[TUHS] observations on Unix v6's mount command

[TUHS] observations on Unix v6's mount command

[Mark Longridge]

I was trying to look at mini-unix so I mounted the disk image inside
unix v6 via:

/etc/mount /dev/rk4 /usr/mini-unix

and I noticed that if I ran the mount command as a user and not root
that /etc/mtab would not be updated (but it was updated as expected as
root). Of course /etc/mtab is owned by root :)

Then I noticed something else when I did an ls in the /usr directory:

drwxrwxrwx 20       31      368 Sep  3  1976 mini-unix

Normally I would see things like:

drwxrwxr-x  2 bin            48 May 13  1975 adm

What does the 31 mean?

Mark

[TUHS] observations on Unix v6's mount command

[Erik E. Fair]

The 31 is likely a UID number not found in /etc/passwd

Insofar as I know, you can set the ownership of a file to any arbitrary integer within the range of the uid_t (or whatever it was in ye olden days). See chown(8).

	Erik

[TUHS] observations on Unix v6's mount command

[Warren Toomey]

On Thu, Mar 09, 2017 at 01:25:32AM -0500, Mark Longridge wrote:
> Then I noticed something else when I did an ls in the /usr directory:
> 
> drwxrwxrwx 20       31      368 Sep  3  1976 mini-unix

Probably there is no username associated with uid 31 in the /etc/passwd file.

Cheers, Warren
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[TUHS] observations on Unix v6's mount command

[Ron Natalie]

When you mount the disk, the mount point displays the inode information of
the root directory of the mounted disk.
As Warren points out, that directory  is owned by user id 31, but your
machine has no passwd file entry for that uid.