Peter Allan petermallan at gmail.com
Fri Aug 20 15:25:43 CDT 2021

The idea of using an RA81 drive as it is bigger sounds like a simple
solution, but does it actually give a larger /usr partition? Even though an
RD54 drive is not huge, most of it is not taken up by the root partition
plus the /usr partition, but is available for use as (on the video at
least) /user1.

I will give it a try after the weekend and see what happens.


Peter Allan

On Fri, 20 Aug 2021 at 17:38, Ethan Dicks <ethan.dicks at gmail.com> wrote:

> On Fri, Aug 20, 2021 at 11:50 AM Peter Allan via cctalk
> <cctalk at classiccmp.org> wrote:
> > I just installed Ultrix-11 3.1 using the ultrix31.tap file from
> > https://pdp-11.org.ru/files.pl?lang=en
> > which is the location from the comments in Stephen's Machine Room video
> on
> > YouTube that I think started this thread.
> >
> > It installed just fine, but just like the video, I ran out of space on
> /usr.
> /usr was usually tight back in the day.
> > How can I make a larger /usr partition? Is it possible to do this at
> > installation time? There did not seem to be an option for this. Can it be
> > done by using an additional disk? That would seem likely, but not what a
> > system manager back in the 70's or 80's would expect to need to do,
> > especially as there is a relatively large amount of space left to create
> > /user1.
> In the 70s and early 80s, it was not at all uncommon to have multiple
> disk drives mounted to add up to enough space, especially to put user
> files on their own device to keep them from competing with free space
> in the system areas.  Also, older, smaller disks were often cheaper
> than the newest/largest disk drives, or systems would be put together
> from repurposed hardware rather than purchasing new.  For a single
> data point, my employer bought a new RA81 in 1984.  For 424MB it was
> $24,000.  Most machines had a _lot_ less disk in those days.  Our main
> UNIX machine was an old 11/750 (2MB RAM) with 2x RK07 (28MB each).  It
> was quite a jump when I put Ultrix 1.1 on an 11/730 w/RB80.  The CPU
> was 30% slower, but it had 5MB of RAM and a 121MB disk, so as a
> machine that spent most of its time with a single user (me), it was
> fine.
> When disks were routinely 1-30MB (RK05... RK07 or RP03), it was
> totally common to have 2-3 disks on a machine.
> All that said, I looked over this install write-up and it seems to
> assume you have one disk and it slices and dices with default sizes...
> http://ftp.fibranet.cat/UnixArchive/Distributions/DEC/Fred-Ultrix3/setup-3.1.txt
> I've installed older versions of UNIX where you had to explicitly set
> up disks and partitions (where you _could_ resize partitions).  Prior
> to restoring the contents from tape.  That didn't appear to be as easy
> with this installer script.
> > I noted the options for installing software using soft links to other
> > locations. Was that the preferred method when installing additional
> > software?
> That was done, as was mounting an entire second disk for /usr.  One of
> the challenges is making sure you have enough tools accessible on the
> boot device to bring the machine up far enough to mount the additional
> devices.  This is part of why there are system tools in /bin,
> /usr/bin, etc.  You could depend on the contents of /bin being there
> before /usr was mounted.  Also, traditionally, programs in /bin were
> statically linked so that you didn't have to have specific libraries
> available at the time.
> The simplest solution, of course, is just get a bigger disk, but where
> that wasn't possible (which was most of the time), people did use soft
> links or multiple spindles to aggregate enough space to get by.
> Back in the day, I struggled to get enough disk space to install
> 2.9BSD on an 11/24.  Two RK07s would have been a luxury.  I had an
> RL02 (10MB) and I think maybe an RL01.  I could get the initial
> restore to work but I didn't have enough space to rebuild my kernel.
> -ethan

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