Ethan Dicks ethan.dicks at gmail.com
Fri Aug 20 11:38:02 CDT 2021

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

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...


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.


More information about the cctalk mailing list