From b750101eb236130cf056c675997decbac904cc49 Mon Sep 17 00:00:00 2001 From: Daniel Baumann Date: Sun, 7 Apr 2024 17:35:18 +0200 Subject: Adding upstream version 252.22. Signed-off-by: Daniel Baumann --- man/udev.xml | 860 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 860 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 0000000..332c7ac --- /dev/null +++ b/man/udev.xml @@ -0,0 +1,860 @@ + + + + + + + + udev + systemd + + + + udev + 7 + + + + udev + 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, systemd-udevd.service + 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. + + + + Rules Files + The udev rules are read from the files located in the system rules directories + /usr/lib/udev/rules.d and /usr/local/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 filenames replace each other. Files in /etc/ have the highest priority, + files in /run/ take precedence over files with the same name under + /usr/. 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 + /usr/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. + Except for empty lines or lines beginning with #, which are ignored. + There are two kinds of keys: match and assignment. + If all match keys match against their values, the rule gets applied and the + assignment keys get the specified values 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-operator-value expressions. + Each expression has a distinct effect, depending on the key and operator used. + + + Operators + + + == + + Compare for equality. (The specified key has the specified value.) + + + + + != + + Compare for inequality. (The specified key doesn't have the specified value, or the + specified key is not present at all.) + + + + + + = + + 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. + + + + + -= + + Remove the value from a key that holds a list of entries. + + + + + := + + Assign a value to a key finally; disallow any later changes. + + + + + + + Values + Values are written as double quoted strings, such as ("string"). + To include a quotation mark (") in the value, precede it by a backslash (\"). + Any other occurrences of a backslash followed by a character are not unescaped. + That is, "\t\n" is treated as four characters: + backslash, lowercase t, backslash, lowercase n. + + The string can be prefixed with a lowercase e (e"string\n") to mark the string as + C-style escaped. + For example, e"string\n" is parsed as 7 characters: 6 lowercase letters and a newline. + This can be useful for writing special characters when a kernel driver requires them. + + Please note that NUL is not allowed in either string variant. + + + + Keys + 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. + + + ACTION + + Match the name of the event action. + + + + + DEVPATH + + Match the devpath of the event device. + + + + + KERNEL + + Match the name of the event device. + + + + + KERNELS + + Search the devpath upwards for a matching device name. + + + + + NAME + + Match the name of a network interface. It can be used once the + NAME key has been set in one of the preceding rules. + + + + + SYMLINK + + 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. If the operator is !=, the token returns true only if there is no + symlink matched. + + + + + SUBSYSTEM + + Match the subsystem of the event device. + + + + + SUBSYSTEMS + + Search the devpath upwards for a matching device subsystem name. + + + + + DRIVER + + 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. + + + + + DRIVERS + + Search the devpath upwards for a matching device driver name. + + + + + ATTR{filename} + + Match sysfs attribute value of the event device. + + Trailing whitespace in the attribute values is ignored unless the specified match value + itself contains trailing whitespace. + + + + + ATTRS{filename} + + Search the devpath upwards for a device with matching sysfs attribute values. If + multiple ATTRS 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. + + + + + SYSCTL{kernel parameter} + + Match a kernel parameter value. + + + + + ENV{key} + + Match against a device property value. + + + + + CONST{key} + + Match against a system-wide constant. Supported keys are: + + + arch + + System's architecture. See in + systemd.unit5 + for possible values. + + + + virt + + System's virtualization environment. See + systemd-detect-virt1 + for possible values. + + + + Unknown keys will never match. + + + + + TAG + + Match against one of device tags. It can be used once a TAG key has been set in one of + the preceding rules. There may be multiple tags; only one needs to match. If the operator is + !=, the token returns true only if there is no tag matched. + + + + + TAGS + + Search the devpath upwards for a device with matching tag. If the operator is + !=, the token returns true only if there is no tag matched. + + + + + TEST{octal mode mask} + + Test the existence of a file. An octal mode mask can be specified + if needed. + + + + + PROGRAM + + 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 standard output is available in the RESULT + key. + + This can only be used for very short-running foreground tasks. For details, see + RUN. + + Note that multiple PROGRAM keys may be specified in one rule, and + =, :=, and += have the same effect as + ==. + + + + + RESULT + + 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 glob pattern matching and + alternate patterns. The following special 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. + + + + | + + Separates alternative patterns. For example, the pattern string + abc|x* would match either abc + or x*. + + + + + The following keys can get values assigned: + + + NAME + + The name to use for a network interface. See + systemd.link5 + for a higher-level mechanism for setting the interface name. + The name of a device node cannot be changed by udev, only additional + symlinks can be created. + + + + + SYMLINK + + The name of a symlink targeting the node. Every matching rule adds + this value to the list of symlinks to be created. + The set of characters to name a symlink is limited. Allowed + characters are 0-9A-Za-z#+-.:=@_/, valid UTF-8 character + sequences, and \x00 hex encoding. All other + characters are replaced by a _ character. + 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. + Symlink names must never conflict with the kernel's default device + node names, as that would result in unpredictable behavior. + + + + + + OWNER, GROUP, MODE + + The permissions for the device node. Every specified value overrides + the compiled-in default value. + + + + + SECLABEL{module} + + Applies the specified Linux Security Module label to the device node. + + + + + ATTR{key} + + The value that should be written to a sysfs attribute of the + event device. + + + + + SYSCTL{kernel parameter} + + The value that should be written to kernel parameter. + + + + + ENV{key} + + 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, for example, the PROGRAM + match key). + + + + + TAG + + 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. + + + + + RUN{type} + + Specify a program to be executed after processing of all the rules for the event. With + +=, this invocation is added to the list, and with = or + :=, it replaces any previous contents of the list. Please note that both + program and builtin types described below share a common + list, so clearing the list with := and = affects both + types. + + type may be: + + + program + + Execute an external program specified as the assigned + value. If no absolute path is given, the program is expected + to live in /usr/lib/udev; otherwise, the + absolute path must be specified. + This is the default if no type + is specified. + + + + builtin + + As program, but use one of the + built-in programs rather than an external one. + + + + + 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 foreground tasks. Running an event process for + a long period of time may block all further events for this or a dependent device. + + Note that running programs that access the network or mount/unmount filesystems is not + allowed inside of udev rules, due to the default sandbox that is enforced on + systemd-udevd.service. + + Starting daemons or other long-running processes is not allowed; the forked processes, + detached or not, will be unconditionally killed after the event handling has finished. In order + to activate long-running processes from udev rules, provide a service unit and pull it in from a + udev device using the SYSTEMD_WANTS device property. See + systemd.device5 + for details. + + + + + LABEL + + A named label to which a GOTO may jump. + + + + + GOTO + + Jumps to the next LABEL with a matching name. + + + + + IMPORT{type} + + Import a set of variables as device properties, depending on + type: + + + + program + + Execute an external program specified as the assigned + value and, if it returns successfully, + import its output, which must be in environment key + format. Path specification, command/argument separation, + and quoting work like in RUN. + + + + builtin + + Similar to program, but use one of the + built-in programs rather than an external one. + + + + file + + Import a text file specified as the assigned value, the content + of which must be in environment key format. + + + + db + + 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. + + + + cmdline + + Import a single property from the kernel command line. For simple flags + the value of the property is set to 1. + + + + parent + + 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 glob pattern matching used for + comparisons). + + + + + This can only be used for very short-running foreground tasks. For details see + . + + Note that multiple IMPORT{} keys may be specified in one rule, and + =, :=, and += have the same effect as + ==. The key is true if the import is successful, unless != + is used as the operator which causes the key to be true if the import failed. + + + + + OPTIONS + + 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. + + + + + + When replace, possibly unsafe characters in strings + assigned to NAME, SYMLINK, and + ENV{key} are replaced. When + none, no replacement is performed. When unset, the replacement + is performed for NAME, SYMLINK, but not for + ENV{key}. Defaults to unset. + + + + + + Apply the permissions specified in this rule to the + static device node with the specified name. Also, for every + tag specified in this rule, create a symlink + in the directory + /run/udev/static_node-tags/tag + pointing at the static device node with the specified name. + Static device node creation is performed by systemd-tmpfiles + before systemd-udevd is started. The static nodes might not + have a corresponding kernel device; they are used to trigger + automatic kernel module loading when they are accessed. + + + + + + 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. + + + + + + Set the flag (sticky bit) on the udev database entry of the event device. Device + properties are then kept in the database even when udevadm info + --cleanup-db is called. This option can be useful in certain cases + (e.g. Device Mapper devices) for persisting device state on the transition from + initrd. + + + + + + Takes a log level name like debug or + info, or a special value reset. When a log + level name is specified, the maximum log level is changed to that level. When + reset is set, then the previously specified log level is + revoked. Defaults to the log level of the main process of + systemd-udevd. + This may be useful when debugging events for certain devices. Note that the + log level is applied when the line including this rule is processed. So, for + debugging, it is recommended that this is specified at earlier place, e.g., the + first line of 00-debug.rules. + Example for debugging uevent processing for network interfaces: + # /etc/udev/rules.d/00-debug-net.rules +SUBSYSTEM=="net", OPTIONS="log_level=debug" + + + + + + + + The NAME, SYMLINK, + PROGRAM, OWNER, + GROUP, MODE, SECLABEL, + and RUN fields support simple string substitutions. + The RUN 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 + 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 , + , , or + 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: %c{N}. + If the number is followed by the + character, this part plus all remaining parts + of the result string are substituted: %c{N+}. + + + + + , + + 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. + + + + + + + + See Also + + + systemd-udevd.service8 + , + + udevadm8 + , + + systemd.link5 + + + + -- cgit v1.2.3