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diff --git a/man/udev.xml b/man/udev.xml new file mode 100644 index 0000000000..7ec7a3fed0 --- /dev/null +++ b/man/udev.xml @@ -0,0 +1,705 @@ +<?xml version='1.0'?> +<?xml-stylesheet type="text/xsl" href="http://docbook.sourceforge.net/release/xsl/current/xhtml/docbook.xsl"?> +<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN" + "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd"> + +<refentry id="udev"> + <refentryinfo> + <title>udev</title> + <productname>systemd</productname> + <authorgroup> + <author> + <contrib>Developer</contrib> + <firstname>Greg</firstname> + <surname>Kroah-Hartmann</surname> + <email>greg@kroah.com</email> + </author> + <author> + <contrib>Developer</contrib> + <firstname>Kay</firstname> + <surname>Sievers</surname> + <email>kay@vrfy.org</email> + </author> + </authorgroup> + </refentryinfo> + + <refmeta> + <refentrytitle>udev</refentrytitle> + <manvolnum>7</manvolnum> + </refmeta> + + <refnamediv> + <refname>udev</refname> + <refpurpose>Linux dynamic device management</refpurpose> + </refnamediv> + + <refsect1><title>Description</title> + <para>udev supplies the system software with device events, manages permissions + of device nodes and may create additional symlinks in the <filename>/dev</filename> + directory, or renames network interfaces. The kernel usually just assigns unpredictable + device names based on the order of discovery. Meaningful symlinks or network device + names provide a way to reliably identify devices based on their properties or + current configuration.</para> + + <para>The udev daemon, <citerefentry><refentrytitle>systemd-udevd.service</refentrytitle> + <manvolnum>8</manvolnum></citerefentry>, receives device uevents directly from + the kernel whenever a device is added or removed from the system, or it changes its + state. When udev receives a device event, it matches its configured set of rules + against various device attributes to identify the device. Rules that match may + provide additional device information to be stored in the udev database or + to be used to create meaningful symlink names.</para> + + <para>All device information udev processes is stored in the udev database and + sent out to possible event subscribers. Access to all stored data and the event + sources is provided by the library libudev.</para> + </refsect1> + + <refsect1><title>Configuration</title> + <para>udev configuration files are placed in <filename>/etc/udev</filename> + and <filename>/usr/lib/udev</filename>. All empty lines or lines beginning with + '#' are ignored.</para> + + <refsect2><title>Configuration file</title> + <para>udev expects its main configuration file at <filename>/etc/udev/udev.conf</filename>. + It consists of a set of variables allowing the user to override default udev values. + The following variables can be set:</para> + <variablelist> + <varlistentry> + <term><option>udev_log</option></term> + <listitem> + <para>The logging priority. Valid values are the numerical syslog priorities + or their textual representations: <option>err</option>, <option>info</option> + and <option>debug</option>.</para> + </listitem> + </varlistentry> + </variablelist> + </refsect2> + + <refsect2><title>Rules files</title> + <para>The udev rules are read from the files located in the + system rules directory <filename>/usr/lib/udev/rules.d</filename>, + the volatile runtime directory <filename>/run/udev/rules.d</filename> + and the local administration directory <filename>/etc/udev/rules.d</filename>. + All rules files are collectively sorted and processed in lexical order, + regardless of the directories in which they live. However, files with + identical file names replace each other. Files in <filename>/etc</filename> + have the highest priority, files in <filename>/run</filename> take precedence + over files with the same name in <filename>/lib</filename>. This can be + used to override a system-supplied rules file with a local file if needed; + a symlink in <filename>/etc</filename> with the same name as a rules file in + <filename>/lib</filename>, pointing to <filename>/dev/null</filename>, + disables the rules file entirely.</para> + + <para>Rule files must have the extension <filename>.rules</filename>; other + extensions are ignored.</para> + + <para>Every line in the rules file contains at least one key-value pair. + There are two kinds of keys: match and assignment. + If all match keys are matching against its value, the rule gets applied and the + assignment keys get the specified value assigned.</para> + + <para>A matching rule may rename a network interface, add symlinks + pointing to the device node, or run a specified program as part of + the event handling.</para> + + <para>A rule consists of a comma-separated list of one or more key-value pairs. + Each key has a distinct operation, depending on the used operator. Valid + operators are:</para> + <variablelist> + <varlistentry> + <term><option>==</option></term> + <listitem> + <para>Compare for equality.</para> + </listitem> + </varlistentry> + + <varlistentry> + <term><option>!=</option></term> + <listitem> + <para>Compare for inequality.</para> + </listitem> + </varlistentry> + + <varlistentry> + <term><option>=</option></term> + <listitem> + <para>Assign a value to a key. Keys that represent a list are reset + and only this single value is assigned.</para> + </listitem> + </varlistentry> + + <varlistentry> + <term><option>+=</option></term> + <listitem> + <para>Add the value to a key that holds a list of entries.</para> + </listitem> + </varlistentry> + + <varlistentry> + <term><option>:=</option></term> + <listitem> + <para>Assign a value to a key finally; disallow any later changes.</para> + </listitem> + </varlistentry> + </variablelist> + + <para>The following key names can be used to match against device properties. + Some of the keys also match against properties of the parent devices in sysfs, + not only the device that has generated the event. If multiple keys that match + a parent device are specified in a single rule, all these keys must match at + one and the same parent device.</para> + <variablelist> + <varlistentry> + <term><option>ACTION</option></term> + <listitem> + <para>Match the name of the event action.</para> + </listitem> + </varlistentry> + + <varlistentry> + <term><option>DEVPATH</option></term> + <listitem> + <para>Match the devpath of the event device.</para> + </listitem> + </varlistentry> + + <varlistentry> + <term><option>KERNEL</option></term> + <listitem> + <para>Match the name of the event device.</para> + </listitem> + </varlistentry> + + <varlistentry> + <term><option>NAME</option></term> + <listitem> + <para>Match the name of a network interface. It can be used once the + NAME key has been set in one of the preceding rules.</para> + </listitem> + </varlistentry> + + <varlistentry> + <term><option>SYMLINK</option></term> + <listitem> + <para>Match the name of a symlink targeting the node. It can + be used once a SYMLINK key has been set in one of the preceding + rules. There may be multiple symlinks; only one needs to match. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><option>SUBSYSTEM</option></term> + <listitem> + <para>Match the subsystem of the event device.</para> + </listitem> + </varlistentry> + <varlistentry> + <term><option>DRIVER</option></term> + <listitem> + <para>Match the driver name of the event device. Only set this key for devices + which are bound to a driver at the time the event is generated.</para> + </listitem> + </varlistentry> + <varlistentry> + <term><option>ATTR{<replaceable>filename</replaceable>}</option></term> + <listitem> + <para>Match sysfs attribute values of the event device. Trailing + whitespace in the attribute values is ignored unless the specified match + value itself contains trailing whitespace. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><option>KERNELS</option></term> + <listitem> + <para>Search the devpath upwards for a matching device name.</para> + </listitem> + </varlistentry> + + <varlistentry> + <term><option>SUBSYSTEMS</option></term> + <listitem> + <para>Search the devpath upwards for a matching device subsystem name.</para> + </listitem> + </varlistentry> + + <varlistentry> + <term><option>DRIVERS</option></term> + <listitem> + <para>Search the devpath upwards for a matching device driver name.</para> + </listitem> + </varlistentry> + + <varlistentry> + <term><option>ATTRS{<replaceable>filename</replaceable>}</option></term> + <listitem> + <para>Search the devpath upwards for a device with matching sysfs attribute values. + If multiple <option>ATTRS</option> matches are specified, all of them + must match on the same device. Trailing whitespace in the attribute values is ignored + unless the specified match value itself contains trailing whitespace.</para> + </listitem> + </varlistentry> + + <varlistentry> + <term><option>TAGS</option></term> + <listitem> + <para>Search the devpath upwards for a device with matching tag.</para> + </listitem> + </varlistentry> + + <varlistentry> + <term><option>ENV{<replaceable>key</replaceable>}</option></term> + <listitem> + <para>Match against a device property value.</para> + </listitem> + </varlistentry> + + <varlistentry> + <term><option>TAG</option></term> + <listitem> + <para>Match against a device tag.</para> + </listitem> + </varlistentry> + + <varlistentry> + <term><option>TEST{<replaceable>octal mode mask</replaceable>}</option></term> + <listitem> + <para>Test the existence of a file. An octal mode mask can be specified + if needed.</para> + </listitem> + </varlistentry> + + <varlistentry> + <term><option>PROGRAM</option></term> + <listitem> + <para>Execute a program to determine whether there + is a match; the key is true if the program returns + successfully. The device properties are made available to the + executed program in the environment. The program's stdout + is available in the RESULT key.</para> + <para>This can only be used for very short-running foreground tasks. For details + see <option>RUN</option>.</para> + </listitem> + </varlistentry> + + <varlistentry> + <term><option>RESULT</option></term> + <listitem> + <para>Match the returned string of the last PROGRAM call. This key can + be used in the same or in any later rule after a PROGRAM call.</para> + </listitem> + </varlistentry> + </variablelist> + + <para>Most of the fields support shell-style pattern matching. The following + pattern characters are supported:</para> + <variablelist> + <varlistentry> + <term><option>*</option></term> + <listitem> + <para>Matches zero or more characters.</para> + </listitem> + </varlistentry> + <varlistentry> + <term><option>?</option></term> + <listitem> + <para>Matches any single character.</para> + </listitem> + </varlistentry> + <varlistentry> + <term><option>[]</option></term> + <listitem> + <para>Matches any single character specified within the brackets. For + example, the pattern string 'tty[SR]' would match either 'ttyS' or 'ttyR'. + Ranges are also supported via the '-' character. + For example, to match on the range of all digits, the pattern [0-9] could + be used. If the first character following the '[' is a '!', any characters + not enclosed are matched.</para> + </listitem> + </varlistentry> + </variablelist> + + <para>The following keys can get values assigned:</para> + <variablelist> + <varlistentry> + <term><option>NAME</option></term> + <listitem> + <para>The name to use for a network interface. The name of a device node + cannot be changed by udev, only additional symlinks can be created.</para> + </listitem> + </varlistentry> + + <varlistentry> + <term><option>SYMLINK</option></term> + <listitem> + <para>The name of a symlink targeting the node. Every matching rule adds + this value to the list of symlinks to be created.</para> + <para>The set of characters to name a symlink is limited. Allowed + characters are [0-9A-Za-z#+-.:=@_/], valid utf8 character sequences, + and "\x00" hex encoding. All other characters are replaced by + a '_' character.</para> + <para>Multiple symlinks may be specified by separating the names by the + space character. In case multiple devices claim the same name, the link + always points to the device with the highest link_priority. If the current + device goes away, the links are re-evaluated and the device with the + next highest link_priority becomes the owner of the link. If no + link_priority is specified, the order of the devices (and which one of + them owns the link) is undefined.</para> + <para>Symlink names must never conflict with the kernel's default device + node names, as that would result in unpredictable behavior. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><option>OWNER, GROUP, MODE</option></term> + <listitem> + <para>The permissions for the device node. Every specified value overrides + the compiled-in default value.</para> + </listitem> + </varlistentry> + + <varlistentry> + <term><option>ATTR{<replaceable>key</replaceable>}</option></term> + <listitem> + <para>The value that should be written to a sysfs attribute of the + event device.</para> + </listitem> + </varlistentry> + + <varlistentry> + <term><option>ENV{<replaceable>key</replaceable>}</option></term> + <listitem> + <para>Set a device property value. Property names with a leading '.' + are neither stored in the database nor exported to events or + external tools (run by, say, the PROGRAM match key).</para> + </listitem> + </varlistentry> + + <varlistentry> + <term><option>TAG</option></term> + <listitem> + <para>Attach a tag to a device. This is used to filter events for users + of libudev's monitor functionality, or to enumerate a group of tagged + devices. The implementation can only work efficiently if only a few + tags are attached to a device. It is only meant to be used in + contexts with specific device filter requirements, and not as a + general-purpose flag. Excessive use might result in inefficient event + handling.</para> + </listitem> + </varlistentry> + + <varlistentry> + <term><option>RUN</option></term> + <listitem> + <para>Add a program to the list of programs to be executed for a specific + device.</para> + <para>If no absolute path is given, the program is expected to live in + /usr/lib/udev, otherwise the absolute path must be specified. The program + name and following arguments are separated by spaces. Single quotes can + be used to specify arguments with spaces.</para> + <para>This can only be used for very short-running foreground tasks. Running an + event process for a long period of time may block all further events for + this or a dependent device.</para> + <para>Starting daemons or other long running processes is not appropriate + for udev; the forked processes, detached or not, will be unconditionally + killed after the event handling has finished.</para> + </listitem> + </varlistentry> + + <varlistentry> + <term><option>LABEL</option></term> + <listitem> + <para>A named label to which a GOTO may jump.</para> + </listitem> + </varlistentry> + + <varlistentry> + <term><option>GOTO</option></term> + <listitem> + <para>Jumps to the next LABEL with a matching name.</para> + </listitem> + </varlistentry> + + <varlistentry> + <term><option>IMPORT{<replaceable>type</replaceable>}</option></term> + <listitem> + <para>Import a set of variables as device properties, + depending on <replaceable>type</replaceable>:</para> + <variablelist> + <varlistentry> + <term><option>program</option></term> + <listitem> + <para>Execute an external program specified as the assigned value and + import its output, which must be in environment key + format. Path specification, command/argument separation, + and quoting work like in <option>RUN</option>.</para> + </listitem> + </varlistentry> + <varlistentry> + <term><option>file</option></term> + <listitem> + <para>Import a text file specified as the assigned value, the content + of which must be in environment key format.</para> + </listitem> + </varlistentry> + <varlistentry> + <term><option>db</option></term> + <listitem> + <para>Import a single property specified as the assigned value from the + current device database. This works only if the database is already populated + by an earlier event.</para> + </listitem> + </varlistentry> + <varlistentry> + <term><option>cmdline</option></term> + <listitem> + <para>Import a single property from the kernel command line. For simple flags + the value of the property is set to '1'.</para> + </listitem> + </varlistentry> + <varlistentry> + <term><option>parent</option></term> + <listitem> + <para>Import the stored keys from the parent device by reading + the database entry of the parent device. The value assigned to + <option>IMPORT{parent}</option> is used as a filter of key names + to import (with the same shell-style pattern matching used for + comparisons).</para> + </listitem> + </varlistentry> + </variablelist> + <para>This can only be used for very short-running foreground tasks. For details + see <option>RUN</option>.</para> + </listitem> + </varlistentry> + + <varlistentry> + <term><option>WAIT_FOR</option></term> + <listitem> + <para>Wait for a file to become available or until a timeout of + 10 seconds expires. The path is relative to the sysfs device; + if no path is specified, this waits for an attribute to appear.</para> + </listitem> + </varlistentry> + + <varlistentry> + <term><option>OPTIONS</option></term> + <listitem> + <para>Rule and device options:</para> + <variablelist> + <varlistentry> + <term><option>link_priority=<replaceable>value</replaceable></option></term> + <listitem> + <para>Specify the priority of the created symlinks. Devices with higher + priorities overwrite existing symlinks of other devices. The default is 0.</para> + </listitem> + </varlistentry> + <varlistentry> + <term><option>event_timeout=</option></term> + <listitem> + <para>Number of seconds an event waits for operations to finish before + giving up and terminating itself.</para> + </listitem> + </varlistentry> + <varlistentry> + <term><option>string_escape=<replaceable>none|replace</replaceable></option></term> + <listitem> + <para>Usually control and other possibly unsafe characters are replaced + in strings used for device naming. The mode of replacement can be specified + with this option.</para> + </listitem> + </varlistentry> + <varlistentry> + <term><option>static_node=</option></term> + <listitem> + <para>Apply the permissions specified in this rule to the static device node with + the specified name. Static device node creation can be requested by kernel modules. + These nodes might not have a corresponding kernel device at the time systemd-udevd is + started; they can trigger automatic kernel module loading.</para> + </listitem> + </varlistentry> + <varlistentry> + <term><option>watch</option></term> + <listitem> + <para>Watch the device node with inotify; when the node is closed after being opened for + writing, a change uevent is synthesized.</para> + </listitem> + </varlistentry> + <varlistentry> + <term><option>nowatch</option></term> + <listitem> + <para>Disable the watching of a device node with inotify.</para> + </listitem> + </varlistentry> + </variablelist> + </listitem> + </varlistentry> + </variablelist> + + <para>The <option>NAME</option>, <option>SYMLINK</option>, <option>PROGRAM</option>, + <option>OWNER</option>, <option>GROUP</option>, <option>MODE</option> and <option>RUN</option> + fields support simple string substitutions. The <option>RUN</option> + substitutions are performed after all rules have been processed, right before the program + is executed, allowing for the use of device properties set by earlier matching + rules. For all other fields, substitutions are performed while the individual rule is + being processed. The available substitutions are:</para> + <variablelist> + <varlistentry> + <term><option>$kernel</option>, <option>%k</option></term> + <listitem> + <para>The kernel name for this device.</para> + </listitem> + </varlistentry> + + <varlistentry> + <term><option>$number</option>, <option>%n</option></term> + <listitem> + <para>The kernel number for this device. For example, 'sda3' has + kernel number of '3'</para> + </listitem> + </varlistentry> + + <varlistentry> + <term><option>$devpath</option>, <option>%p</option></term> + <listitem> + <para>The devpath of the device.</para> + </listitem> + </varlistentry> + + <varlistentry> + <term><option>$id</option>, <option>%b</option></term> + <listitem> + <para>The name of the device matched while searching the devpath upwards for + <option>SUBSYSTEMS</option>, <option>KERNELS</option>, <option>DRIVERS</option> and <option>ATTRS</option>. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><option>$driver</option></term> + <listitem> + <para>The driver name of the device matched while searching the devpath upwards for + <option>SUBSYSTEMS</option>, <option>KERNELS</option>, <option>DRIVERS</option> and <option>ATTRS</option>. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><option>$attr{<replaceable>file</replaceable>}</option>, <option>%s{<replaceable>file</replaceable>}</option></term> + <listitem> + <para>The value of a sysfs attribute found at the device where + all keys of the rule have matched. If the matching device does not have + such an attribute, and a previous KERNELS, SUBSYSTEMS, DRIVERS, or + ATTRS test selected a parent device, then the attribute from that + parent device is used.</para> + <para>If the attribute is a symlink, the last element of the symlink target is + returned as the value.</para> + </listitem> + </varlistentry> + + <varlistentry> + <term><option>$env{<replaceable>key</replaceable>}</option>, <option>%E{<replaceable>key</replaceable>}</option></term> + <listitem> + <para>A device property value.</para> + </listitem> + </varlistentry> + + <varlistentry> + <term><option>$major</option>, <option>%M</option></term> + <listitem> + <para>The kernel major number for the device.</para> + </listitem> + </varlistentry> + + <varlistentry> + <term><option>$minor</option>, <option>%m</option></term> + <listitem> + <para>The kernel minor number for the device.</para> + </listitem> + </varlistentry> + + <varlistentry> + <term><option>$result</option>, <option>%c</option></term> + <listitem> + <para>The string returned by the external program requested with PROGRAM. + A single part of the string, separated by a space character, may be selected + by specifying the part number as an attribute: <option>%c{N}</option>. + If the number is followed by the '+' character, this part plus all remaining parts + of the result string are substituted: <option>%c{N+}</option></para> + </listitem> + </varlistentry> + + <varlistentry> + <term><option>$parent</option>, <option>%P</option></term> + <listitem> + <para>The node name of the parent device.</para> + </listitem> + </varlistentry> + + <varlistentry> + <term><option>$name</option></term> + <listitem> + <para>The current name of the device. If not changed by a rule, it is the + name of the kernel device.</para> + </listitem> + </varlistentry> + + <varlistentry> + <term><option>$links</option></term> + <listitem> + <para>A space-separated list of the current symlinks. The value is + only set during a remove event or if an earlier rule assigned a value.</para> + </listitem> + </varlistentry> + + <varlistentry> + <term><option>$root</option>, <option>%r</option></term> + <listitem> + <para>The udev_root value.</para> + </listitem> + </varlistentry> + + <varlistentry> + <term><option>$sys</option>, <option>%S</option></term> + <listitem> + <para>The sysfs mount point.</para> + </listitem> + </varlistentry> + + <varlistentry> + <term><option>$devnode</option>, <option>%N</option></term> + <listitem> + <para>The name of the device node.</para> + </listitem> + </varlistentry> + + <varlistentry> + <term><option>%%</option></term> + <listitem> + <para>The '%' character itself.</para> + </listitem> + </varlistentry> + + <varlistentry> + <term><option>$$</option></term> + <listitem> + <para>The '$' character itself.</para> + </listitem> + </varlistentry> + </variablelist> + </refsect2> + </refsect1> + + <refsect1> + <title>See Also</title> + <para><citerefentry> + <refentrytitle>systemd-udevd.service</refentrytitle><manvolnum>8</manvolnum> + </citerefentry>, + <citerefentry> + <refentrytitle>udevadm</refentrytitle><manvolnum>8</manvolnum> + </citerefentry></para> + </refsect1> +</refentry> |