[cs615asa] Assignment #4 Questions

[Jan Schaumann]

Lisa Joseph <ljoseph at stevens.edu> wrote:
 
> Adding user/group in remote system:
> 1) UID exists
> error: UID is not unique
> 2)Username exists
> error: user already exists

That's fine.

> 3)GID exists
> error: GID is not unique

This shouldn't be an error -- if you wish to add a user with gid X, and
gid X already exists on the host, then that's not an error scenario.
You just add the user and the user will become a member of the already
existing group with gid X.

> 4)groupname exists
> error: group already exists

Same as above.

> >> > What happens if the group name already exists and the GIDs (local and
> >> > remote) do not match?
> >>
> >> Hmmm.  Name exists, but gid mismatch.  Let's say: use given name, ie
> >> accept different gid.
> 
> When i gave same groupname and different gid , groupadd command didnt 
> allow me to add new group since name is already existing.

Right, you shouldn't try to add a new group with an existing name and a
different gid.  You should just accept whatever gid exists on the system
for the given group name.


So what you need to do is:

for each user:
	determine name of primary group
	determine gid of primary group
	attempt to add user on remote system with that gid
		if uname already exists:
			error
		if uid already exists:
			generate a warning
			create user with different uid (ie let the
				system pick one)
		if gid does not exist already:
			create group with gid and name as on the local system
			if group name already exists:
				error

(All not explicitly mentioned 'else' statements in the above pseudo-code
are implicitly 'ok' fall-throughs.)

I think that's the easiest approach that catches most circumstances to
the satisfaction of the invoking user.  (If I'm contradicting myself
versus earlier emails, I apologize.  But it serves as a good example of
how an even simple program can have ambigous use cases and error
scenarios need to be well defined.)

-Jan
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