[TUHS] UINX Program Description: For V6 Unix.

[Rik Farrow via TUHS]

Thanks, that's actually very interesting. One the second page, update() is
described as including a lock to prevent it being called a second time
before the first call is completed. That explained to me the lore I picked
up at UC Berkeley about typing "sync;sync". I wondered why it was necessary
to use sync twice, and the answer is that it's not: the first invocation
appears to return immediately but invoked sync the second time waits until
the first finishes--so you can tell updating of inodes and superblocks has
completed.

I'd heard that VAX systems running Unix were slow enough that experienced
users could tell the system was becoming unstable and type sync. There was
also a 'sync' user account, so typing 'sync' as a username would fire off
update().

Rik


On Fri, Jan 2, 2026 at 11:40 AM David Barto via TUHS <tuhs at tuhs.org> wrote:

> May I suggest that the following is a good read for V6 internals. Without
> source, and a well written description of functions.
>
>         David
>
>
> https://archive.org/details/unix_program_description_jan_1976/page/n5/mode/2up
> 
> UNIX Program Description : Bell Telephone Laboratiories, Incorporated :
> Free Download, Borrow, and Streaming : Internet Archive
> archive.org
>
>
> > On Jan 2, 2026, at 1:14 AM, Jonathan Gray via TUHS <tuhs at tuhs.org>
> wrote:
> >
> > On Sun, Dec 28, 2025 at 10:38:37PM +0000, Thalia Archibald via TUHS
> wrote:
> >> On Dec 28, 2025, at 14:12, segaloco via TUHS <tuhs at tuhs.org> wrote:
> >>> First image is V6 (+BTL Lions Commentary)
> >>
> >> I thought that Lions’ Commentary wasn’t distributed after BTL took over
> distribution?
> >> Do you know whether there’s a scan of that version anywhere?
> >>
> >> The BTL takeover was announced in the March 1978 issue of ;login:.
> >>    https://archive.org/details/login_march-1978/page/n1/mode/1up
> >>
> >> Thalia
> >
> > Licensees were allowed to have one copy from BTL.
> >
> > https://archive.org/details/login_nov84_issue/page/n25/mode/1up
> > https://www.tuhs.org/Usenet/comp.unix.wizards/1981-June/000459.html
> > https://www.tuhs.org/Usenet/comp.unix.wizards/1986-January/015591.html
>
>