the
main architect of KSOS was Jay McCauley, and he named them
after himself.

Jon

[TUHS] Re: inode - does it have a meaning?

[Noel Chiappa via TUHS]

    > From: Steffen Nurpmeso

    > Isn't this an influential paper.

Written well over a decade after initial UNIX. The chances that anyone there
knew anything about very early UNIX (especially as old documents had not yet
started to show up on the early Internet, back then) are zero.

	Noel

[TUHS] Re: inode - does it have a meaning?

[Warner Losh via TUHS]

On Sat, Oct 4, 2025 at 5:16 PM Noel Chiappa via TUHS <tuhs@tuhs.org> wrote:

>     > From: Steffen Nurpmeso
>
>     > Isn't this an influential paper.
>
> Written well over a decade after initial UNIX. The chances that anyone
> there
> knew anything about very early UNIX (especially as old documents had not
> yet
> started to show up on the early Internet, back then) are zero.
>

 Yet they could have had it from oral history, given Ken's 1975
sabbatical to Berkeley, no? And the paper pre-dates his later
recollections, and surely he reviewed it and would have raised an objection
if he knew it was wrong. Kirk McKusick, the author, is on this list, I
think. Though, I will grant it's not primary evidence.

Warner

[TUHS] Re: inode - does it have a meaning?

[Warren Toomey via TUHS]

On Sat, Oct 04, 2025 at 01:38:00PM -0700, David Barto via TUHS wrote:
> In a blog post today I read:
> 
> 	In most modern file systems, those data structures are
> 	known as inodes, and their numbers are inode numbers,
> 	sometimes shortened to inodes. The term is thought
> 	to be a contraction of index node, which certainly
> 	makes sense, but is lost in the mists of time.

This is in the 197 CACM paper:

  A directory entry contains only a name for the associated file and
  a pointer to the file itself. This pointer is an integer called the
  i-number (for index number) of the file. When the file is accessed, its
  i-number is used as an index into a system table (the i-list) stored in
  a known part of the device on which the directory resides. The entry
  thereby found (the file’s i-node) contains the description of the file ...

But an earlier version of the paper has this:

  A directory entry contains only a name for the associated file and
  a pointer to the file itself. This pointer is an integer called the
  i-number (for identification number) of the file.

See https://github.com/DoctorWkt/unix_timesharing_paper/blob/master/filesystem.md

So you could argue that, at the time of this draft, the wording implies
"identification node" for i-node.

Cheers, Warren

[TUHS] Re: inode - does it have a meaning?

[Marc Donner via TUHS]

Pedant alert: inode - does it have an etymology.  We know what it *MEANS*
... that's in some man page.\
=====
mindthegapdialogs.com <https://www.mindthegapdialogs.com>
north-fork.info <https://www.north-fork.info>


On Sun, Oct 5, 2025 at 1:04 AM Warren Toomey via TUHS <tuhs@tuhs.org> wrote:

> On Sat, Oct 04, 2025 at 01:38:00PM -0700, David Barto via TUHS wrote:
> > In a blog post today I read:
> >
> >       In most modern file systems, those data structures are
> >       known as inodes, and their numbers are inode numbers,
> >       sometimes shortened to inodes. The term is thought
> >       to be a contraction of index node, which certainly
> >       makes sense, but is lost in the mists of time.
>
> This is in the 197 CACM paper:
>
>   A directory entry contains only a name for the associated file and
>   a pointer to the file itself. This pointer is an integer called the
>   i-number (for index number) of the file. When the file is accessed, its
>   i-number is used as an index into a system table (the i-list) stored in
>   a known part of the device on which the directory resides. The entry
>   thereby found (the file’s i-node) contains the description of the file
> ...
>
> But an earlier version of the paper has this:
>
>   A directory entry contains only a name for the associated file and
>   a pointer to the file itself. This pointer is an integer called the
>   i-number (for identification number) of the file.
>
> See
> https://github.com/DoctorWkt/unix_timesharing_paper/blob/master/filesystem.md
>
> So you could argue that, at the time of this draft, the wording implies
> "identification node" for i-node.
>
> Cheers, Warren
>