NFS Client How-ToLast Updated: June 18, 2012 |
Table of Contents |
|
Adding NFS to the NuttX Configuration |
The NFS client is easily added to your configuration:
You simply need to add CONFIG_NFS
to your nuttx/.config
file.
There are, however, a few dependencies on other system settings:
CONFIG_NFILE_DESCRIPTORS > 0
. You must include support for file descriptors.
CONFIG_DISABLE_MOUNTPOINT=n
. You must include support for mount points in the pseudo-file system.
CONFIG_NET=y
. General networking support.
CONFIG_NET_UDP=y
. Support for UDP.
Mount Interface |
A low-level, C-callable interface is provided to mount a file system.
That interface is called mount()
and is mentioned in the porting guide
and is prototyped in the header file include/sys/mount.h
:
int mount(const char *source, const char *target, const char *filesystemtype, unsigned long mountflags, const void *data);
Synopsis:
mount()
attaches the filesystem specified by the source
block device name into the root file system at the path specified by target
.
Input Paramters:
source
. A null-terminated string providing the fill path to a block driver in the NuttX pseudo-file system.
target
. The location in the NuttX pseudo-file system where the volume will be mounted.
filesystemtype
. A string identifying the type of file system to use.
mountflags
. Various flags that can be used to qualify how the file system is mounted.
data
. Opaque data that is passed to the file system with the mount occurs.
Returned Values
Zero is returned on success; -1 is returned on an error and errno
is set appropriately:
EACCES
.
A component of a path was not searchable or mounting a read-onlyfilesystem was attempted without giving the MS_RDONLY
flag.
EBUSY
.
source
is already mounted.
EFAULT
.
One of the pointer arguments points outside the user address space.
EINVAL
.
source
had an invalid superblock.
ENODEV
.
filesystemtype
not configured
ENOENT
.
A pathname was empty or had a nonexistent component.
ENOMEM
.
Could not allocate a memory to copy filenames or data into.
ENOTBLK
.
source
is not a block device
This same interface can be used to mount a remote, NFS file system using some special parameters.
The NFS mount differs from the normal file system mount in that: (1) there is no block driver for the NFS file system, and (2) special parameters must be passed as data
to describe the remote NFS server.
Thus the following code snippet might represent how an NFS file system is mounted:
#include <sys/mount.h> #include <nuttx/fs/nfs.h> struct nfs_args data; char *mountpoint; ret = mount(NULL, mountpoint, string "nfs", 0, (FAR void *)&data);
NOTE that: (1) the block driver paramter is NULL
.
The mount()
is smart enough to know that no block driver is needed with the NFS file system.
(2) The NFS file system is identified with the simple string "nfs"
(3) A reference to struct nfs_args
is passed as an NFS-specific argument.
The NFS-specific interface is described in the file include/nuttx/fs/nfs.h
.
There you can see that struct nfs_args
is defined as:
struct nfs_args { uint8_t addrlen; /* Length of address */ uint8_t sotype; /* Socket type */ uint8_t flags; /* Flags, determines if following are valid: */ uint8_t timeo; /* Time value in deciseconds (with NFSMNT_TIMEO) */ uint8_t retrans; /* Times to retry send (with NFSMNT_RETRANS) */ uint16_t wsize; /* Write size in bytes (with NFSMNT_WSIZE) */ uint16_t rsize; /* Read size in bytes (with NFSMNT_RSIZE) */ uint16_t readdirsize; /* readdir size in bytes (with NFSMNT_READDIRSIZE) */ char *path; /* Server's path of the directory being mount */ struct sockaddr_storage addr; /* File server address (requires 32-bit alignment) */ };
NFS Mount Command |
The NuttShell (NSH) also supports a command called nfsmount
that can be used to mount a remote file system via the NSH command line.
Command Syntax:
nfsmount <server-address> <mount-point> <remote-path>
Synopsis.
The nfsmount
command mounts a network file system in the NuttX pseudo filesystem.
The nfsmount
will use NFSv3 UDP protocol to mount the remote file system.
Command Line Arguments.
The nfsmount
takes three arguments:
<server-address>
is the IP address of the server exporting the file system you wish to mount.
This implementation of NFS for the NuttX RTOS is only for a local area network, so the server and client must be in the same network.
<mount-point >
is the location in the NuttX pseudo filesystem where the mounted volume will appear.
This mount point can only reside in the NuttX pseudo filesystem.
By convention, this mount point is a subdirectory under /mnt
.
The mount command will create whatever pseudo directories that may be needed to complete the full path (but the full path must not already exist).
<remote-path>
is the file system /
directory being exported from server.
This /
directory must have been configured for exportation on the server before when the NFS server was set up.
After the volume has been mounted in the NuttX pseudo filesystem, it may be access in the same way as other objects in the file system.
Example.
Suppose the the NFS server has been configured to export the directory /export/shared
.
The the following command would mount that file system (assuming that the target also has privileges to mount the file system).
NuttShell (NSH) nsh> ls /mnt /mnt: nsh: ls: no such directory: /mnt nsh> nfsmount 10.0.0.1 /mnt/nfs /export/shared nsh> ls -l /mnt/nfs /mnt/nfs: drwxrwxrwx 4096 .. drwxrwxrwx 4096 testdir/ -rw-rw-rw- 6 ctest.txt -rw-r--r-- 15 btest.txt drwxrwxrwx 4096 . nsh> echo "This is a test" >/mnt/nfs/testdir/testfile.txt nsh> ls -l /mnt/nfs/testdir /mnt/nfs/testdir: -rw-rw-rw- 21 another.txt drwxrwxrwx 4096 .. drwxrwxrwx 4096 . -rw-rw-rw- 16 testfile.txt nsh> cat /mnt/nfs/testdir/testfile.txt This is a test
Configuring the NFS server (Ubuntu) |
Setting up the server will be done in two steps: First, setting up the configuration file for NFS, and then starting the NFS services. But first, you need to install the nfs server on Ubuntu with the these two commands:
# sudo apt-get install nfs-common # sudo apt-get install nfs-kernel-server
After that, we need to make or choose the directory we want to export from the NFS server.
In our case, we are going to make a new directory called /export
.
# sudo mkdir /export
It is important that /export
directory allow access to everyone (777 permissions) as we will be accessing the NFS share from the client with no authentication.
# sudo chmod 777 /export
When all this is done, we will need to edit the configuration file to set up an NFS server: /etc/exports
.
This file contains a list of entries;
each entry indicates a volume that is shared and how it is shared.
For more information for a complete description of all the setup options for this file you can check in the man pages (man export
).
/etc/exports
will typically look like this:
directory machine1(option11,option12)
So for our example we export
/export 10.0.0.2(rw)
In our case we are using all the default options except for the ro
that we replaced with rw
so that our client will have read and write access to the directory that we are exporting.
# sudo /etc/init.d/nfs-kernel-server startNote: If you later decide to add more NFS exports to the /etc/exports file, you will need to either restart NFS daemon or run command exportfs.
# sudo /etc/init.d/nfs-kernel-server start
Or
# exportfs -ra
Now we can check if the export directory and our mount point is properly set up.
# sudo showmount -e # sudo showmount -a
And also we can verify if NFS is running in the system with:
# rpcinfo –p program vers proto port 100000 2 tcp 111 portmapper 100000 2 udp 111 portmapper 100011 1 udp 749 rquotad 100011 2 udp 749 rquotad 100005 1 udp 759 mountd 100005 1 tcp 761 mountd 100005 2 udp 764 mountd 100005 2 tcp 766 mountd 100005 3 udp 769 mountd 100005 3 tcp 771 mountd 100003 2 udp 2049 nfs 100003 3 udp 2049 nfs 300019 1 tcp 830 amd 300019 1 udp 831 amd 100024 1 udp 944 status 100024 1 tcp 946 status 100021 1 udp 1042 nlockmgr 100021 3 udp 1042 nlockmgr 100021 4 udp 1042 nlockmgr 100021 1 tcp 1629 nlockmgr 100021 3 tcp 1629 nlockmgr 100021 4 tcp 1629 nlockmgr
Now your NFS sever is sharing /export
directory to be accessed.