Hello, 

I'm trying to be a good boy and use dump+restore properly to back up /usr.
 To move wd0e to wd1e, I did:

$ mount                         
/dev/wd0a on / type ffs (local)
/dev/wd0e on /usr type ffs (local)
/dev/wd0f on /usr/local/play type ffs (local)
kernfs on /kern type kernfs (local)
/dev/wd1e on /mnt type ffs (local)
$ pwd                           
/mnt
jklowden@oak.schemamania.org
$ dump 0f - /usr  |restore -xf -

per the man page.  It ends like this (hundreds of such warnings):  

Warning: `..' missing from directory ./users
Warning: `.' missing from directory ./fat_backup
Warning: `..' missing from directory ./fat_backup
Warning: `.' missing from directory ./sup
Warning: `..' missing from directory ./sup
  DUMP: 0.69% done, finished in 17:38
  DUMP: 20.71% done, finished in 0:47
  DUMP: 37.32% done, finished in 0:29
  DUMP: 66.43% done, finished in 0:11
set owner/mode for '.'? [yn] n
  DUMP: Broken pipe
  DUMP: The ENTIRE dump is aborted.
$ ls . /usr
.:
X11R6           include         lkm             pkgsrc          share
bin             lib             local           pkgsrc.tar.gz   sup
fat_backup      libdata         mdec            pkgsrc_tar.gz   users
games           libexec         pkg             sbin

/usr:
X11R6           include         lkm             pkgsrc          share
bin             lib             local           pkgsrc.tar.gz   sup
fat_backup      libdata         mdec            pkgsrc_tar.gz   users
games           libexec         pkg             sbin

What do those warnings mean?  How can '.' go missing from an extant
directory?  

Everything "seems" OK; it sure doesn't look like "The ENTIRE dump is
aborted" (the filesystem had been empty).  Why did the pipe break?  Is
that a bug?  

Perhaps ye olde dump(8) veterans have seen this before, and can explain to
the tenderfoot the ways of the dumpmasters?  

Many thanks.

--jkl