Ian,

Thanks for your reply, I think from what you say I am indeed getting the
expected results. I read earlier about the autofs bug, I have 2 systems
(i386) running 2.6.18-53.1.14.el5, which still exhibit this behavior,
however my x64's are ok (same kernel). I think I also read that the
patch does not go live until RHEL 5.2. Since these only get booted after
a kernel update or once a year (just because I can!), the problem does
not really have any impact. The other odd behavior on the x64 machines,
maybe related is that for some time after install they could not cd
~user1. However this morning they can!

Thanks again,

Neil.

Ian Kent wrote:
> On Tue, 2008-04-15 at 11:11 +0100, Neil Marjoram wrote:
>> OK I have just installed 5.1 on 4 machines, one of which is my file
>> server, running ldap, samba etc. The installs are from fresh, but I am
>> using the old configs for NFS and autofs from RHEL 4.
>
> Make sure you update the kernel.
> There was a known problem where a couple of autofs patches missed in the
> initial release kernel. You can tell if you're seeing this problem as
> the first attempt to automount a directory will return a fail but the
> mount will happen.
>
>> All my servers use autofs to mount user directories from the one central
>> file server and all seems fine. Last night I completed the final upgrade
>> to the main file server, all is working just about fine, but I notice
>> that df does not show any of the filesystems mounted with autofs on the
>> file server, however cat /proc/mounts shows all the mounted directories
>> correctly. df -a also shows the directories mounted!
>>
>> I can only imagine that this is a new feature so df does not show autofs
>> mounted from the local machine.
>>
>> Am I missing something?
>
> I'm not sure about the output of df for other than for the autofs
> mounts, I would expect it to show the other mounts. The autofs file
> system mounts aren't done using mount in version 5 so they shouldn't
> normally show up in df output.
>
> To quote myself responding to a similar question on the autofs list:
>
> There are a few reasons.
>
> The foremost reason is because version 5 uses lots of mounts as
> triggers, for direct mounts and for the lazy mount/expire of trees of
> mounts (aka the multi-mounts and the hosts map). If they were added to
> the mtab this would lead to considerable confusion. And if you've used a
> system that does add these to the mtab (such as old versions of AIX) and
> your map had, even just a few hundred direct mounts, you would
> understand how annoying it is. I guess we could use a pseudo mount
> option, like "hide", so the entries aren't displayed (but that doesn't
> really help with the locking issues below).
>
> There is also the issue of mtab locking, under heavy mount activity,
> leading to mtab corruption, which we've seen often in the past. Not
> using the mtab for autofs mounts themselves substantially reduces the
> pressure on mtab locking.
>
> Finally there's the issue of scanning the mtab which I need to do fairly
> often when checking if something is mounted. A few hundred entries isn't
> that bad but the number of entries can order in the thousands for quite
> a few users which leads to performance problems and aggravates the
> locking issues.
>
> Ian
>
>
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--
Neil Marjoram
Systems Manager
Adastral Park Campus
University College London
Ross Building
Adastral Park
Martlesham Heath
Ipswich - Suffolk
IP5 3RE

Tel: 01473 663711
Fax: 01473 635199


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