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

[Bill Gunshannon]

In article <33c33267-2172-433d-9a98-fdd1b9cbda3b at y7g2000yqa.googlegroups.com>,
	AEF <spamsink2001 at yahoo.com> writes:
> On Apr 20, 4:34 pm, "Richard B. Gilbert" <rgilber... at comcast.net>
> wrote:
>> AEF wrote:
>> >  Hi,
>>
>> > Can anyone here point me to a reference that describes the Unix file
>> > system (UFS) at a level and detail similar to the that found in the
>> > reference below? I've Googled for it and looked at a few books and had
>> > no luck. Thanks!
>>
>> > Guide to OpenVMS File Applications, Section 1.2.2:
>>
>> >http://h71000.www7.hp.com/doc/731final/4506/4506pro_001.html#apps_fil...
>>
>> Most Unix books at least touch on the subject.
> 
> That's the problem: that's ALL they do. I've checked Wikipedia.
> Superficial description. A while back I checked Wikipedia about
> several file systems and the only one described in reasonable detail
> was -- drum roll . . . . . . . . . -- VMS!
> 
> What is the structure of the "super block"? How are the group
> cylinders organized and/or determined and made? What is their
> structure? How are inodes found by the OS? Directories seem to be
> mostly the same as in VMS: a one-to-one mapping of filenames to inode
> numbers (FID's in VMSland). I did notice some strange extra bytes in
> the equivalent of DUMP blah.DIR;1 output. I wonder what they are. Once
> the inode number is found from the filename, how does Unix find the
> actual inode? One Web page I read says some confusing words about a
> single block in the super block listing a free block's address and a
> pointer other "data blocks" containing 10 of them and more pointers
> and I don't know -- it didn't make any sense to me.
> 
> (Speaking of DUMP <blah>.DIR;1: Why do only some versions of 'od' read
> directory files? The version I have on a Solaris 10.something box -- I
> think it's the gnu or gcc or Linux-like or whatever version --
> complains that "Its a directory"? Well, duh. Another machine with
> Solaris 8 could read it just fine. We're talking about dumping bytes
> in a file. Is there something hard about this in Unix?)
> 
> In VMS you have INDEXF.SYS. When RMS, XQP, or whatever it is, is asked
> to find the data in a file, it reads the directory, finds the
> requested filename, learns its FID, goes to INDEXF.SYS finds the VBN
> for the file-header offset by some formula I can't recall offhand, and
> finally reads the file header with that number. And that file header
> tells you all about the file and which blocks contain its data. There
> is the bitmap in the INDEXF.SYS file that keeps track of whether a
> file header is in use. There is the 3-number FID: number, sequence
> number, relative volume number. Unix appears to only have the first.
> There's the home block, the boot block, the backups thereof,
> BITMAP.SYS, and so on. Where is the reference that describes the Unix
> equivalents of these?
> 
> Then there's the mysterious VMS deletion process which I'd love to
> learn. I only know about it from the strange ANAL/DISK errors about
> file headers being busy, deleted, quasi-deleted, or whatever. I'd love
> to learn about that too. [Fuzzy-memory-of-a-long-ago-event alert!] I
> once learned a little about it and kept a sample lying around, but
> it's been so long I can't recall just what that was! Wait, I think it
> was a file header without a filename being entered in any directory.
> If I have time I'll try to resurrect this. [Another fuzzy-memory-of-a-
> long-ago-event alert!] I think I even asked this question (re the file-
> deletion process) here once many years ago and if I did I never got a
> good answer.
> 
>>
>> What problem are you trying to solve?
> 
> I want to learn how UFS works at the level mentioned above. I don't
> have any particular problem to solve. I just want to learn it out of
> curiosity and in case I need it later.
> 
> I do know more or less about how hard and soft links work.
> 
> Thanks.
> 

Did you try entering "Unix File System" into Wikipedia?  And if that
isn't detailed enough, try some of the references at the bottom of the
page.

bill

-- 
Bill Gunshannon          |  de-moc-ra-cy (di mok' ra see) n.  Three wolves
billg999 at cs.scranton.edu |  and a sheep voting on what's for dinner.
University of Scranton   |
Scranton, Pennsylvania   |         #include <std.disclaimer.h>