automount 4.1 / mount issues and possible workarounds

automount 4.1 / mount issues and possible workarounds

[Anthony Menasse]

Hi,

I was hoping for some feedback on wether the following actions are 
appropriate to fix the issues we are having with automount /mount.  I 
haven't explained the problems in detail, but from reading the mailing 
list and other sources they seem like fairly common issues. I just want 
to make sure my proposed fixes make sense. Im guessing a lot of this has 
been discussed many times before on this list, but i just wanted some 
confirmation that i am on the right track (or not). Any advice would be 
greatly appreciated.


Setup:

A bunch of NFS servers running a mixture of  RH Enterprise 4, Enterprise 
3 and X/OS linux4 and a bunch of Fedora Core 3 clients running a non 
Fedora built 2.6.11.7 kernel. 

The automount update i am looking at installing is the latest  automount 
package from FC5 (4.1.4 Release 33) rebuilt for FC3 (which seems to work 
ok after some initial testing on a single box)

I want to avoid updating the kernel at this point.

Not sure about my strategy about updating 'mount', would you recommend 
getting the latest source or will an older package from FC3 do? In other 
words are there still serious issues with mount which mean i should be 
running the latest source or are the issues such as overriding RPC 
timeout values and locking issues with mtab only an issue with ancient 
versions of mount?

Issue 1:


nfs: mount failure chop:/export/home/rsp on /home/rsp

I believe this is due to automount using a mount  retry value of 0 and  
dodgy versions of mount overriding the default RPC timeout from 
60seconds to 0.7 seconds so the attempt times out too quickly

References:

http://nfsworld.blogspot.com/2005/03/automounter-tuning.html

http://www.mail-archive.com/autofs@linux.kernel.org/msg05281.html


Possible Fix:

I want to fix this by using --retry=2 in the auto.master file, and 
update mount where i can (i want to do both as i can't update mount on 
every machine/ platform right now)

Issue 2:

When accessing an unmounted automount mount point the automounter will 
complain that the directory is already mounted (even though it isn't!)

You may get something like this in the log / console.

BUG: <dir> already mounted

I think this is due to a corrupt mtab file due to the  race /locking 
issues with older versions of mount
 
Possible Fix:

I want to update mount where i can , and link /etc/mtab to /proc/mount . 
(Are there any issues with having mtab as a link to /proc/mounts?)


Issue 3:

Wierd errors in the logs about attempts to mount files:

Jan 20 18:45:36 glass automount[28315]: mount(nfs): nfs: mount failure 
hassan:/export/home/rsp/.sitecshrc on /home/rsp/.sitecshrc

The initial mount is failing due to the issues described above. However 
the lookup is continued for the entire path

I think i might ignore this issue until i can upgrade the kernel on the 
clients and do more testing as it seems to be related to issue 2.


thankyou if you have actually read this far:)


Cheers
Anthony


-- 
anthony menasse
systems administrator | anthony.menasse@rsp.com.au
rising sun pictures | www.rsp.com.au
direct line +61 2 9384 4572

Re: automount 4.1 / mount issues and possible workarounds

[Ian Kent]

On Fri, 2007-02-23 at 12:48 +1100, Anthony Menasse wrote:
> Hi,
> 
> I was hoping for some feedback on wether the following actions are 
> appropriate to fix the issues we are having with automount /mount.  I 
> haven't explained the problems in detail, but from reading the mailing 
> list and other sources they seem like fairly common issues. I just want 
> to make sure my proposed fixes make sense. Im guessing a lot of this has 
> been discussed many times before on this list, but i just wanted some 
> confirmation that i am on the right track (or not). Any advice would be 
> greatly appreciated.
> 
> 
> Setup:
> 
> A bunch of NFS servers running a mixture of  RH Enterprise 4, Enterprise 
> 3 and X/OS linux4 and a bunch of Fedora Core 3 clients running a non 
> Fedora built 2.6.11.7 kernel. 
> 
> The automount update i am looking at installing is the latest  automount 
> package from FC5 (4.1.4 Release 33) rebuilt for FC3 (which seems to work 
> ok after some initial testing on a single box)
> 
> I want to avoid updating the kernel at this point.
> 
> Not sure about my strategy about updating 'mount', would you recommend 
> getting the latest source or will an older package from FC3 do? In other 
> words are there still serious issues with mount which mean i should be 
> running the latest source or are the issues such as overriding RPC 
> timeout values and locking issues with mtab only an issue with ancient 
> versions of mount?
> 
> Issue 1:
> 
> 
> nfs: mount failure chop:/export/home/rsp on /home/rsp
> 
> I believe this is due to automount using a mount  retry value of 0 and  
> dodgy versions of mount overriding the default RPC timeout from 
> 60seconds to 0.7 seconds so the attempt times out too quickly
> 
> References:
> 
> http://nfsworld.blogspot.com/2005/03/automounter-tuning.html
> 
> http://www.mail-archive.com/autofs@linux.kernel.org/msg05281.html
> 
> 
> Possible Fix:
> 
> I want to fix this by using --retry=2 in the auto.master file, and 
> update mount where i can (i want to do both as i can't update mount on 
> every machine/ platform right now)

That would be "retry=2", the "--" is used for autofs options.
Could be worth a try, yes.

> 
> Issue 2:
> 
> When accessing an unmounted automount mount point the automounter will 
> complain that the directory is already mounted (even though it isn't!)
> 
> You may get something like this in the log / console.
> 
> BUG: <dir> already mounted
> 
> I think this is due to a corrupt mtab file due to the  race /locking 
> issues with older versions of mount

Could be, yes.

>  
> Possible Fix:
> 
> I want to update mount where i can , and link /etc/mtab to /proc/mount . 
> (Are there any issues with having mtab as a link to /proc/mounts?)

Should be OK with version 4.

> 
> 
> Issue 3:
> 
> Wierd errors in the logs about attempts to mount files:
> 
> Jan 20 18:45:36 glass automount[28315]: mount(nfs): nfs: mount failure 
> hassan:/export/home/rsp/.sitecshrc on /home/rsp/.sitecshrc
> 
> The initial mount is failing due to the issues described above. However 
> the lookup is continued for the entire path
> 
> I think i might ignore this issue until i can upgrade the kernel on the 
> clients and do more testing as it seems to be related to issue 2.

Exactly.
Patches are included in the 5.0.1 tar for several kernels that help with
this problem somewhat. They usually occur after a mount fail and are
caused by the kernel continuing the lookup when it shouldn't.

Ian

automount 4.1 / mount issues and possible workarounds

[Anthony Menasse]

Hi,

I was hoping for some feedback on wether the following actions are
appropriate to fix the issues we are having with automount /mount.  I
haven't explained the problems in detail, but from reading the mailing
list and other sources they seem like fairly common issues. I just want
to make sure my proposed fixes make sense. Im guessing a lot of this has
been discussed many times before on this list, but i just wanted some
confirmation that i am on the right track (or not). Any advice would be
greatly appreciated.


Setup:

A bunch of NFS servers running a mixture of  RH Enterprise 4, Enterprise
3 and X/OS linux4 and a bunch of Fedora Core 3 clients running a non
Fedora built 2.6.11.7 kernel.

The automount update i am looking at installing is the latest  automount
package from FC5 (4.1.4 Release 33) rebuilt for FC3 (which seems to work
ok after some initial testing on a single box)

I want to avoid updating the kernel at this point.

Not sure about my strategy about updating 'mount', would you recommend
getting the latest source or will an older package from FC3 do? In other
words are there still serious issues with mount which mean i should be
running the latest source or are the issues such as overriding RPC
timeout values and locking issues with mtab only an issue with ancient
versions of mount?

Issue 1:


nfs: mount failure chop:/export/home/rsp on /home/rsp

I believe this is due to automount using a mount  retry value of 0 and
dodgy versions of mount overriding the default RPC timeout from
60seconds to 0.7 seconds so the attempt times out too quickly

References:

http://nfsworld.blogspot.com/2005/03/automounter-tuning.html

http://www.mail-archive.com/autofs@linux.kernel.org/msg05281.html


Possible Fix:

I want to fix this by using --retry=2 in the auto.master file, and
update mount where i can (i want to do both as i can't update mount on
every machine/ platform right now)

Issue 2:

When accessing an unmounted automount mount point the automounter will
complain that the directory is already mounted (even though it isn't!)

You may get something like this in the log / console.

BUG: <dir> already mounted

I think this is due to a corrupt mtab file due to the  race /locking
issues with older versions of mount

Possible Fix:

I want to update mount where i can , and link /etc/mtab to /proc/mount .
(Are there any issues with having mtab as a link to /proc/mounts?)


Issue 3:

Wierd errors in the logs about attempts to mount files:

Jan 20 18:45:36 glass automount[28315]: mount(nfs): nfs: mount failure
hassan:/export/home/rsp/.sitecshrc on /home/rsp/.sitecshrc

The initial mount is failing due to the issues described above. However
the lookup is continued for the entire path

I think i might ignore this issue until i can upgrade the kernel on the
clients and do more testing as it seems to be related to issue 2.


thankyou if you have actually read this far:)


Cheers
Anthony


-- 
anthony menasse
systems administrator | anthony.menasse@rsp.com.au
rising sun pictures | www.rsp.com.au
direct line +61 2 9384 4572