259 lines
12 KiB
HTML
259 lines
12 KiB
HTML
|
|
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">
|
|
<html>
|
|
<head>
|
|
<title>Fedora Project, sponsored by Red Hat</title>
|
|
<base href="http://fedora.redhat.com/">
|
|
<meta http-equiv="Content-Type" content="text/html">
|
|
<link rel="stylesheet" type="text/css" media="print" href="/css/print.css">
|
|
<style type="text/css" media="screen">
|
|
@import url("/css/layout.css");
|
|
@import url("/css/content.css");
|
|
@import url("/css/docbook.css");
|
|
</style>
|
|
<meta name="MSSmartTagsPreventParsing" content="TRUE">
|
|
<link rel="shortcut icon" href="/images/favicon.ico">
|
|
<link rel="icon" href="/images/favicon.ico">
|
|
</head>
|
|
|
|
<body>
|
|
<!-- header BEGIN -->
|
|
<div id="fedora-header">
|
|
<div id="fedora-header-logo">
|
|
<a href="/"><img src="/images/header-fedora_logo.png" alt="Fedora Project"></a>
|
|
</div>
|
|
|
|
<div id="fedora-header-items">
|
|
<span class="fedora-header-icon">
|
|
<a href="/download/"><img src="/images/header-download.png" alt=" ">Download</a>
|
|
<a href="/projects/"><img src="/images/header-projects.png" alt=" ">Projects</a>
|
|
<a href="/about/faq/"><img src="/images/header-faq.png" alt=" ">FAQ</a></span>
|
|
</div>
|
|
</div>
|
|
|
|
<div id="fedora-nav"></div>
|
|
<!-- header END -->
|
|
|
|
<!-- leftside BEGIN -->
|
|
<div id="fedora-side-left">
|
|
<div id="fedora-side-nav-label">Site Navigation:</div> <ul id="fedora-side-nav">
|
|
<li><a href="/">Home</a></li>
|
|
<li><a href="/download/">Download</a></li>
|
|
<li><a href="/docs/">Docs</a></li>
|
|
<li><a href="/projects/">Projects</a></li>
|
|
<li><a href="/participate/">Participate</a></li>
|
|
<li><a href="/about/">About</a></li>
|
|
</ul>
|
|
</div>
|
|
|
|
<!-- leftside END -->
|
|
|
|
<!-- content BEGIN -->
|
|
<div id="fedora-middle-two">
|
|
<div class="fedora-corner-tr"> </div>
|
|
<div class="fedora-corner-tl"> </div>
|
|
<div id="fedora-content">
|
|
<!-- content BEGIN -->
|
|
<h1>Udev on Fedora</h1>
|
|
<h2>by Harald Hoyer</h2>
|
|
<p>
|
|
This document tries to reveal the secrets of udev and how it works on Fedora.
|
|
</p>
|
|
<p>
|
|
udev was developed by Greg Kroah-Hartman <greg@kroah.com> with much
|
|
help from Dan Stekloff <dsteklof@us.ibm.com>, Kay Sievers <kay.sievers@vrfy.org>,
|
|
and many others.
|
|
</p>
|
|
<p>
|
|
The <a href="http://www.kernel.org/pub/linux/utils/kernel/hotplug/udev.html">udev homepage</a> and the
|
|
Linux-hotplug-devel mailing list <a href="https://lists.sourceforge.net/lists/listinfo/linux-hotplug-devel">https://lists.sourceforge.net/lists/listinfo/linux-hotplug-devel</a> are the main development sources.
|
|
</p><p>
|
|
</p>
|
|
|
|
<h2>What Does Udev Do?</h2>
|
|
<p>
|
|
udev provides a dynamic device directory containing only the files for
|
|
actually present devices. It creates or removes device node files usually
|
|
located in the <tt class="filename">/dev/</tt> directory, or it renames network interfaces.
|
|
</p><p>
|
|
As part of the hotplug subsystem, udev is executed if a kernel device
|
|
is added or removed from the system. On device creation, udev reads
|
|
the sysfs directory of the given device to collect device attributes
|
|
like label, serial number or bus device number. These attributes may
|
|
be used as keys to determine a unique name for the device. udev maintains
|
|
a database for devices present on the system.
|
|
On device removal, udev queries its database for the name of the device
|
|
file to be deleted.
|
|
</p><p>
|
|
udev gets called by hotplug, if a module is loaded, and a device is added
|
|
or removed. udev looks in <tt class="filename">/sys/</tt>, if the driver provides a "dev" file, which
|
|
contains the major and minor number for a device node to communicate with
|
|
the driver. After looking in the udev rules (in the <tt class="filename">/etc/udev/rules.d/</tt> directory), which
|
|
specify the device node filename and symlinks, a device node is created
|
|
in <tt class="filename">/dev/</tt> with the permissions, which are specified in <tt class="filename">/etc/udev/permissions.d/</tt>.
|
|
</p>
|
|
After device node creation, removal, or network device renaming, udev
|
|
executes the programs in the directory tree under <tt class="filename">/etc/dev.d/</tt>. The
|
|
name of a program must end with the <tt class="filename">.dev</tt> suffix, to be recognized.
|
|
In addition to the hotplug environment variables, DEVNAME is exported
|
|
to make the name of the created node or the name the network device is
|
|
renamed to, available to the executed program. The programs in every
|
|
directory are sorted in lexical order, while the directories are
|
|
searched in the following order:
|
|
<ul>
|
|
<li><tt class="filename">/etc/dev.d/$(DEVNAME)/*.dev</tt></li>
|
|
<li><tt class="filename">/etc/dev.d/$(SUBSYSTEM)/*.dev</tt></li>
|
|
<li><tt class="filename">/etc/dev.d/default/*.dev</tt></li>
|
|
</ul>
|
|
|
|
<h2>How is Udev Integrated on Fedora?</h2>
|
|
<h3><tt class="command">initrd</tt> / <tt class="command">initfs</tt></h3>
|
|
<p>
|
|
<tt class="command">mkinitrd</tt> copies <tt class="filename">/sbin/udev.static</tt>
|
|
to the <tt class="command">initrd</tt> <tt class="filename">/sbin/udev</tt> and symlinks it to
|
|
<tt class="filename">/sbin/udevstart</tt>.
|
|
</p><p>
|
|
After the kernel boots, it executes the nash script of the <tt class="command">initrd</tt>. This
|
|
mounts a tmpfs filesystem on <tt class="filename">/dev/</tt>. Instead of hotplug <tt class="command">/sbin/udev</tt> is
|
|
called in the <tt class="command">initrd</tt> phase. udevstart creates all device nodes for the
|
|
devices, which are compiled in the kernel and for the modules, which
|
|
are loaded by nash. </p>
|
|
|
|
<h4>Problems</h4>
|
|
|
|
The whole udev and hotplug infrastructure is
|
|
not available in <tt class="command">initrd</tt>. Thus no hotplug scripts, udev rules, and
|
|
permissions and no <tt class="filename">/etc/dev.d/</tt> scripts are executed for any hotplug
|
|
event, which is sent from the kernel.
|
|
|
|
<h3><tt class="filename">rc.sysinit</tt></h3>
|
|
<p> First, if SELinux is loaded and enabled,
|
|
the context of <tt class="filename">/dev/</tt> is set. <tt class="filename">rc.sysinit</tt> calls <tt class="filename">/sbin/start_udev</tt>.
|
|
<tt class="filename">start_udev</tt> mounts a tmpfs filesystem on <tt class="filename">/dev/</tt>, if there is none already
|
|
mounted. Then it creates some device nodes, which need module
|
|
autoloading, or where there is no kernel module. After that
|
|
<tt class="command">/sbin/udevstart</tt> is called again, which simulates the hotplug events in
|
|
the <tt class="command">initrd</tt> phase, to apply the whole udev rules and permissions. After
|
|
that <tt class="filename">rc.sysinit</tt> parses the ouput of <tt class="filename">/sbin/kmodule</tt> and loads every
|
|
module. This should provide device nodes for all hardware found on your
|
|
computer. </p>
|
|
<h3>Console User Permissions</h3>
|
|
<p>
|
|
<tt class="filename">/etc/dev.d/default/pam_console.dev</tt> is called whenever a device node is
|
|
created and calls <tt class="filename">/sbin/pam_console_setowner</tt> with the filename (and an
|
|
optional symlink) of the device node. This sets the permissions for
|
|
console users like specified in <tt class="filename">/etc/security/console.perms</tt>. </p>
|
|
<h2>Customizing Udev on Fedora</h2>
|
|
<p>
|
|
Read the manpage of udev and udevinfo.
|
|
Please try not to modify the files of RPM packages.
|
|
</p>
|
|
<h3>New Rules</h3>
|
|
<p>
|
|
New rules should be placed in a file, which ends in <tt class="filename">.rules</tt> in
|
|
<tt class="filename">/etc/udev/rules.d/</tt>. Please do not use <tt class="filename">50-udev.rules</tt>. The supported and
|
|
preferred way is to create rules without the "NAME" tag and only
|
|
create "SYMLINK"s. </p><p>
|
|
A nice document describing how to write rules can be found on <a href="http://www.reactivated.net/udevrules.php">http://www.reactivated.net/udevrules.php</a>.
|
|
</p>
|
|
|
|
<h3>Permissions</h3>
|
|
New permissions should be placed in a file, which ends in
|
|
<tt class="filename">.permissions</tt> in <tt class="filename">/etc/udev/permissions.d/</tt>. Please do not use
|
|
<tt class="filename">50-udev.permissions</tt>.
|
|
|
|
<h3>But I Really Want My Device Node!</h3>
|
|
<p>
|
|
Put them in <tt class="filename">/etc/udev/devices/</tt>, and they will get copied to <tt class="filename">/dev/</tt>. <a href="https://bugzilla.redhat.com/bugzilla">File a bugzilla entry</a>, if you think that should be done per default.
|
|
</p>
|
|
|
|
<h2>Updating to udev Without <tt class="filename">/dev/</tt></h2>
|
|
<p>
|
|
The steps to upgrade without Anaconda or a rescue CD are (NOT recommended):
|
|
</p>
|
|
|
|
<ul>
|
|
<li>start from a kernel-2.6
|
|
</li><li>Make sure <tt class="filename">/sys/</tt> is mounted
|
|
</li><li>Install the latest <tt class="filename">initscripts</tt> package
|
|
</li><li>Install the latest <tt class="filename">udev</tt> package
|
|
</li><li>Execute <tt class="command">/sbin/start_udev</tt>
|
|
</li><li>Install the latest <tt class="filename">mkinitrd</tt> package
|
|
</li><li>Install the latest <tt class="filename">kernel</tt> package
|
|
</li><li>Or execute <tt class="command">mkinitrd</tt> for your existing kernel(s)
|
|
</li></ul>
|
|
|
|
<h2>Udev without <tt class="command">initrd</tt></h2>
|
|
|
|
<p>Install Fedore Core as usual and reboot. Execute the following commands
|
|
</p>
|
|
|
|
<pre class="screen">
|
|
<tt class="command">
|
|
mkdir /tmp/dev
|
|
mount --move /dev /tmp/dev
|
|
sbin/MAKEDEV null console zero
|
|
mount --move /tmp/dev /dev
|
|
</tt></pre>
|
|
Install your kernel without an <tt class="command">initrd</tt>. Reboot.
|
|
<p>
|
|
You will get some SELinux errors, and syslogd will not work as expected.
|
|
</p>
|
|
<h2>Current Problems on Fedora</h2>
|
|
<p>
|
|
<a href="http://bugzilla.redhat.com/bugzilla/buglist.cgi?short_desc_type=allwordssubstr&component=udev&bug_status=ASSIGNED&bug_status=MODIFIED&bug_status=NEEDINFO&bug_status=NEW&bug_status=REOPENED&bug_status=VERIFIED&bug_severity=high&bug_severity=low&bug_severity=normal&bug_severity=security&bug_severity=translation&long_desc_type=allwordssubstr&bug_file_loc_type=allwordssubstr&status_whiteboard_type=allwordssubstr&fixed_in_type=allwordssubstr&devel_whiteboard_type=allwordssubstr&keywords_type=allwords&cust_facing=YES&emailassigned_to1=1&emailtype1=exact&emailreporter2=1&emailtype2=exact&bugidtype=include&chfieldto=Now&cmdtype=doit&remaction=run&namedcmd=blank&order=Reuse+same+sort+as+last+time&field0-0-0=noop&type0-0-0=noop">All open bugs for <code class="filename">udev</code></a>
|
|
</p>
|
|
<h3>Nvidia</h3>
|
|
<p>Quick solution: If you do not need rhgb, just load the nvidia module in <tt class="filename">/etc/rc.local</tt>
|
|
</p><p>
|
|
If you have udev >= 032-5, load the nvidia module:
|
|
</p>
|
|
<pre class="screen">
|
|
<tt class="command">
|
|
cp -a /dev/nvidia* /etc/udev/devices
|
|
chown root.root /etc/udev/devices/nvidia*
|
|
</tt></pre>
|
|
|
|
<p>The Bugzilla for this problem is <strike><a href="https://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=133900">133900</a></strike>.</p>
|
|
<h3>Palm Pilot</h3>
|
|
<p>
|
|
If you have udev >= 032-5, execute the command:
|
|
</p>
|
|
<pre class="screen">
|
|
<tt class="command">
|
|
ln -s ttyUSB1 /etc/udev/devices/pilot
|
|
</tt></pre>
|
|
|
|
<h3>ISDN</h3>
|
|
<p>
|
|
If you have udev >= 032-5:
|
|
</p>
|
|
<pre class="screen">
|
|
<tt class="command">
|
|
/sbin/MAKEDEV -d /etc/udev/devices isdn
|
|
</tt></pre>
|
|
</pre>
|
|
|
|
<!-- content END -->
|
|
|
|
|
|
</div>
|
|
<div class="fedora-corner-br"> </div>
|
|
<div class="fedora-corner-bl"> </div>
|
|
</div>
|
|
<!-- content END -->
|
|
|
|
<!-- footer BEGIN -->
|
|
<div id="fedora-footer">
|
|
Copyright © 2003-2004 Red Hat, Inc. All rights reserved.
|
|
<br>The Fedora Project is not a supported product of Red Hat, Inc.
|
|
<br><a href="/legal/">Legal</a> | <a href="/about/trademarks/">Trademark Guidelines</a>
|
|
<br>
|
|
This page last modified at: 2004/10/16 02:25:17
|
|
<br>
|
|
</div>
|
|
<!-- footer END -->
|
|
</body>
|
|
</html>
|
|
|