Subject: Re: union & null fs problem?
To: Kazufumi-MIT-Mitani <>
From: Hauke Fath <hauke@Espresso.Rhein-Neckar.DE>
List: current-users
Date: 02/10/1998 19:36:19
At 3:23 Uhr +0100 10.02.1998, Kazufumi-MIT-Mitani wrote:

># mount -r /dev/cd0a /cdrom
># mount -t union -o -b /cdrom /mnt/cdrom
># add somefile to /mnt/cdrom/foo/baa
># mkisofs -R -o /mnt/CD /mnt/cdrom
>then kernel panic.


># mount -t null /mnt/src /usr/src #(current-src directory)
>then, using 2 window,
>a) config A;cd ../compile/A;make depend;make
>b) config B;cd ../compile/B;make depend;make
>Doing a) and b) simultaneously, both 'make depend' locked up
>with D+ state, and I reboot my box, it says can't umount /usr/src.


>Is union and null file system really STABLE ??

Sigh. Less than ever.

See e.g. kern/4927. Besides that, unionfs is extremely sensitive to
simultaneous accesses (your case 2.) and intensive use (your case 1.).

What a pity -- it makes a neat poor man's version control...


"It's never straight up and down"     (DEVO)