Linux NFS-HOWTO - improvement to Troubleshooting permission denied
Subsystems (2)
Thank you for the NFS howto (last modified 2006). Please add further diagnostics to section:
=> "I do not have permission to access files on the mounted volume"
http://nfs.sourceforge.net/nfs-howto/ar01s07.html#pemission_issues
The error condition "Permission denied" also happens in certain NFS (client/server) combinations and the workaround is to add additional mount parameter at client:
sec=sys
Please add this to the "#pemission_issues" (tag the word seems to have a small typo).
See reported incidents:
http://thread.gmane.org/gmane.linux.debian.user/333162 http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=492970
Jari
----
CC: team http://sourceforge.net/projects/nfs
You're all in CC, as I did not know who is responsible for updating the NFS-HOWTO at sourceforge.
A message that is not in the archive (sent off-list or not yet received): [email protected]
Hi Jari-
Quoted 7 lines · Jari Aalto
Thank you for the NFS howto (last modified 2006). Please add further diagnostics to section:
=> "I do not have permission to access files on the mounted volume"
http://nfs.sourceforge.net/nfs-howto/ar01s07.html#pemission_issues
Quoted 8 lines
The error condition "Permission denied" also happens in certain NFS (client/server) combinations and the workaround is to add additional mount parameter at client:
sec=sys
Please add this to the "#pemission_issues" (tag the word seems to have a small typo).
This is a known bug in nfs-utils 1.1.3 when used with older client kernels that do not support text-based mounts.
Seems like an esoteric (ie not widespread) problem, but I could easily be wrong about that.
Signature · 1 line
Chuck Lever
A message that is not in the archive (sent off-list or not yet received): 76bd70e30808250841v4e73c576qc1e68c85d88bb989-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org
Quoted 16 lines · Chuck Lever
Hi Jari-
Quoted 13 lines · Jari Aalto
Thank you for the NFS howto (last modified 2006). Please add further diagnostics to section:
=> "I do not have permission to access files on the mounted volume"
http://nfs.sourceforge.net/nfs-howto/ar01s07.html#pemission_issuesThe error condition "Permission denied" also happens in certain NFS (client/server) combinations and the workaround is to add additional mount parameter at client:
sec=sys
Quoted 8 lines
Quoted 2 lines
Please add this to the "#pemission_issues" (tag the word seems to have a small typo).
This is a known bug in nfs-utils 1.1.3 when used with older client kernels that do not support text-based mounts.
Seems like an esoteric (ie not widespread) problem, but I could easily be wrong about that.
People should be able to upgrade nfs-utils without upgrading their kernel!
The referenced debian bug report:
http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=492970
claims the first bad commit is a server-side commit that itself seems to claim to work around a problem? ("For mountd, it does not advertise AUTH_NULL anymore. This is necessary to avoid backward compatibility issue. If AUTH_NULL appears in the list, either the new or the old client will choose that over AUTH_SYS.")
Did we ever find the actual root cause?
--b.
Some CC's corrected.
Quoted 21 lines · J. Bruce Fields
Quoted 20 lines · Chuck Lever
Hi Jari-
Quoted 16 lines · Jari Aalto
Thank you for the NFS howto (last modified 2006). Please add further diagnostics to section:
=> "I do not have permission to access files on the mounted
volume"
http://nfs.sourceforge.net/nfs-howto/ar01s07.html#pemission_issuesThe error condition "Permission denied" also happens in certain NFS (client/server) combinations and the workaround is to add additional mount parameter at client:
sec=sys
Please add this to the "#pemission_issues" (tag the word seems to have a small typo).
Quoted 8 lines
Quoted 5 lines
This is a known bug in nfs-utils 1.1.3 when used with older client kernels that do not support text-based mounts.
Seems like an esoteric (ie not widespread) problem, but I could easily be wrong about that.
People should be able to upgrade nfs-utils without upgrading their kernel!
Of course. But Bugs Happen. I'm not implying that nfs-utils 1.1.3 requires a kernel upgrade, but merely describing the conditions where the issue appears.
In fact, you may recall a recent and rather protracted e-mail conversation where we determined that the text-based NFS mount implementation is not working correctly in this case either.
Quoted 11 lines
The referenced debian bug report:
http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=492970claims the first bad commit is a server-side commit that itself seems to claim to work around a problem? ("For mountd, it does not advertise
AUTH_NULLanymore. This is necessary to avoid backward compatibility issue. IfAUTH_NULLappears in the list, either the new or the old client will choose that overAUTH_SYS.")Did we ever find the actual root cause?
The bad commit does not live up to the comments it introduced, which claim that the legacy mount command will skip AUTH_NULL as a default if it receives it in the auth flavor list from mountd. I haven't verified this, but otherwise, yes, we have an RCA.
I copied the patch author of record, [email protected], on the recent discussion, but we haven't heard any response. I think we will need to fix this ourselves. IMO the proper fix is to eliminate the possibility that the client will ever use AUTH_NULL unless "sec=null" is explicitly specified on the mount command line, then to get nfs-utils 1.1.4 posted with this fix.
If I may also observe: the bad commit attempts to change both server-side and client-side behavior in one go. Hindsight suggests the changes to nfsmount.c and mountd.c should have occurred in two separate commits so that automated bisection and surgical reversion are possible.
This reminds us again that we have an exponentially expanding test matrix for nfs-utils, especially considering the backwards-compatibility requirements. I would love to see significant test resources committed in this area.
Signature · 2 lines
Chuck Lever chuck[dot]lever[at]oracle[dot]com
Quoted 14 lines · Chuck Lever
Quoted 13 lines · Jari Aalto
Thank you for the NFS howto (last modified 2006). Please add further diagnostics to section:
=> "I do not have permission to access files on the mounted volume"
http://nfs.sourceforge.net/nfs-howto/ar01s07.html#pemission_issuesThe error condition "Permission denied" also happens in certain NFS (client/server) combinations and the workaround is to add additional mount parameter at client:
sec=sys
Quoted 8 lines
Quoted 2 lines
Please add this to the "#pemission_issues" (tag the word seems to have a small typo).
This is a known bug in nfs-utils 1.1.3 when used with older client kernels that do not support text-based mounts.
Seems like an esoteric (ie not widespread) problem, but I could easily be wrong about that.
Please add the tip, although the bug may be fixed in later NFS releases. There are great deal of hosts running old versions whose admins scratch they head and seek for guidance from the HOWTO.
Mentioning "sec=sys" would have saved me countless of hours tracing what was wrong in my setup[1]. Without to Bob <grantura <at> spamcop.net> and his knowledge about Debian bug, I would never had resolved the issue in decent time.
Jari
[1]
"NFS and no_root_squash - cannot write as root - permission denied"
http://thread.gmane.org/gmane.linux.debian.user/333162