From 3e2147858f21943d5f4a781c60f33ac22c6096ed Mon Sep 17 00:00:00 2001 From: Kay Sievers Date: Tue, 3 Apr 2012 21:24:46 +0200 Subject: move imported udev into place --- man/udev.xml | 695 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 695 insertions(+) create mode 100644 man/udev.xml (limited to 'man/udev.xml') diff --git a/man/udev.xml b/man/udev.xml new file mode 100644 index 0000000000..8eb583a823 --- /dev/null +++ b/man/udev.xml @@ -0,0 +1,695 @@ + + + + + + + udev + udev + + + + udev + 7 + + + + udev + Linux dynamic device management + + + Description + udev supplies the system software with device events, manages permissions + of device nodes and may create additional symlinks in the /dev + 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. + + The udev daemon, udevd + 8, 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. + + 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. + + + Configuration + udev configuration files are placed in /etc/udev + and /usr/lib/udev. All empty lines or lines beginning with + '#' are ignored. + + Configuration file + udev expects its main configuration file at /etc/udev/udev.conf. + It consists of a set of variables allowing the user to override default udev values. + The following variables can be set: + + + + + Specifies where to place the device nodes in the filesystem. + The default value is /dev. + + + + + + + The logging priority. Valid values are the numerical syslog priorities + or their textual representations: , + and . + + + + + + Rules files + The udev rules are read from the files located in the + system rules directory /usr/lib/udev/rules.d, + the volatile runtime directory /run/udev/rules.d + and the local administration directory /etc/udev/rules.d. + 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 /etc + have the highest priority, files in /run take precedence + over files with the same name in /lib. This can be + used to override a system-supplied rules file with a local file if needed; + a symlink in /etc with the same name as a rules file in + /lib, pointing to /dev/null, + disables the rules file entirely. + + Rule files must have the extension .rules; other + extensions are ignored. + + Every line in the rules file contains at least one key-value pair. + There are two kind 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. + + 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. + + 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: + + + + + Compare for equality. + + + + + + + Compare for inequality. + + + + + + + Assign a value to a key. Keys that represent a list are reset + and only this single value is assigned. + + + + + + + Add the value to a key that holds a list of entries. + + + + + + + Assign a value to a key finally; disallow any later changes. + + + + + 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. + + + + + Match the name of the event action. + + + + + + + Match the devpath of the event device. + + + + + + + Match the name of the event device. + + + + + + + Match the name of a network interface. It can be used once the + NAME key has been set in one of the preceding rules. + + + + + + + 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. + + + + + + + + Match the subsystem of the event device. + + + + + + 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. + + + + + + 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. + + + + + + + + Search the devpath upwards for a matching device name. + + + + + + + Search the devpath upwards for a matching device subsystem name. + + + + + + + Search the devpath upwards for a matching device driver name. + + + + + + + Search the devpath upwards for a device with matching sysfs attribute values. + If multiple 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. + + + + + + + Search the devpath upwards for a device with matching tag. + + + + + + + Match against a device property value. + + + + + + + Match against a device tag. + + + + + + + Test the existence of a file. An octal mode mask can be specified + if needed. + + + + + + + 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. + + + + + + + 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. + + + + + Most of the fields support shell-style pattern matching. The following + pattern characters are supported: + + + + + Matches zero or more characters. + + + + + + Matches any single character. + + + + + + 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. + + + + + The following keys can get values assigned: + + + + + The name to use for a network interface. The name of a device node + can not be changed by udev, only additional symlinks can be created. + + + + + + + The name of a symlink targeting the node. Every matching rule adds + this value to the list of symlinks to be created. 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. Also, symlink names must + never conflict with the kernel's default device node names, as that would + result in unpredictable behavior. + + + + + + + + The permissions for the device node. Every specified value overrides + the compiled-in default value. + + + + + + + The value that should be written to a sysfs attribute of the + event device. + + + + + + + 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). + + + + + + + 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. + + + + + + + Add a program to the list of programs to be executed for a specific + device. + 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. + This can only be used for very short running tasks. Running an + event process for a long period of time may block all further events for + this or a dependent device. Starting daemons or other long running processes + is not appropriate for udev. + + + + + + + A named label to which a GOTO may jump. + + + + + + + Jumps to the next LABEL with a matching name. + + + + + + + Import a set of variables as device properties, + depending on type: + + + + + 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 . + + + + + + Import a text file specified as the assigned value, the content + of which must be in environment key format. + + + + + + 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. + + + + + + Import a single property from the kernel command line. For simple flags + the value of the property is set to '1'. + + + + + + Import the stored keys from the parent device by reading + the database entry of the parent device. The value assigned to + is used as a filter of key names + to import (with the same shell-style pattern matching used for + comparisons). + + + + + + + + + + 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. + + + + + + + Rule and device options: + + + + + Specify the priority of the created symlinks. Devices with higher + priorities overwrite existing symlinks of other devices. The default is 0. + + + + + + Number of seconds an event waits for operations to finish before + giving up and terminating itself. + + + + + + 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. + + + + + + Apply the permissions specified in this rule to the static device node with + the specified name. Static device nodes might be provided by kernel modules + or copied from /usr/lib/udev/devices. These nodes might not have + a corresponding kernel device at the time udevd is started; they can trigger + automatic kernel module loading. + + + + + + Watch the device node with inotify; when the node is closed after being opened for + writing, a change uevent is synthesized. + + + + + + Disable the watching of a device node with inotify. + + + + + + + + The , , , + , , and + fields support simple string substitutions. The + 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: + + + , + + The kernel name for this device. + + + + + , + + The kernel number for this device. For example, 'sda3' has + kernel number of '3' + + + + + , + + The devpath of the device. + + + + + , + + The name of the device matched while searching the devpath upwards for + , , and . + + + + + + + + The driver name of the device matched while searching the devpath upwards for + , , and . + + + + + + , + + 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. + If the attribute is a symlink, the last element of the symlink target is + returned as the value. + + + + + , + + A device property value. + + + + + , + + The kernel major number for the device. + + + + + , + + The kernel minor number for the device. + + + + + , + + 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: . + If the number is followed by the '+' character, this part plus all remaining parts + of the result string are substituted: + + + + + , + + The node name of the parent device. + + + + + + + The current name of the device. If not changed by a rule, it is the + name of the kernel device. + + + + + + + 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. + + + + + , + + The udev_root value. + + + + + , + + The sysfs mount point. + + + + + , + + The name of the device node. + + + + + + + The '%' character itself. + + + + + + + The '$' character itself. + + + + + + + Author + Written by Greg Kroah-Hartman greg@kroah.com and + Kay Sievers kay.sievers@vrfy.org. With much help from + Dan Stekloff and many others. + + + + See Also + + udevd8 + , + + udevadm8 + + + -- cgit v1.2.3-54-g00ecf