contrib/intro/libguestfs-intro.html


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<html>
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    <title>Short introduction to libguestfs</title>
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  <body>
    <h1>Short introduction to libguestfs</h1>
    <author>by Richard W.M. Jones &lt;rjones@redhat.com&gt;</author>

    <h2>The Idea</h2>

    <p><b>Reuse qemu, Linux kernel and userspace tools</b> to read and
    write disk images.</p>

    <img src="overview.svg"/>

    <h2>The Stable API</h2>

<pre>
  /* get the Linux VFS type corresponding to a mounted device */
extern char *<b>guestfs_vfs_type</b> (guestfs_h *g, const char *device);
</pre>

<table style="margin-bottom: 4em;" width="100%">
  <tr><td valign="top">Example using this API:</td><td>
<pre>
#include &lt;guestfs.h&gt;

char *fstype = <b>guestfs_vfs_type (g, "/dev/vda1")</b>;
printf ("%s\n", fstype);
free (fstype);
&rarr; <b>ntfs</b>
</pre>
<p class="sourcelnk"><a href="http://git.annexia.org/?p=libguestfs.git;a=blob;f=fish/inspect.c;h=2ca54d2296fce5370504c1085cbcd7ac1b51ad3a;hb=HEAD#l208">click&nbsp;to&nbsp;see&nbsp;a&nbsp;real&nbsp;example&nbsp;...</a></p>
    </td>
  </tr>
</table>

    <table width="100%">
      <tr><td valign="top">

<pre style="font-size: 80%;">
  ("<b>vfs_type</b>",
   (RString "fstype",
        [Device "device"], []),
   198, [],
   [ (* tests *) ],
   "get the Linux VFS type corresponding to a mounted device",
   "\
This command gets the filesystem type corresponding to
the filesystem on C&lt;device&gt;.

For most filesystems, the result is the name of the Linux
VFS module which would be used to mount this filesystem
if you mounted it without specifying the filesystem type.
For example a string such as C&lt;ext3&gt; or C&lt;ntfs&gt;.");
</pre>
<p class="sourcelnk"><a href="http://git.annexia.org/?p=libguestfs.git;a=blob;f=generator/generator_actions.ml;h=d3fa3e0b939eb047a5ff103a68f09c6898807748;hb=HEAD#l4775">full&nbsp;source&nbsp;...</a></p>

        </td>
        <td valign="top">

<pre style="font-size: 80%;">
char *
<b>do_vfs_type</b> (const char *device)
{
  return get_blkid_tag (device, "TYPE");
}

static char *
get_blkid_tag (const char *device, const char *tag)
{
  char *out, *err;
  int r;

  r = commandr (&amp;out, &amp;err,
                "blkid",
                "-c", "/dev/null",
                "-o", "value", "-s", tag, device, NULL);
  if (r != 0 &amp;&amp; r != 2) {
    if (r &gt;= 0)
      reply_with_error ("%s: %s (blkid returned %d)",
                        device, err, r);
    else
      reply_with_error ("%s: %s", device, err);
    free (out);
    free (err);
    return NULL;
  }

  /* ... */

  return out;             /* caller frees */
}
</pre>
<p class="sourcelnk"><a href="http://git.annexia.org/?p=libguestfs.git;a=blob;f=daemon/blkid.c;hb=HEAD">full&nbsp;source&nbsp;...</a></p>

        </td>
      </tr>
    </table>

    <p>
      Just these two fragments generate:
    </p>

    <ul>
      <li> bindings in <a href="http://libguestfs.org/guestfs.3.html#api_overview">C</a>,
        <a href="http://libguestfs.org/guestfs-perl.3.html">Perl</a>,
        <a href="http://libguestfs.org/guestfs-python.3.html">Python</a>,
        <a href="http://libguestfs.org/guestfs-ruby.3.html">Ruby</a>,
        <a href="http://libguestfs.org/guestfs-java.3.html">Java</a>,
        <a href="http://libguestfs.org/guestfs-ocaml.3.html">OCaml</a>,
        PHP,
        Haskell,
        <a href="http://libguestfs.org/guestfs-erlang.3.html">Erlang</a>
        and C# </li>
      <li> <a href="http://libguestfs.org/guestfish.1.html">guestfish</a>
        (shell script) </li>
      <li> documentation in man pages and HTML </li>
      <li> internal RPC code </li>
    </ul>

    <h2>Tools written around the API</h2>

    <img src="tools.svg" />

    <table>
      <tr><td valign="top">
<pre>
<b>guestfish -N fs -m /dev/sda1 &lt;&lt;EOF</b>
  <font style="color: green;">mkdir /etc
  upload /etc/resolv.conf /etc/resolv.conf
  write /etc/hostname "test01.redhat.com"</font>
<b>EOF</b>
</pre>
<p class="sourcelnk"><a href="http://libguestfs.org/guestfish.1.html">manual&nbsp;...</a></p>
        </td><td valign="top">
<pre>
<b>virt-df -a /dev/vg/F15x32 -h</b>
Filesystem                    Size  Used Available Use%
F15x32:/dev/sda1              484M   31M      428M   7%
F15x32:/dev/vg_f15x32/lv_root 5.5G  3.4G      1.8G  63%
</pre>
<p class="sourcelnk"><a href="http://libguestfs.org/virt-df.1.html">manual&nbsp;...</a></p>
      </td></tr>
      <tr><td valign="top">
<pre>
<b>virt-edit -c qemu:///system -d F15x32 /etc/passwd</b>
<i>(launches editor)</i>
</pre>
<p class="sourcelnk"><a href="http://libguestfs.org/virt-edit.1.html">manual&nbsp;...</a></p>
        </td><td valign="top">
<pre>
<b>virt-win-reg -c qemu:///system --unsafe-printable-strings \
  Win7x32 'HKLM\SYSTEM\ControlSet001\Services\Tcpip\Parameters' \
  | grep DhcpIPAddress</b>
"DhcpIPAddress"=str(1):"192.168.122.178"
</pre>
<p class="sourcelnk"><a href="http://libguestfs.org/virt-win-reg.1.html">manual&nbsp;...</a></p>
      </td></tr>
    </table>

    <h2>Inspection</h2>


    <h2>V2V &amp; P2V</h2>


    <h2>Read more ...</h2>

    <p>
      <a href="http://libguestfs.org/">libguestfs.org</a> is the
      main website.
    </p>

    <p>
      <a href="http://libguestfs.org/guestfs.3.html">guestfs(3)</a>
      is the manual page documenting the C API and the internals.
    </p>

    <p>
      There are manual pages
      documenting <a href="http://libguestfs.org/guestfish.1.html">guestfish</a>, <a href="http://libguestfs.org/guestmount.1.html">guestmount</a>
      and each virt tool.  See
      the <a href="http://libguestfs.org/">main website</a> or your
      local man command.
    </p>

    <hr/>

    <p style="font-size: 70%;">
      This page &copy; 2011 Red Hat Inc. and distributed
      under the terms of the GNU General Public License as published by
      the Free Software Foundation; either version 2 of the License, or
      (at your option) any later version.
    </p>

  </body>
</html>