More Summary: A Device Question

From: \ <thursday_at_allidaho.com>
Date: Wed, 13 Feb 2002 22:50:25 -0700

After the first summary I got these detailed response messages which
probably should be shared with the list. Tru64's whole system for
identifying filesystem devices appears to be a kind of hall of mirrors
....


This from Dr. Blinn:

Actually, it's messier than I stated.

Do an "ls -l /dev" and you'll see that in V5.x
/dev is a symlink that
leads to cluster/members/{memb}/dev, and that in
turn is a directory,
but in that directory is a mix of device special
files (for devices
that are NOT cluster shared, but are member
specific), and symlinks to
subdirectories under the /devices directory
(e.g., disk, rdisk, tape,
ntape):

sx164 (root) # ls -l /cluster/members/{memb}/dev
| grep devices
lrwxrwxrwx 1 root system 27 Oct
19 11:08 changer -> ../../../../devices/changer
lrwxrwxrwx 1 root system 25 Oct
19 11:08 cport -> ../../../../devices/cport
lrwxrwxrwx 1 root system 24 Oct
19 11:08 disk -> ../../../../devices/disk
lrwxrwxrwx 1 root system 25 Oct
19 11:08 dmapi -> ../../../../devices/dmapi
lrwxrwxrwx 1 root system 15 Oct
19 11:08 none -> ../devices/none
lrwxrwxrwx 1 root system 25 Oct
19 11:08 ntape -> ../../../../devices/ntape
lrwxrwxrwx 1 root system 25 Oct
19 11:08 rdisk -> ../../../../devices/rdisk
lrwxrwxrwx 1 root system 24 Oct
19 11:08 tape -> ../../../../devices/tape

It's remarkably complicated, and you don't want
to mess with it, but
the point is that the shortest path to the block
device name that you
want to mount in a V5.x system is something like
this:

        /devices/disk/dsk0a
rather than the equivalent (or should be
equivalent)
        /dev/disk/dsk0a

and in fact, if those are NOT the same device
special file, something
is messed up on your system.

Note that if you cd into /dev, you are off
somewhere under the cluster
hierarchy, in particular, in
/cluster/members/{memb}/dev and until you
do a pwd in there, you may not realize where you
are -- all part of the
magic of symbolic links and in particular CDSL
links (cluster member
dependent symbolic links). In a standalone
system, you're always in
"member0" but in a TruCluster you will be
somewhere else. Have fun
learning how all of this really works, it's not
well documented.

Tom


And this from William McGill, MIS guy from the University of
Pennsylvania ...



What you see depends upon how you got there.

As I remember, you will see a slightly different
structure in each version
if installed from scratch - 5.0 / 5.0A / 5.1 OR
if you upgrade.
...All part of the conversion into TruCluster
Support in 5.1.

For instance.... on a 5.1 installed system,
        /dev is a symlink to
/cluster/members/{memb}/dev/
not to /devices...

On a single system that will translate to:
        /cluster/members/member0/dev/

However, /cluster/members/member0/dev contains
links within it
to /devices:

        changer_at_ -> ../../../../devices/changer/
        cport_at_ -> ../../../../devices/cport/
        disk_at_ -> ../../../../devices/disk/
        ntape_at_ -> ../../../../devices/ntape/
        rdisk_at_ -> ../../../../devices/rdisk/
        rvol_at_ -> ../../../../devices/rvol/
        tape_at_ -> ../../../../devices/tape/
        vol_at_ -> ../../../../devices/vol/

In these cases, /dev really only contains the
pty and similar stuff.

I think that only a 5.1A INSTALLED system will
have /dev/as a link to
/devices. (I don't have a 5.1A system that was
installed handy, and I
don't remember if the upgrade actually changes
them or not, I would assume
that it does.)

-- 
                        www.tru64unix.compaq.com
                              www.tru64.org
This, with the previous summary, could almost make up a chapter in the
manual Compaq never wrote for Tru64.  Myself, i just hack away with a
copy of O'Reilly's Essentials of System Management open next to the
keyboard, with hope in my heart  ....  and of course the ability to send
in a question and get all these answers.
Give your valentine a kiss for me.
jn
PS is it still 1914?
Received on Thu Feb 14 2002 - 05:51:37 NZDT

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