>Number:         3233
>Category:       misc
>Synopsis:       mount_union manpage underestimates the need for whiteout
>Confidential:   no
>Severity:       non-critical
>Priority:       low
>Responsible:    misc-bug-people (Misc Bug People)
>State:          open
>Class:          doc-bug
>Submitter-Id:   net
>Arrival-Date:   Wed Feb 19 15:05:01 1997
>Last-Modified:
>Originator:     Eric Fischer
>Organization:
	The University of Chicago
>Release:        1.2
>Environment:
System: NetBSD fudge 1.2 NetBSD 1.2 (FUDGE) #7: Sun Jan 19 16:26:56 CST 1997 eric@fudge:/usr/people/eric/usrsrc/sys/arch/sparc/compile/FUDGE sparc


>Description:
	The mount_union manpage claims that a union mount onto a
	file system with no whiteout support will work but will
	return EROFS if you do something that would require a
	write.  In fact the mount fails immediately, and the
	manpage gives no advice about how to fix your filesystem
	to be compatible with union mounts.
>How-To-Repeat:
	Create a file system with newfs and don't run fsck -c on
	it to upgrade it to new-style inodes.  Then try to union
	mount a directory under one of the directories on that
	file system.
>Fix:
	fsck -c the file system before attempting to do the union
	mount.  Mention in the mount_union manpage that this is
	how to make it work.

*** /usr/src/sbin/mount_union/mount_union.8	Sun Jan 14 20:00:21 1996
--- mount_union.8	Wed Feb 19 16:40:11 1997
***************
*** 182,196 ****
  .Xr unmount 2 ,
  .Xr fstab 5 ,
  .Xr mount 8 ,
! .Xr mount_null 8
  .Sh BUGS
  Without whiteout support from the filesystem backing the upper layer,
  there is no way that delete and rename operations on lower layer
  objects can be done.
! .Dv EROFS
! is returned for this kind of operations along with any others
! which would make modifications to the lower layer, such as
! .Xr chmod 1 .
  .Pp
  Running
  .Xr find 1
--- 182,202 ----
  .Xr unmount 2 ,
  .Xr fstab 5 ,
  .Xr mount 8 ,
! .Xr mount_null 8 ,
! .Xr fsck_ffs 8
  .Sh BUGS
  Without whiteout support from the filesystem backing the upper layer,
  there is no way that delete and rename operations on lower layer
  objects can be done.
! An attempt to mount a union directory under one which does not
! have whiteout support will return
! .Dv EOPNOTSUPP
! (``Operation not supported'').
! Whiteout support can be added to an existing FFS filesystem
! by using the
! .Fl c
! option of
! .Xr fsck_ffs 8 .
  .Pp
  Running
  .Xr find 1
>Audit-Trail:
>Unformatted: