> I'd guess that /tmp is owned by group wheel, so files created in that
> directory by default are owned by group wheel, and that user `news' is

Yes /tmp was owned by group wheel and news is not a member.

/etc/mtree/4.4BSD.dist indicates that this is correct.

uname=root gname=wheel mode=01777

at least that's what I've always used.

> not in group wheel, so mv(1) is unable to change the group of the
> file.

Yet all apparently necessary ownership was correct once the mv was
completed.  Though I guess that was more the fact that /var/spool/nn
was owned by group news ?

Ok, so now /var/tmp is owned by group bin 

news:8$ touch /var/tmp/junk            
news:9$ ls -lg /var/tmp/junk
-rw-rw-r--  1 news  bin  0 Apr  2 11:47 /var/tmp/junk
news:10$ mv /var/tmp/junk /var/spool/nn 
mv: /var/spool/nn/junk: set owner/group: Operation not permitted
news:11$ ls -lg /var/spool/nn/junk 
-rw-rw-r--  1 news  news  0 Apr  2 11:47 /var/spool/nn/junk
news:12$ ls -aldg /var/tmp
drwxrwxrwt  2 root  bin  512 Apr  2 11:48 /var/tmp
news:13$ id
uid=8(news) gid=8(news) groups=8(news)

Interesting neh?

--sjg