Symbolic user names and RFS

[Lindsay F. Marshall]

In article <674 at oliveb.UUCP> jerry at oliveb.UUCP (Jerry Aguirre) writes:
>I installed the remote file system (RFS) distributed over the net and
>found a big gotcha that other users should be aware of.
>
	..........
>
>Anybody know how this is handled on other networked file systems?
>

One point you have forgotten here is that at the level of the file
system you are working with numeric uids NOT names - this is an
unfortunate fact of life. Thus, having access to both password files
doesnt really help in the slightest. What we do in the Newcastle
Connection is to map the pair <system, numeric id> onto a local
numeric id (group or user) and to use that for all the remote
operations performed. As a result o, files the remote system have
ownerships that are sensible for that system, which is important when
the systems are autonomous. When a user does an ls -l of a remote
system those files that are owned by the uid/gid produced are seen
(through manipulation of the "stat" information by the file server) to
be owned by the correct username and any others are shown as belonging
to a special user (usually called "remote") so as to indicate that
"These files exist, but the ownership information would not make sense
to you". The reason for this is that the Newcastle Connection ensures
that a user's local environment appears to extend to all the remote
machines so extraneous information is not allowed to percolate through
in this way. It would be possible to do a more complete inverse
mapping so that files that were owned by uids for which there was a
mapping to the user's local system were seen to belong to the
appropriate local users, but there has been no demand for this from
users so it has not been fully implemented (Tests showed that it can
be SLOOOOOOOOOW, and there are severe problems with inverting many ->
one mappings correctly). If you wish to find out who *really* owns a
file, the NC provides you with a facility to escape from your local
environment and run remotely as though you were a user on the remote
machine so you can run "ls -l" in this way and find out. (N.B.  this
is a special form of remote execution, the normal NC remote execution
does not allow you to escape from your local environment. It is also
true remote execution, NOT remote demand paging)

    In general user mapping in UN*X is a mess because of the
second-class nature of uids and gids. What we need are full pathnames
for everything.....

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Lindsay F. Marshall, Computing Lab., U of Newcastle upon Tyne, Tyne & Wear, UK
  ARPA  : lindsay%cheviot.newcastle.ac.uk at ucl-cs.arpa
  JANET : lindsay at uk.ac.newcastle.cheviot
  UUCP  : <UK>!ukc!cheviot!lindsay
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