NFS mount error

[Sam Sharpe]

On 23 January 2010 22:17, Craig White <craigwhite at azapple.com> wrote:
> On Sat, 2010-01-23 at 13:59 -0800, Geoffrey Leach wrote:
>> I've got a simple network, systems 'A' and 'B' connected via wireless.
>> B wants to mount A's /, /home and /usr/local. The fstab entries are
>> A:/               /A                nfs       defaults        0 0
>> A:/home           /A-home           nfs       defaults        0 0
>> A:/usr/local      /A-ul             nfs       defaults        0 0
>>
>> With this, B should do the mounts at boot time, assuming A is on line,
>> which it is.
>>
>> The curious thing is that the mount of A:/ works fine. mounts of A:/
>> home and A:/usr/local fail with "mount.nfs: Unknown error 521"
>>
>> FWIW, B is running Fedora 10, while A is running up-to-date Fedora 12.
>> This worked find prior to reloading F12 on A. Presumably I've missed
>> something -- any ideas?
> ----
> at the point of having A:/ already mounted, the other mounts are
> redundant and confusing.

Actually they are not - the directories /A/home and /A/usr/local will
be blank by default, because they will not be exported with the
"nohide" option in /etc/exports. Mounting them separately might be
what the OP perceives is the solution to this.

       nohide
              This  option is based on the option of the same name provided in
              IRIX NFS.  Normally, if a server exports two filesystems one  of
              which  is  mounted  on  the  other, then the client will have to
              mount both filesystems explicitly to get access to them.  If  it
              just  mounts  the  parent, it will see an empty directory at the
              place where the other filesystem is mounted.  That filesystem is
              "hidden".

              Setting  the  nohide  option on a filesystem causes it not to be
              hidden, and an appropriately authorised client will be  able  to
              move  from  the  parent  to that filesystem without noticing the
              change.

              However, some NFS clients do not cope well with  this  situation
              as,  for  instance, it is then possible for two files in the one
              apparent filesystem to have the same inode number.

              The nohide option is currently only  effective  on  single  host
              exports.   It  does  not work reliably with netgroup, subnet, or
              wildcard exports.

The other interesting option in /etc/exports that may be worth
experimenting with is "crossmnt":

       crossmnt
              This option is similar to nohide but it makes  it  possible  for
              clients  to  move  from  the  filesystem marked with crossmnt to
              exported filesystems mounted on it.  Thus when a child  filesys-
              tem  "B" is mounted on a parent "A", setting crossmnt on "A" has
              the same effect as setting "nohide" on B.

--
Sam