Re: the umount() saga for regular linux desktop users

[Adrian Bunk <bunk@stusta.de>]

On Sun, Jan 02, 2005 at 01:38:29PM +0100, Bodo Eggert wrote:
> Andy Lutomirski wrote:
> 
> > I have this complaint too, and MNT_DETACH doesn't really do it.
> > Sometimes I want to "unmount cleanly, damnit, and I don't care if
> > applications that are currently accessing it lose data."  Windows can do
> > this, and it's _useful_.
> 
> I have an additional feature request: The umount -l will currently not work
> for unmounting the cwd of something like the midnight commander without
> closing it. On the other hand, rmdiring the cwd of running application
> works just fine.

A rm does not actually remove things that are still accessed.

As an example, do the following (1 and 2 are shells, cdimage is a full
CD image):

1> less cdimage
2> df .
2> rm cdimage
2> df . 
1> q (quit less)
2> df .

> Maybe it's possible to extend the semantics of umount -l to change all
> cwds under that mountpoint to be deleted directories which will no
> longer cause the mountpoint to be busy (e.g. by redirecting them to a
> special inode on initramfs). Most applications can cope with that (if
> not, they're buggy), and it will do 90% of the usural cases while still
> avoiding data loss.
>...

If the appication of a user was writing some important output to a file 
on the NFS mount you want to umount there will be data loss...

If you _really_ want to umount something still accessed by applications 
simply kill all applications with "fuser -k".

cu
Adrian

-- 

       "Is there not promise of rain?" Ling Tan asked suddenly out
        of the darkness. There had been need of rain for many days.
       "Only a promise," Lao Er said.
                                       Pearl S. Buck - Dragon Seed