export config

Export Path and Pseudo Configuration and Use

EXPORT and mount examples with mount_path_pseudo = false

Path			Pseudo			Tag		Mechanism	Mount
/export/test1	/export/test1	test1	v3 Path		mount -o vers=3 server:/export/test1
/export/test1	/export/test1	test1	v3 Tag		mount -o vers=3 server:test1
/export/test1	/export/test1	test1	v4 Pseudo	mount -o vers=4 server:/export/test1
/				/export/ceph1	ceph1	v3 Path		mount -o vers=3 server:/
/				/export/ceph1	ceph1	v3 Tag		mount -o vers=3 server:ceph1
/				/export/ceph1	ceph1	v4 Pseudo	mount -o vers=4 server:/export/ceph1
/				/export/ceph2	ceph2	v3 Path		not accessible
/				/export/ceph2	ceph2	v3 Tag		mount -o vers=3 server:ceph2
/				/export/ceph2	ceph2	v4 Pseudo	mount -o vers=4 server:/export/ceph2

EXPORT and mount examples with mount_path_pseudo = true

Path			Pseudo			Tag		Mechanism	Mount
/export/test1	/export/test1	test1	v3 Pseudo	mount -o vers=3 server:/export/test1
/export/test1	/export/test1	test1	v3 Tag		mount -o vers=3 server:test1
/export/test1	/export/test1	test1	v4 Pseudo	mount -o vers=4 server:/export/test1
/				/export/ceph1	ceph1	v3 Pseudo	mount -o vers=3 server:/export/ceph1
/				/export/ceph1	ceph1	v3 Tag		mount -o vers=3 server:ceph1
/				/export/ceph1	ceph1	v4 Pseudo	mount -o vers=4 server:/export/ceph1
/				/export/ceph2	ceph2	v3 Pseudo	mount -o vers=3 server:/export/ceph2
/				/export/ceph2	ceph2	v3 Tag		mount -o vers=3 server:ceph2
/				/export/ceph2	ceph2	v4 Pseudo	mount -o vers=4 server:/export/ceph2

Ganesha exports are configured somewhat more flexibly than
other NFS servers. This document is intended to help understand
the namespace aspects of Ganesha export configuration.

First, it is highly recommended that the following option be set in
the NFS_CORE_PARAM block:

    mount_path_pseudo = true;

This option will make NFS v3 and NFS v4.x mounts both use the same
server side path to reach an export, for example:

    mount -o vers=3 192.168.0.1:/export /mnt
    mount -o vers=4 192.168.0.1:/export /mnt

Without this option, NFS v3 mounts use the Path option and NFS v4.x
mounts use the Pseudo option.

The Path option instructs Ganesha where to find the export. For
the VFS FSAL, this is the location within the server's namespace.
For other FSALs, it may be the location within the filesystem
managed by that FSAL's namespace. For example, if the CEPH FSAL
is used to export an entire CephFS volume, Path would be /.

The Pseudo option instructs Ganesha where to place the export within
NFS v4's pseudo file system namespace. NFS v4 specifies the server may
construct a pseudo namespace that may not correspond to any actual
locations of exports, and portions of that pseudo filesystem may
exist only within the realm of the NFS server and not correspond
to any physical directories. Further, an NFS v4 server places all
its exports within a single namespace. It is possible to have a
single export exported as the pseudo filesystem root, but it is much
more common to have multiple exports placed in the pseudo filesystem.
With a traditional VFS, often the Pseudo location is the same as the
Path location, but again, returning to the example CephFS export
with "/" as the Path, if multiple exports are desired, the export
would likely have something else (for example /ceph) as the Pseudo
option.

An NFS v4 client can mount the root of the pseudo file system (and
in fact, under the covers this is always what happens, NFS v4 has
no special MOUNT protocol, instead, there is an operation
PUTROOTFH which instructs the server to navigate to the root of
the pseudo filesystem, from whence LOOKUP operations are used to
navigate to the directory of interest. Thus the NFS v4 mount
command:

    mount -o vers=4 192.168.0.1:/export /mnt

results in a PUTROOTFH followed by LOOKUP export, while

    mount -o vers=4 192.168.0.1:/ceph /mnt

would result in PUTROOTFH followed by LOOKUP ceph

Without the

    mount_path_pseudo = true;

option, the NFS v3 mount command to access the CephFS export would be:

    mount -o vers=3 192.168.0.1:/ /mnt

Note also that if several CephFS volumes were exported, all the
exports might have the same Path (/). Without the mount_path_pseudo
option, only the first would be accessible to NFS v3 mounts (unless
the obscure Tag export option was used).