[TUHS] Unix v6 File System information

Clem Cole clemc at ccc.com
Mon Feb 22 04:59:38 AEST 2016

​Will Senn asked

> Supposing I created a byte faithful representation of a V6 filesystem

 > on my mac, would I then be able to load the file in simh as an RK05 and
>  > mount and access its files and directories from a V6 instance?

​Not 100% sure how to parse this... but that is exactly how simh (and

​ work.
You have a UNIX file on your mac and at the simh interactive command
system, you "attach" it as the data for the simulated RK05.
​But it's a manual process to do the attachment AND more importantly,
since Mac OSx just sees it as bits, as a minimum you need to write tools to
push/pull V6 "files" from the image.  This is the same as the "DOS Tools"
trick you see in a lot of UNIX systems that know how to "grok" DOS/FAT file
system images.   You would need to do the same thing.  If you poke around
the Warren's TUHS archives, you might find some of this already there.

​What many of us do it attach a file as a virtual disk but instead of using
a UNIX file system format, use it is a tape image.   Then use tar/cpio or
whatever if you already a tool on both sides that can interpret the bits.
Hence, the v6tar discussion of a few weeks ago.   The UNIX ar(1) format is
sometimes used also, since it was common.   cpio -c also works, but that
was not on the research systems.​   My old room mate, Tom Quarles, wrote a
really good ANSI tape reader/writer for BSD UNIX.  That should back port to
v6 with a little work, particularly if you the "typesetter C" compiler for
V6 which supported enough of the V7 C.   The advantage of the ANSI tape
format is that its common with the DEC systems as well as UNIX.

That said, you can be smarter and more automatic.   As Noel says Ersatz11
supports a virtual shared disk (the same way VMware and Parallels) do.
Writing such a device for simh would be cool and in fact useful for many
different emulators.  Warning there are a lot of dragons hidden with such a
shared FS.   At is definitely doable, but is going to take some work.

The other thing you could do that might be a little less work, but would be
Mac specific, is Mac OSX has the FUSE file system emulation that stuff that
Google released.  If hacked up support for the old Unix FS, you could mount
the V6 "disk" image as Mac OSx disk and see the bits with normal tools.
I've thought about doing this but I have never had the time.  If I ever
became a serious user of the simh, I would probably want something more
like this.

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