DFS with unix extensions or mfsymlinks/SFU

DFS with unix extensions or mfsymlinks/SFU

[Tobias Doerffel]

Hi,

we recently deployed a DFS setup based on Samba 4. Things are working well on Windows computers while we have some troubles with our Linux terminal servers.

Our company's DFS tree is mounted at /dfs using sec=krb and the multiuser option. As soon as there are DFS links we get the famous

ls: cannot read symbolic link FOOBAR: Object is remote

message. However we can chdir into the directory (and display its contents) even though it sometimes doesn't work immediately. When I however disable unix extensions (-o nounix) I don't have these issues and DFS referrals get resolved/mounted immediately, that's why we currently use this option. However disabling unix extensions is not an option long term as our users need software which creates e.g. pipes/FIFOs, does file locking etc. and worked well before (with OpenAFS). This could be achieved by using the «sfu» option. But if I enable SFU support, I can neither create symlinks nor use the mfsymlinks mount option. So whatever approach I chose, there's always something not working properly.

Do you have any advice? Is there any reason why SFU does not work in conjunction with MFSymLinks?

More information:

Mount options used:
- mostly working DFS setup without unix extensions: sec=krb5,nounix,multiuser,mfsymlinks,dir_mode=0700,file_mode=0700,noserverino,cache=strict,mapchars,rsize=16777216,wsize=16777216,nobrl

- Simple test setup with unix extensions:
sec=krb5,multiuser,cache=strict

System: Ubuntu 12.04.4 LTS x86_64
Kernel version: 3.13.6 (current  Ubuntu 14.04 kernel)
CIFS utils: 6.3
Keyutils: 1.5.9

# grep CIFS /boot/config-3.13.0-21-generic 
CONFIG_CIFS=m
CONFIG_CIFS_STATS=y
# CONFIG_CIFS_STATS2 is not set
CONFIG_CIFS_WEAK_PW_HASH=y
CONFIG_CIFS_UPCALL=y
CONFIG_CIFS_XATTR=y
CONFIG_CIFS_POSIX=y
CONFIG_CIFS_ACL=y
CONFIG_CIFS_DEBUG=y
# CONFIG_CIFS_DEBUG2 is not set
CONFIG_CIFS_DFS_UPCALL=y
CONFIG_CIFS_SMB2=y
CONFIG_CIFS_FSCACHE=y


Thank you in advance and best regards

Tobias Doerffel


--
Dipl.-Inf. Tobias Doerffel

-----------------------------------------------
EDC Electronic Design Chemnitz GmbH
Technologie-Campus 4, 09126 Chemnitz

Geschäftsführer: Dr.-Ing. Steffen Heinz
                 Dipl.-Ing. André Lange
Tel.:            +49 371 52 45 90
Fax.:            +49 371 52 45 910
E-Mail:          info-2LT3hlbiLj/X2ID+q72mRQ@public.gmane.org

Sitz der Gesellschaft: Chemnitz
HRB 23986, Amtsgericht Chemnitz
USTID: DE258181725
-----------------------------------------------

Re: DFS with unix extensions or mfsymlinks/SFU

[Sachin Prabhu]

On Fri, 2014-04-04 at 12:44 +0200, Tobias Doerffel wrote:
> Hi,
> 
> we recently deployed a DFS setup based on Samba 4. Things are working well on Windows computers while we have some troubles with our Linux terminal servers.
> 
> Our company's DFS tree is mounted at /dfs using sec=krb and the multiuser option. As soon as there are DFS links we get the famous
> 
> ls: cannot read symbolic link FOOBAR: Object is remote
> 
> message. However we can chdir into the directory (and display its contents) even though it sometimes doesn't work immediately. When I however disable unix extensions (-o nounix) I don't have these issues and DFS referrals get resolved/mounted immediately, that's why we currently use this option. However disabling unix extensions is not an option long term as our users need software which creates e.g. pipes/FIFOs, does file locking etc. and worked well before (with OpenAFS). This could be achieved by using the «sfu» option. But if I enable SFU support, I can neither create symlinks nor use the mfsymlinks mount option. So whatever approach I chose, there's always something not working properly.
> 
> Do you have any advice? Is there any reason why SFU does not work in conjunction with MFSymLinks?
> 

Hello Tobais,

The following patch should help you.
http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=924e3fa48c627ad45d3be9412a93df34ab0fb482

This is probably not yet included in the kernel you are using. Maybe you
can try recompiling your kernel with this patch included and see if it
helps you.

Regards
Sachin Prabhu

> More information:
> 
> Mount options used:
> - mostly working DFS setup without unix extensions: sec=krb5,nounix,multiuser,mfsymlinks,dir_mode=0700,file_mode=0700,noserverino,cache=strict,mapchars,rsize=16777216,wsize=16777216,nobrl
> 
> - Simple test setup with unix extensions:
> sec=krb5,multiuser,cache=strict
> 
> System: Ubuntu 12.04.4 LTS x86_64
> Kernel version: 3.13.6 (current  Ubuntu 14.04 kernel)
> CIFS utils: 6.3
> Keyutils: 1.5.9
> 
> # grep CIFS /boot/config-3.13.0-21-generic 
> CONFIG_CIFS=m
> CONFIG_CIFS_STATS=y
> # CONFIG_CIFS_STATS2 is not set
> CONFIG_CIFS_WEAK_PW_HASH=y
> CONFIG_CIFS_UPCALL=y
> CONFIG_CIFS_XATTR=y
> CONFIG_CIFS_POSIX=y
> CONFIG_CIFS_ACL=y
> CONFIG_CIFS_DEBUG=y
> # CONFIG_CIFS_DEBUG2 is not set
> CONFIG_CIFS_DFS_UPCALL=y
> CONFIG_CIFS_SMB2=y
> CONFIG_CIFS_FSCACHE=y
> 
> 
> Thank you in advance and best regards
> 
> Tobias Doerffel
> 
> 
> --
> Dipl.-Inf. Tobias Doerffel
> 
> -----------------------------------------------
> EDC Electronic Design Chemnitz GmbH
> Technologie-Campus 4, 09126 Chemnitz
> 
> Geschäftsführer: Dr.-Ing. Steffen Heinz
>                  Dipl.-Ing. André Lange
> Tel.:            +49 371 52 45 90
> Fax.:            +49 371 52 45 910
> E-Mail:          info-2LT3hlbiLj/X2ID+q72mRQ@public.gmane.org
> 
> Sitz der Gesellschaft: Chemnitz
> HRB 23986, Amtsgericht Chemnitz
> USTID: DE258181725
> -----------------------------------------------
> 
> 
> --
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AW: DFS with unix extensions or mfsymlinks/SFU

[Tobias Doerffel]

Hi Sachin,

thank you very much for your response! In the meanwhile we abandoned DFS and use a single all-in-one share instead (which works flawlessly). Maybe one day we will switch back to DFS and the mentioned patch will be part of recent distro kernels.

Best regards

Tobias