DFS with unix extensions or mfsymlinks/SFU

[Tobias Doerffel]

Hi,

we recently deployed a DFS setup based on Samba 4. Things are working w=
ell on Windows computers while we have some troubles with our Linux ter=
minal servers.

Our company's DFS tree is mounted at /dfs using sec=3Dkrb and the multi=
user 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 conte=
nts) even though it sometimes doesn't work immediately. When I however =
disable unix extensions (-o nounix) I don't have these issues and DFS r=
eferrals get resolved/mounted immediately, that's why we currently use =
this option. However disabling unix extensions is not an option long te=
rm as our users need software which creates e.g. pipes/FIFOs, does file=
locking etc. and worked well before (with OpenAFS). This could be achi=
eved by using the =ABsfu=BB option. But if I enable SFU support, I can =
neither create symlinks nor use the mfsymlinks mount option. So whateve=
r 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 co=
njunction with MFSymLinks?

More information:

Mount options used:
- mostly working DFS setup without unix extensions: sec=3Dkrb5,nounix,m=
ultiuser,mfsymlinks,dir_mode=3D0700,file_mode=3D0700,noserverino,cache=3D=
strict,mapchars,rsize=3D16777216,wsize=3D16777216,nobrl

- Simple test setup with unix extensions:
sec=3Dkrb5,multiuser,cache=3Dstrict

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=20
CONFIG_CIFS=3Dm
CONFIG_CIFS_STATS=3Dy
# CONFIG_CIFS_STATS2 is not set
CONFIG_CIFS_WEAK_PW_HASH=3Dy
CONFIG_CIFS_UPCALL=3Dy
CONFIG_CIFS_XATTR=3Dy
CONFIG_CIFS_POSIX=3Dy
CONFIG_CIFS_ACL=3Dy
CONFIG_CIFS_DEBUG=3Dy
# CONFIG_CIFS_DEBUG2 is not set
CONFIG_CIFS_DFS_UPCALL=3Dy
CONFIG_CIFS_SMB2=3Dy
CONFIG_CIFS_FSCACHE=3Dy


Thank you in advance and best regards

Tobias Doerffel


--
Dipl.-Inf. Tobias Doerffel

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

Gesch=E4ftsf=FChrer: Dr.-Ing. Steffen Heinz
Dipl.-Ing. Andr=E9 Lange
Tel.: [phone]
=46ax.: [phone]
E-Mail: info-2LT3hlbiLj/X2ID+***@public.gmane.org

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

[Sachin Prabhu]

Hi,
=20
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 t=
erminal servers.

=20
Our company's DFS tree is mounted at /dfs using sec=3Dkrb and the mul=

tiuser option. As soon as there are DFS links we get the famous

=20
ls: cannot read symbolic link FOOBAR: Object is remote
=20
message. However we can chdir into the directory (and display its con=

tents) even though it sometimes doesn't work immediately. When I howeve=
r disable unix extensions (-o nounix) I don't have these issues and DFS=
referrals get resolved/mounted immediately, that's why we currently us=
e this option. However disabling unix extensions is not an option long =
term as our users need software which creates e.g. pipes/FIFOs, does fi=
le locking etc. and worked well before (with OpenAFS). This could be ac=
hieved by using the =C2=ABsfu=C2=BB 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 proper=
ly.

=20
Do you have any advice? Is there any reason why SFU does not work in =

conjunction with MFSymLinks?

=20

Hello Tobais,

The following patch should help you.
http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?=
id=3D924e3fa48c627ad45d3be9412a93df34ab0fb482

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

Regards
Sachin Prabhu

=20
- mostly working DFS setup without unix extensions: sec=3Dkrb5,nounix=

,multiuser,mfsymlinks,dir_mode=3D0700,file_mode=3D0700,noserverino,cach=
e=3Dstrict,mapchars,rsize=3D16777216,wsize=3D16777216,nobrl

=20
sec=3Dkrb5,multiuser,cache=3Dstrict
=20
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
=20
# grep CIFS /boot/config-3.13.0-21-generic=20
CONFIG_CIFS=3Dm
CONFIG_CIFS_STATS=3Dy
# CONFIG_CIFS_STATS2 is not set
CONFIG_CIFS_WEAK_PW_HASH=3Dy
CONFIG_CIFS_UPCALL=3Dy
CONFIG_CIFS_XATTR=3Dy
CONFIG_CIFS_POSIX=3Dy
CONFIG_CIFS_ACL=3Dy
CONFIG_CIFS_DEBUG=3Dy
# CONFIG_CIFS_DEBUG2 is not set
CONFIG_CIFS_DFS_UPCALL=3Dy
CONFIG_CIFS_SMB2=3Dy
CONFIG_CIFS_FSCACHE=3Dy
=20
=20
Thank you in advance and best regards
=20
Tobias Doerffel
=20
=20
--
Dipl.-Inf. Tobias Doerffel
=20
-----------------------------------------------
EDC Electronic Design Chemnitz GmbH
Technologie-Campus 4, 09126 Chemnitz
=20
Gesch=C3=A4ftsf=C3=BChrer: Dr.-Ing. Steffen Heinz
Dipl.-Ing. Andr=C3=A9 Lange
Tel.: [phone]
Fax.: [phone]
=20
Sitz der Gesellschaft: Chemnitz
HRB 23986, Amtsgericht Chemnitz
USTID: DE258181725
-----------------------------------------------
=20
=20
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[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