A low-level, C-callable interface is provided to mount a file system.
That interface is called <code>mount()</code> and is mentioned in the <ahref="NuttxPortingGuide.html#NxFileSystem"><code>porting guide</code></a> and is prototyped in the header file <code>include/sys/mount.h</code>:
</p>
<ul><pre>
int mount(const char *source, const char *target, const char *filesystemtype, unsigned long mountflags, const void *data);
</pre></ul>
<p>
<b>Synopsis</b>:
<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>.
</p>
<p>
<b>Input Paramters</b>:
<ul>
<li><code>source</code>. A null-terminated string providing the fill path to a block driver in the NuttX pseudo-file system.
<li><code>target</code>. The location in the NuttX pseudo-file system where the volume will be mounted.
<li><code>filesystemtype</code>. A string identifying the type of file system to use.
<li><code>mountflags</code>. Various flags that can be used to qualify how the file system is mounted.
<li><code>data</code>. Opaque data that is passed to the file system with the mount occurs.
</ul>
</p>
<p>
<b>Returned Values</b>
Zero is returned on success; -1 is returned on an error and <code>errno</code> is set appropriately:
<ul>
<li><code>EACCES</code>.
A component of a path was not searchable or mounting a read-onlyfilesystem was attempted without giving the <code>MS_RDONLY</code> flag.
</li>
<li><code>EBUSY</code>.
<code>source</code> is already mounted.
</li>
<li><code>EFAULT</code>.
One of the pointer arguments points outside the user address space.
</li>
<li><code>EINVAL</code>.
<code>source</code> had an invalid superblock.
</li>
<li><code>ENODEV</code>.
<code>filesystemtype</code> not configured
</li>
<li><code>ENOENT</code>.
A pathname was empty or had a nonexistent component.
</li>
<li><code>ENOMEM</code>.
Could not allocate a memory to copy filenames or data into.
</li>
<li><code>ENOTBLK</code>.
<code>source</code> is not a block device
</li>
</ul>
</p>
<p>
This same interface can be used to mount a remote, NFS file system using some special parameters.
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.
Thus the following code snippet might represent how an NFS file system is mounted:
</p>
<ul><pre>
#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);
</pre></ul>
<p>
NOTE that: (1) the block driver paramter is <code>NULL</code>.
The <code>mount()</code> 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 <code>struct nfs_args</code> is passed as an NFS-specific argument.
</p>
<p>
The NFS-specific interface is described in the file <code>include/nuttx/fs/nfs.h</code>.
There you can see that <code>struct nfs_args</code> is defined as:
</p>
<ul><pre>
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 */
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.
When all this is done, we will need to edit the configuration file to set up an NFS server: <code>/etc/exports</code>.
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 (<code>man export</code>).</p>
An entry in <code>/etc/exports</code> will typically look like this:
</p>
<ul><pre>
directory machine1(option11,option12)
</pre></ul>
<p>
So for our example we export <coce>/export</code> to the client 10.0.0.2 add the entry:
</p>
<ul><pre>
/export 10.0.0.2(rw)
</pre></ul>
<p>
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.
