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RHEL4 NFS read-write/read-only issue encountered



Sometime late in April we encountered a problem on RHEL5 with regards
to filesystems getting mounted with incorrect permissions. This week
we have experienced and reproduced on demand the issue on RHEL4.  The
below information uses NetApp filer syntax in the examples, but it
should have the same impact on any fileserver since this is a client-side
issue. At this time we don’t know if this a RedHat specific problem or
a Linux 2.6 kernel issue. Has anybody else with large RHEL4 installations been impacted by this issue?

  The symptoms are as follows:
    * A qtree or subdirectory is mounted on two locations with different
      NFS options
          o For example, rw and ro
    * The first directory gets mounted on the location with the correct
      options
    * All subsequent directories mounted incorrectly get the first
      directory’s options

  How to reproduce (as root):


    * mkdir /mnt1 /mnt2
    * mount filer:/vol/vol2/test /mnt1
    * mount –o ro filer:/vol/vol2/test /mnt2
    * grep filer:/vol/vol2/test /proc/mounts
          o Verify that /mnt2 is incorrectly rw
          o Do not depend on the output of the `mount` command as it
            will display incorrect information
    * touch /mnt1/blah1; touch /mnt2/blah2
          o If the directory permissions do not allow root to write, do
            this and the next two commands as a user who does have
            permission.
          o If root does not have permissions, you will get an error
            stating permission denied.
    * ls /mnt1/blah1 /mnt2/blah2
          o Verify that both files were created
    * rm /mnt1/blah1 /mnt2/blah2
    * umount /mnt1 /mnt2
    * mount –o ro filer:/vol/vol2/test /mnt2
    * mount filer:/vol/vol2/test /mnt1
    * grep filer:/vol/vol2/test /proc/mounts
          o Verify that /mnt1 is incorrectly ro
          o Do not depend on the output of the `mount` command as it
            will display incorrect information
    * touch /mnt1/blah1 /mnt2/blah2
          o Verify you got an error stating ‘Read-only file system’
            which is very different from a simple permission denied.
    * umount /mnt1 /mnt2
    * rmdir /mnt1 /mnt2


Paul Krizak                         5900 E. Ben White Blvd. MS 625
Advanced Micro Devices              Austin, TX  78741
Linux/Unix Systems Engineering      Phone: (512) 602-8775
Silicon Design Division             Cell:  (512) 791-0686





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