kern/66829: mounting fdesc union on /dev panics 4.10-prelease#2

[Clemens Fischer]

>Number:         66829
>Category:       kern
>Synopsis:       mounting fdesc union on /dev panics 4.10-prelease#2
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    freebsd-bugs
>State:          open
>Quarter:        
>Keywords:       
>Date-Required:
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Tue May 18 12:50:15 PDT 2004
>Closed-Date:
>Last-Modified:
>Originator:     clemens fischer
>Release:        FreeBSD 4.10-PRERELEASE i386
>Organization:
none
>Environment:
System: FreeBSD spotteswoode.dnsalias.org 4.10-PRERELEASE FreeBSD
4.10-PRERELEASE #2: Fri May 14 17:12:04 CEST 2004
root at spotteswoode.dnsalias.org:/mail/freebsd/obj/mail/freebsd/RELENG_4/src/sys/n1
i386

>Description:
	with "fdesc /dev fdesc rw,union 0 0" in /etc/fstab, the machine
	won't even survive the /etc/rc.* scripts, panic with something
	like "ufs rehash..." and reboot.

>How-To-Repeat:
	behaviour is 100% reproducable, although having "noauto" in the
	fstab entry and mounting fdesc manually will let the system live
	for seconds and minutes.  DO NOT automount fdesc on a production
	machine over a ssh-connection; it won't enter multiuser!

>Fix:
	none yet.  fdesc seems unusable.

  clemens
>Release-Note:
>Audit-Trail:
>Unformatted:
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