Add NFS How-To document
git-svn-id: svn://svn.code.sf.net/p/nuttx/code/trunk@4849 42af7a65-404d-4744-a932-0658087f49c3
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Documentation/NfsHowto.html
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Documentation/NfsHowto.html
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<html>
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<head>
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<title>NFS Client How-To</title>
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</head>
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<body background="backgd.gif">
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<hr><hr>
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<table width ="100%">
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<tr align="center" bgcolor="#e4e4e4">
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<td>
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<h1><big><font color="#3c34ec"><i>NFS Client How-To</i></font></big></h1>
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<p>Last Updated: June 18, 2012</p>
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</td>
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</tr>
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</table>
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<hr><hr>
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<table width ="100%">
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<tr bgcolor="#e4e4e4">
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<td>
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<h1>Table of Contents</h1>
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</td>
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</tr>
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</table>
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<center><table width ="80%">
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<tr>
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<td>
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<table>
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<tr>
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<td valign="top" width="22"><img height="20" width="20" src="favicon.ico"></td>
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<td>
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<a href="#mountinterface">Mount Interface</a>
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</td>
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</tr>
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</table>
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<table>
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<tr>
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<td valign="top" width="22"><img height="20" width="20" src="favicon.ico"></td>
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<td>
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<a href="#nfsmount">NFS Mount Command</a>
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</td>
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</tr>
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</table>
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<table>
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<tr>
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<td valign="top" width="22"><img height="20" width="20" src="favicon.ico"></td>
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<td>
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<a href="#serverconfig">Configuring the NFS server (Ubuntu)</a>
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</td>
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</tr>
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</table>
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</td>
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</tr>
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</table></center>
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<table width ="100%">
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<tr bgcolor="#e4e4e4">
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<td>
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<a name="mountinterface"><h1>Mount Interface</h1></a>
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</td>
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</tr>
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</table>
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<p>
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A low-level, C-callable interface is provided to mount a file system.
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That interface is called <code>mount()</code> and is mentioned in the <a href="NuttxPortingGuide.html#NxFileSystem"><code>porting guide</code></a> and is prototyped in the header file <code>include/sys/mount.h</code>:
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</p>
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<ul><pre>
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int mount(const char *source, const char *target, const char *filesystemtype, unsigned long mountflags, const void *data);
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</pre></ul>
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<p>
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<b>Synopsis</b>:
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<code>mount()</code> attaches the filesystem specified by the <code>source</code> block device name into the root file system at the path specified by <code>target</code>.
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</p>
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<p>
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<b>Input Paramters</b>:
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<ul>
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<li><code>source</code>. A null-terminated string providing the fill path to a block driver in the NuttX psuedo-file system.
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<li><code>target</code>. The location in the NuttX psuedo-file system where the volume will be mounted.
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<li><code>filesystemtype</code>. A string identifying the type of file system to use.
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<li><code>mountflags</code>. Various flags that can be used to qualify how the file system is mounted.
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<li><code>data</code>. Opaque data that is passed to the file system with the mount occurs.
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</ul>
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</p>
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<p>
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<b>Returned Values</b>
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Zero is returned on success; -1 is returned on an error and <code>errno</code> is set appropriately:
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<ul>
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<li><code>EACCES</code>.
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A component of a path was not searchable or mounting a read-onlyfilesystem was attempted without giving the <code>MS_RDONLY</code> flag.
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</li>
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<li><code>EBUSY</code>.
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<code>source</code> is already mounted.
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</li>
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<li><code>EFAULT</code>.
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One of the pointer arguments points outside the user address space.
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</li>
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<li><code>EINVAL</code>.
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<code>source</code> had an invalid superblock.
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</li>
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<li><code>ENODEV</code>.
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<code>filesystemtype</code> not configured
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</li>
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<li><code>ENOENT</code>.
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A pathname was empty or had a nonexistent component.
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</li>
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<li><code>ENOMEM</code>.
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Could not allocate a memory to copy filenames or data into.
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</li>
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<li><code>ENOTBLK</code>.
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<code>source</code> is not a block device
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</li>
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</ul>
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</p>
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<p>
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This same interface can be used to mount a remote, NFS file system using some special parameters.
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The NFS mount differs from the <i>normal</i> file system mount in that: (1) there is no block driver for the NFS file system, and (2) special parameters must be passed as <code>data</code> to describe the remote NFS server.
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Thus the following code snippet might represent how an NFS file system is mounted:
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</p>
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<ul><pre>
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#include <sys/mount.h>
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#include <nuttx/fs/nfs.h>
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struct nfs_args data;
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char *mountpoint;
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ret = mount(NULL, mountpoint, string "nfs", 0, (FAR void *)&data);
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</pre></ul>
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<p>
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NOTE that: (1) the block driver paramter is <code>NULL</code>.
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The <code>mount()</code> is smart enough to know that no block driver is needed with the NFS file system.
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(2) The NFS file system is identified with the simple string "nfs"
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(3) A reference to <code>struct nfs_args</code> is passed as an NFS-specific argument.
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</p>
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<p>
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The NFS-specific interface is described in the file <code>include/nuttx/fs/nfs.h</code>.
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There you can see that <code>struct nfs_args</code> is defined as:
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</p>
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<ul><pre>
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struct nfs_args
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{
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uint8_t addrlen; /* Length of address */
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uint8_t sotype; /* Socket type */
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uint8_t flags; /* Flags, determines if following are valid: */
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uint8_t timeo; /* Time value in deciseconds (with NFSMNT_TIMEO) */
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uint8_t retrans; /* Times to retry send (with NFSMNT_RETRANS) */
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uint16_t wsize; /* Write size in bytes (with NFSMNT_WSIZE) */
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uint16_t rsize; /* Read size in bytes (with NFSMNT_RSIZE) */
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uint16_t readdirsize; /* readdir size in bytes (with NFSMNT_READDIRSIZE) */
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char *path; /* Server's path of the directory being mount */
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struct sockaddr_storage addr; /* File server address (requires 32-bit alignment) */
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};
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</pre></ul>
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<table width ="100%">
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<tr bgcolor="#e4e4e4">
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<td>
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<a name="nfsmount"><h1>NFS Mount Command</h1></a>
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</td>
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</tr>
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</table>
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<p>
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The <a href="NuttShell.html">NuttShell (NSH)</a> also supports a command called <code>nfsmount</code>
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that can be used to mount a remote file system via the NSH command line.
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</p>
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<p>
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<b>Command Syntax:</b>
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</p>
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<ul><pre>
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nfsmount <server-address> <mount-point> <remote-path>
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</pre></ul>
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<p>
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<b>Synopsis</b>.
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The <code>nfsmount</code> command mounts a network file system in the NuttX psuedo filesystem.
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The <code>nfsmount</code> will use NFSv3 UDP protocol to mount the remote file system.
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</p>
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<p>
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<b>Command Line Arguments</b>.
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The <code>nfsmount</code> takes three arguments:
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</p>
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<ol>
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<li>
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The <code><server-address></code> is the IP address of the server exporting the file system you wish to mount.
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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.
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</li>
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<li>
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The <code><mount-point ></code> is the location in the NuttX pseudo filesystem where the mounted volume will appear.
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This mount point can only reside in the NuttX pseudo filesystem.
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By convention, this mount point is a subdirectory under <code>/mnt</code>.
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The mount command will create whatever psuedo directories that may be needed to complete the full path (but the full path must not already exist).
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</li>
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<li>
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The <code><remote-path></code> is the file system <code>/</code> directory being exported from server.
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This <code>/</code> directory must have been configured for exportation on the server before when the NFS server was set up.
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</li>
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</ol>
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<p>
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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.
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</p>
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<p>
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<b>Example</b>.
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Suppose the the NFS server has been configured to export the directory <code>/export/shared</code>.
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The the following command would mount that file system (assuming that the target also has privileges to mount the file system).
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</p>
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<ul><pre>
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NuttShell (NSH)
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nsh> ls /mnt
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/mnt:
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nsh: ls: no such directory: /mnt
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nsh> nfsmount 10.0.0.1 /mnt/nfs /export/shared
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nsh> ls -l /mnt/nfs
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/mnt/nfs:
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drwxrwxrwx 4096 ..
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drwxrwxrwx 4096 testdir/
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-rw-rw-rw- 6 ctest.txt
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-rw-r--r-- 15 btest.txt
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drwxrwxrwx 4096 .
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nsh> echo "This is a test" >/mnt/nfs/testdir/testfile.txt
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nsh> ls -l /mnt/nfs/testdir
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/mnt/nfs/testdir:
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-rw-rw-rw- 21 another.txt
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drwxrwxrwx 4096 ..
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drwxrwxrwx 4096 .
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-rw-rw-rw- 16 testfile.txt
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nsh> cat /mnt/nfs/testdir/testfile.txt
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This is a test
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</pre></ul>
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<table width ="100%">
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<tr bgcolor="#e4e4e4">
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<td>
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<a name="serverconfig"><h1>Configuring the NFS server (Ubuntu)</h1></a>
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</td>
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</tr>
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</table>
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<p>
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Setting up the server will be done in two steps:
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First, setting up the configuration file for NFS, and then starting the NFS services.
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But first, you need to install the nfs server on Ubuntu with the these two commands:
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</p>
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<ul><pre>
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# sudo apt-get install nfs-common</FONT>
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# sudo apt-get install nfs-kernel-server</FONT>
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</pre></ul>
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<p>
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After that, we need to make or choose the directory we want to export from the NFS server.
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In our case, we are going to make a new directory called <code>/export</code>.
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</p>
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<ul><pre>
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# sudo mkdir /export
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</pre></ul>
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<p>
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It is important that <code>/export</code> directory allow access to everyone (777 permissions) as we will be accessing the NFS share from the client with no authentication.
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</p>
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<ul><pre>
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# sudo chmod 777 /export
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</pre></ul>
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<p>
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When all this is done, we will need to edit the configuration file to set up an NFS server: <code>/etc/exports</code>.
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This file contains a list of entries;
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each entry indicates a volume that is shared and how it is shared.
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For more information for a complete description of all the setup options for this file you can check in the man pages (<code>man export</code>).</p>
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An entry in <code>/etc/exports</code> will typically look like this:
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</p>
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<ul><pre>
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directory machine1(option11,option12)
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</pre></ul>
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<p>
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So for our example we export <coce>/export</code> to the client 10.0.0.2 add the entry:
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</p>
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<ul><pre>
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/export 10.0.0.2(rw)
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</pre></ul>
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<p>
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In our case we are using all the default options except for the <code>ro</code> that we replaced with <code>rw</code> so that our client will have read and write access to the directory that we are exporting.
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</p>
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</p>
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After we do all the require configurations, we are ready to start the server with the next command:
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</p>
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<ul><pre>
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# sudo /etc/init.d/nfs-kernel-server start
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</pre></ul>
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</p>
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Note: If you later decide to add more NFS exports to the /etc/exports file, you will need to either restart NFS daemon
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or run command exportfs.
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</p>
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<ul><pre>
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# sudo /etc/init.d/nfs-kernel-server start
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</pre></ul>
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<p>Or</p>
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<ul><pre>
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# exportfs -ra
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</pre></ul>
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<p>
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Now we can check if the export directory and our mount point is properly set up.
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</p>
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<ul><pre>
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# sudo showmount -e
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# sudo showmount -a
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</pre></ul>
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<p>
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And also we can verify if NFS is running in the system with:
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</p>
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<P STYLE="margin-left: 0.49in; margin-bottom: 0in; line-height: 100%">
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<ul><pre>
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# rpcinfo –p</FONT>
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program vers proto port
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100000 2 tcp 111 portmapper
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100000 2 udp 111 portmapper
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100011 1 udp 749 rquotad
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100011 2 udp 749 rquotad
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100005 1 udp 759 mountd
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100005 1 tcp 761 mountd
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100005 2 udp 764 mountd
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100005 2 tcp 766 mountd
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100005 3 udp 769 mountd
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100005 3 tcp 771 mountd
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100003 2 udp 2049 nfs
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100003 3 udp 2049 nfs
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300019 1 tcp 830 amd
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300019 1 udp 831 amd
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100024 1 udp 944 status
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100024 1 tcp 946 status
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100021 1 udp 1042 nlockmgr
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100021 3 udp 1042 nlockmgr
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100021 4 udp 1042 nlockmgr
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100021 1 tcp 1629 nlockmgr
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100021 3 tcp 1629 nlockmgr
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100021 4 tcp 1629 nlockmgr
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</pre></ul>
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<p>
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Now your NFS sever is sharing <code>/export</code> directory to be accessed.
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</p>
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</body>
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</html>
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@ -35,6 +35,7 @@
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<li><a href="NuttXNxFlat.html" target="main">NXFLAT</a></li>
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<li><a href="NXGraphicsSubsystem.html" target="main">NX Graphics</a></li>
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<li><a href="NxWidgets.html" target="main">NxWidgets</a></li>
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<li><a href="NfsHowTo.html" target="main">NFS How-To</a></li>
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<li><a href="NuttXDemandPaging.html" target="main">Demand Paging</a></li>
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<li><a href="UsbTrace.html" target="main">USB Trace</a></li>
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<li><a href="README.html" target="main">README Files</a></li>
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