[Info-vax] Request description of UFS for VMS person

[AEF]

On Apr 30, 3:05 pm, "Bob Eager" <rd... at spamcop.net> wrote:
> On Thu, 30 Apr 2009 18:21:29 UTC, AEF <spamsink2... at yahoo.com> wrote:
> > The whole point of "everything in Unix is a file" to me means that you
> > can treat all these things as files the same way. In ODS-2 everything
> > is a file or is in a file. You can dump any file, even the pagefile! I
> > don't have to write no stinkin' utilities. I can use file commands on
> > VMS files. I can't use file commands on the super block or an inode.
> > So in my book they are not "files". If files are as you define them,
> > then the claim "everything in Unix is just a file" becomes
> > meaningless.
>
> You're getting hung up on this phrase, which was just a shorthand for
> "everything in UNIX can be accessed by file I/O operations".

I've never heard that. And if so, so what?

>
> So, to use 'od' on the superblock in my FreeBSD system:
>
> dd if=/dev/ad4s1a skip=65536 count=1

If it were a file, I wouldn't need to do this.

>
> and pipe it into 'od' (I didn't show that as this newsreader is refusing
> to do the pipe symbol)
>
> Of, course, that's just one superblock; there are usually many copies.
>
> > I just want to know in what sense super blocks and inodes are files.
>
> Not sure where you got the original quote from anyway. It's a loose way
> of saying that all I/O is via files. OK< you may think it's a
> shortcoming that bits of disk data structures aren't available directly
> as their own files (they are available as parts of files, though). But

Then they're not files. (What disk strucutres are available as "part
of files", and what's the point? Are super blocks and inodes parts of
files?) I can use file commands on files: cp, rm, mv, etc. I can't use
these on super blocks or inodes. Therefore, super blocks or inodes are
not files. I never heard "file I/O operations". I heard files.

> that's just VMS-centrism. One could equally well complain that you have
> to write special programs to change obscure modes on devices in VMS, but
> you don't on UNIX.

What obscure modes are you talking about?

> Different doesn't mean bad. Live with it.

I never said either OS was better or worse. I was just saying that not
everything is a file in Unix. On an ODS-2 disk, everything is a file
and all the file commands pretty much work the same way on all the
files. In particular, you can DUMP any file. I never have to invoke
strange dd commands or write utilities. Everything on the disk really
*is* a file. But this is clearly not true for inodes and super blocks,
which shows that "Everything in Unix is just a file" is a bogus
statement.

My original statement:

[beg quote]

> Nobody said VMS was broken! The VMS file system has many advantages. I
> merely pointed out that ffs, at any rate, didn't seem to need a way to
> recover from that situation.

The primary one I can think of is that everything on the volume really
*is* a file. Everything in the volume is "transparent". In Unix, at
least the ones I have access to I don't know how to dump the super
block or inodes. And on one of them I can't even dump a directory!

So can you or anyone else tell us more of the advantages? And on the
Unix side if there is a way to read the super block and inodes? So
much for "everything is a file in Unix".

[end quote]

Later I said:

[beg quote]

Whatever Unix people mean when they say "Everything is just a file" as
if that we're supposed to be some big advantage or make things easier.

If it has an inode, it's a file.

Or, on a different level, if you can write it as a path it's a file.

The superblock and inode seem to be neither. If I have to write
utilities and hunt down the blocks myself, it isn't a file in my book.
If I have to put the parts together to make a car, it's not a car;
it's a pile of parts.

[end quote]

I never said either OS (or file system, for that matter) was better or
worse. I'm just annoyed that after always hearing that "Everything in
Unix is just a file" and then finding out that it's clearly not the
case. Just like when Bill Gunshannon complains that people say "You
never have to reboot VMS" when clearly you do -- for example with
upgrades and AUTOGEN. He's right about having to reboot VMS sometimes
(but I don't recall anyone saying you NEVER have to reboot VMS). But I
have yet to see anything in this thread that shows that super blocks
and inodes are "files". If they were files I could use file commands
on them. Even /dev/null, which isn't a file in the traditional sense
as it has no associated inode, can be listed with 'ls -l' and cp'ed
to. You can't do either with super blocks or inodes. If they were
files, you could. Therefore, the statement "Everything in Unix is just
a file" is bogus. I suppose that "if you can't run 'ls -l' on it, it
isn't a file" would be a good criterion.

> Bob Eager

AEF