Understanding direct mounts & ghosting

Understanding direct mounts & ghosting

[matt]

I am attempting to use direct mounts with autofs4 and either I'm doing 
something wrong or I'm expecting the wrong behaviour.  Here's my 
situation.  I installed SuSE 9.0 and then downloaded and built 
autofs-4.1.0 and autofs4-2.4 kernel module.  I installed both and added 
the alias line in modules.conf, and when I do 'lsmod' I see 'autofs4' as 
the autofs module so I think I've got the kernel part right.

The reason I am trying to get direct mounts to work is so that I can 
automount /usr/local from my fileserver, however if I put the line:
     /usr/local    server:/usr/local
into my auto.direct file, then all of /usr goes away (except 
/usr/local).  So for testing purposed I changed things to use /mnt. Now 
my auto.master includes the line:
     /-    auto.direct
and the auto.direct file contains:
     /mnt/local      voorg:/usr/local

Once I start the automounter I see the following as part of the output 
of the mount command:

automount(pid27283) on /mnt type autofs 
(rw,fd=5,pgrp=27279,minproto=2,maxproto=4)

and my test directory (/mnt/local.orig) is no longer visible.  If I then 
cd to /mnt/local the mount command shows:

automount(pid27283) on /mnt type autofs 
(rw,fd=5,pgrp=27279,minproto=2,maxproto=4)
voorg:/usr/local on /mnt/local type nfs (rw,addr=192.168.222.5)

So the automount does appear to be working; but not as I expect a direct 
mount to work based on my experience with Solaris (and HPUX).  My 
expecataion is that I should see /mnt/local as the automount point (i.e. 
"automount(pid27238) on /mnt/local type autofs ...") instead of /mnt. 
Is this the expected behavior or am I missing something?

With regards to ghosting, I have another map (auto.nfs) that's mounted 
on /nfs and, as I understand ghosting, I should be able to do:
     ls /nfs
and see a list of mountable directories (i.e. the contents of the 
auto.nfs map) as a result.  I don't.  All I see is . and .. (presuming 
of coure that I haven't cd'd to any of the mount-points).

Anything you can offer to help me understand what's happening would be 
greatly appreciated.  And if I can provide additional info about my 
setup, please let me know.

Thanks much,
Matt

Re: Understanding direct mounts & ghosting

[Ian Kent]

On Wed, 10 Mar 2004, matt wrote:

> 
> So the automount does appear to be working; but not as I expect a direct 
> mount to work based on my experience with Solaris (and HPUX).  My 
> expecataion is that I should see /mnt/local as the automount point (i.e. 
> "automount(pid27238) on /mnt/local type autofs ...") instead of /mnt. 
> Is this the expected behavior or am I missing something?

Unfortuneatly, this is the way it is now.

It's been done like that largely because of the limitation on the number 
of anonymous mounts (ie. autofs, NFS etc.) in the kernel.

It is possible to enhance the kernel module to provide this functionality 
but is a large piece of work so don't expect it any time soon.

Further, there are people working on alternate designs but I have no idea 
how those efforts are going.

> 
> With regards to ghosting, I have another map (auto.nfs) that's mounted 
> on /nfs and, as I understand ghosting, I should be able to do:
>      ls /nfs
> and see a list of mountable directories (i.e. the contents of the 
> auto.nfs map) as a result.  I don't.  All I see is . and .. (presuming 
> of coure that I haven't cd'd to any of the mount-points).

At the moment the default is for directories not to be browsable so you 
need to request it as an option in either the start script or in the 
master map.

Ian