IBM AIX

[Jamie Watson]

In article <807 at riddle.UUCP> andrew at riddle.UUCP (Andrew Beattie) writes:
>>I was wondering if anyone out there has already seen or know something
>>worth knowing about IBM's new "UNIX" operating system AIX ???
>
>I have only used it for a few hours, but I hated it!

I have been working with it for almost a year now, and I disagree very
strongly with your conclusion - but not with your specific points, as
you will see below.

>My problem was that not all serial lines are the same, you have ttys for
>terminals and something else for serial printers.  You have stty for setting
>up one and something completely different (and menu driven - yeugh!) for
>the other.  This did an excelent job of breaking all my printer interfaces.

Absolutely right.  The trick here is that AIX on the RT is a "hosted"
operating system; the machine is actually running something called VRM,
the Virtual Resource Manager.  IBM has done some very tricky things with
the printer interface, and their spooling system bears no resembalance
at all to either the SysV "lp" or BSD "lpr" system.  However, what they
have gained is that *all* printer devices look the same from AIX, whether
they are connected via serial or parallel interfaces, and they all act
the same regardless of whether you send things through the spooler or
simply dump directly to the device.  This is a very mixed blessing; it
makes me crazy to have to learn yet another spooler, especially one as
complex as the AIX spooler.  But I sure do like defining the serial line
characteristics once, and only once, and having them work correctly all
the time - even if I say 'cat foo > /dev/lp0'.

A more interesting side issue here is the entire area of defining and
accessing devices to AIX.  Defining devices to AIX is done with a
utility program (called "devices", oddly enough).  As far as I can tell,
the major number for a given device is constant (ttys are 15, the tape
drive is 1, disks are 0 and so on) but the minor number is assigned on
a purely sequential basis.  Serial ports are a good example of how this
can drive someone with Unix experience crazy.  We all know that the name
of the entry in the /dev directory is basically meaningless, since I can
create names or links called whatever I like.  But on the RT there are
several different kinds of serial ports (built in, or serial/parallel
adapter, or 4-port serial card, or 8-port card, or ...).  I assumed
that there would be some fixed scheme to the major/minor numbers for
these various types of serial ports, so I could always tell what was
what; I was wrong.  The major number for *all* serial ports is 15, and
the minor numbers are assigned sequentially, so there is no way to
tell, by name or number what port a particular serial device will be
associated with.  It all depends on the order the system administrator
defines them in.  I am still very disturbed by this every time I think
about it, but I have to say that so far, in a year of working with a
number of different RTs, this has never caused be a problem (yet).

>The engineer at the site tells me that everything in /etc is organised
>differently.

Well, I disagree with the extent of this statement.  *Some* things in
/etc are different, most notably there is no inittab or ttys file; they
have their own way of doing this.  Again, there are advantages to it,
but significant problems as well.  Not the least of which is having to
learn another way of managing things.  They supply some pretty nice
utility programs for doing this, but in my experience these programs
don't quite address all the issues, and once I figured out where the
files are that hold all the information, I've had fairly often had to
go in and adjust things by hand.  The important point here is that the
files are in fact still plain ascii files, and can be edited if you want
or need to do that rather than using their utility programs.

>Disclaimer:  As I said, I only used it for a few hours - your mileage
>may vary.

It is interesting to note that a year ago I was as rabid anti-IBM as
anyone in the Unix world.  I'd been burned by various of their other
Unix offerings, which were consistently poor.  However, I really like
AIX a lot; I've previously worked extensively with Plexus and Sun
systems, and provided software support and system administration for
the Swiss distributor for both of these, and I can honestly say that
I like AIX at least as well, if not better than, the Unix ports on
either of them.

jw