udevadm(8) — Linux manual page

NAME | SYNOPSIS | DESCRIPTION | OPTIONS | SEE ALSO | COLOPHON

UDEVADM(8)                         udevadm                        UDEVADM(8)

NAME         top

       udevadm - udev management tool

SYNOPSIS         top

       udevadm [--debug] [--version] [--help]

       udevadm info [options] [devpath]

       udevadm trigger [options] [devpath]

       udevadm settle [options]

       udevadm control option

       udevadm monitor [options]

       udevadm test [options] devpath

       udevadm test-builtin [options] command devpath

DESCRIPTION         top

       udevadm expects a command and command specific options. It controls
       the runtime behavior of systemd-udevd, requests kernel events,
       manages the event queue, and provides simple debugging mechanisms.

OPTIONS         top

       -d, --debug
           Print debug messages to standard error. This option is implied in
           udevadm test and udevadm test-builtin commands.

       -h, --help
           Print a short help text and exit.

   udevadm info [options] [devpath|file|unit...]
       Query the udev database for device information.

       Positional arguments should be used to specify one or more devices.
       Each one may be a device name (in which case it must start with
       /dev/), a sys path (in which case it must start with /sys/), or a
       systemd device unit name (in which case it must end with ".device",
       see systemd.device(5)).

       -q, --query=TYPE
           Query the database for the specified type of device data. Valid
           TYPEs are: name, symlink, path, property, all.

       -p, --path=DEVPATH
           The /sys path of the device to query, e.g.
           [/sys]/class/block/sda. This option is an alternative to the
           positional argument with a /sys/ prefix.  udevadm info
           --path=/class/block/sda is equivalent to udevadm info
           /sys/class/block/sda.

       -n, --name=FILE
           The name of the device node or a symlink to query, e.g.
           [/dev]/sda. This option is an alternative to the positional
           argument with a /dev/ prefix.  udevadm info --name=sda is
           equivalent to udevadm info /dev/sda.

       -r, --root
           Print absolute paths in name or symlink query.

       -a, --attribute-walk
           Print all sysfs properties of the specified device that can be
           used in udev rules to match the specified device. It prints all
           devices along the chain, up to the root of sysfs that can be used
           in udev rules.

       -x, --export
           Print output as key/value pairs. Values are enclosed in single
           quotes. This takes effects only when --query=property or
           --device-id-of-file=FILE is specified.

       -P, --export-prefix=NAME
           Add a prefix to the key name of exported values. This implies
           --export.

       -d, --device-id-of-file=FILE
           Print major/minor numbers of the underlying device, where the
           file lives on. If this is specified, all positional arguments are
           ignored.

       -e, --export-db
           Export the content of the udev database.

       -c, --cleanup-db
           Cleanup the udev database.

       -w[SECONDS], --wait-for-initialization[=SECONDS]
           Wait for device to be initialized. If argument SECONDS is not
           specified, the default is to wait forever.

       -h, --help
           Print a short help text and exit.

   udevadm trigger [options] [devpath|file|unit]
       Request device events from the kernel. Primarily used to replay
       events at system coldplug time.

       Takes device specifications as positional arguments. See the
       description of info above.

       -v, --verbose
           Print the list of devices which will be triggered.

       -n, --dry-run
           Do not actually trigger the event.

       -t, --type=TYPE
           Trigger a specific type of devices. Valid types are: devices,
           subsystems. The default value is devices.

       -c, --action=ACTION
           Type of event to be triggered. Possible actions are "add",
           "remove", "change", "move", "online", "offline", "bind", and
           "unbind". Also, the special value "help" can be used to list the
           possible actions. The default value is "change".

       -s, --subsystem-match=SUBSYSTEM
           Trigger events for devices which belong to a matching subsystem.
           This option supports shell style pattern matching. When this
           option is specified more than once, then each matching result is
           ORed, that is, all the devices in each subsystem are triggered.

       -S, --subsystem-nomatch=SUBSYSTEM
           Do not trigger events for devices which belong to a matching
           subsystem. This option supports shell style pattern matching.
           When this option is specified more than once, then each matching
           result is ANDed, that is, devices which do not match all
           specified subsystems are triggered.

       -a, --attr-match=ATTRIBUTE=VALUE
           Trigger events for devices with a matching sysfs attribute. If a
           value is specified along with the attribute name, the content of
           the attribute is matched against the given value using shell
           style pattern matching. If no value is specified, the existence
           of the sysfs attribute is checked. When this option is specified
           multiple times, then each matching result is ANDed, that is, only
           devices which have all specified attributes are triggered.

       -A, --attr-nomatch=ATTRIBUTE=VALUE
           Do not trigger events for devices with a matching sysfs
           attribute. If a value is specified along with the attribute name,
           the content of the attribute is matched against the given value
           using shell style pattern matching. If no value is specified, the
           existence of the sysfs attribute is checked. When this option is
           specified multiple times, then each matching result is ANDed,
           that is, only devices which have none of the specified attributes
           are triggered.

       -p, --property-match=PROPERTY=VALUE
           Trigger events for devices with a matching property value. This
           option supports shell style pattern matching. When this option is
           specified more than once, then each matching result is ORed, that
           is, devices which have one of the specified properties are
           triggered.

       -g, --tag-match=PROPERTY
           Trigger events for devices with a matching tag. When this option
           is specified multiple times, then each matching result is ANDed,
           that is, devices which have all specified tags are triggered.

       -y, --sysname-match=NAME
           Trigger events for devices for which the last component (i.e. the
           filename) of the /sys path matches the specified PATH. This
           option supports shell style pattern matching. When this option is
           specified more than once, then each matching result is ORed, that
           is, all devices which have any of the specified NAME are
           triggered.

       --name-match=NAME
           Trigger events for devices with a matching device path. When this
           option is specified more than once, then each matching result is
           ORed, that is, all specified devices are triggered.

       -b, --parent-match=SYSPATH
           Trigger events for all children of a given device. When this
           option is specified more than once, then each matching result is
           ORed, that is, all children of each specified device are
           triggered.

       -w, --settle
           Apart from triggering events, also waits for those events to
           finish. Note that this is different from calling udevadm settle.
           udevadm settle waits for all events to finish. This option only
           waits for events triggered by the same command to finish.

       --wait-daemon[=SECONDS]
           Before triggering uevents, wait for systemd-udevd daemon to be
           initialized. Optionally takes timeout value. Default timeout is 5
           seconds. This is equivalent to invoke invoking udevadm control
           --ping before udevadm trigger.

       -h, --help
           Print a short help text and exit.

       In addition, optional positional arguments can be used to specify
       device names or sys paths. They must start with /dev or /sys
       respectively.

   udevadm settle [options]
       Watches the udev event queue, and exits if all current events are
       handled.

       -t, --timeout=SECONDS
           Maximum number of seconds to wait for the event queue to become
           empty. The default value is 120 seconds. A value of 0 will check
           if the queue is empty and always return immediately. A non-zero
           value will return an exit code of 0 if queue became empty before
           timeout was reached, non-zero otherwise.

       -E, --exit-if-exists=FILE
           Stop waiting if file exists.

       -h, --help
           Print a short help text and exit.

       See systemd-udev-settle.service(8) for more information.

   udevadm control option
       Modify the internal state of the running udev daemon.

       -e, --exit
           Signal and wait for systemd-udevd to exit. No option except for
           --timeout can be specified after this option. Note that
           systemd-udevd.service contains Restart=always and so as a result,
           this option restarts systemd-udevd. If you want to stop
           systemd-udevd.service, please use the following:

               systemctl stop systemd-udevd-control.socket systemd-udevd-kernel.socket systemd-udevd.service

       -l, --log-priority=value
           Set the internal log level of systemd-udevd. Valid values are the
           numerical syslog priorities or their textual representations:
           emerg, alert, crit, err, warning, notice, info, and debug.

       -s, --stop-exec-queue
           Signal systemd-udevd to stop executing new events. Incoming
           events will be queued.

       -S, --start-exec-queue
           Signal systemd-udevd to enable the execution of events.

       -R, --reload
           Signal systemd-udevd to reload the rules files and other
           databases like the kernel module index. Reloading rules and
           databases does not apply any changes to already existing devices;
           the new configuration will only be applied to new events.

       -p, --property=KEY=value
           Set a global property for all events.

       -m, --children-max=value
           Set the maximum number of events, systemd-udevd will handle at
           the same time.

       --ping
           Send a ping message to systemd-udevd and wait for the reply. This
           may be useful to check that systemd-udevd daemon is running.

       -t, --timeout=seconds
           The maximum number of seconds to wait for a reply from
           systemd-udevd.

       -h, --help
           Print a short help text and exit.

   udevadm monitor [options]
       Listens to the kernel uevents and events sent out by a udev rule and
       prints the devpath of the event to the console. It can be used to
       analyze the event timing, by comparing the timestamps of the kernel
       uevent and the udev event.

       -k, --kernel
           Print the kernel uevents.

       -u, --udev
           Print the udev event after the rule processing.

       -p, --property
           Also print the properties of the event.

       -s, --subsystem-match=string[/string]
           Filter kernel uevents and udev events by subsystem[/devtype].
           Only events with a matching subsystem value will pass. When this
           option is specified more than once, then each matching result is
           ORed, that is, all devices in the specified subsystems are
           monitored.

       -t, --tag-match=string
           Filter udev events by tag. Only udev events with a given tag
           attached will pass. When this option is specified more than once,
           then each matching result is ORed, that is, devices which have
           one of the specified tags are monitored.

       -h, --help
           Print a short help text and exit.

   udevadm test [options] [devpath]
       Simulate a udev event run for the given device, and print debug
       output.

       -a, --action=ACTION
           Type of event to be simulated. Possible actions are "add",
           "remove", "change", "move", "online", "offline", "bind", and
           "unbind". Also, the special value "help" can be used to list the
           possible actions. The default value is "add".

       -N, --resolve-names=early|late|never
           Specify when udevadm should resolve names of users and groups.
           When set to early (the default), names will be resolved when the
           rules are parsed. When set to late, names will be resolved for
           every event. When set to never, names will never be resolved and
           all devices will be owned by root.

       -h, --help
           Print a short help text and exit.

   udevadm test-builtin [options] [command] [devpath]
       Run a built-in command COMMAND for device DEVPATH, and print debug
       output.

       -h, --help
           Print a short help text and exit.

SEE ALSO         top

       udev(7), systemd-udevd.service(8)

COLOPHON         top

       This page is part of the systemd (systemd system and service manager)
       project.  Information about the project can be found at 
       ⟨http://www.freedesktop.org/wiki/Software/systemd⟩.  If you have a bug
       report for this manual page, see
       ⟨http://www.freedesktop.org/wiki/Software/systemd/#bugreports⟩.  This
       page was obtained from the project's upstream Git repository
       ⟨https://github.com/systemd/systemd.git⟩ on 2020-08-13.  (At that
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systemd 246                                                       UDEVADM(8)

Pages that refer to this page: systemd.link(5)udev.conf(5)30-systemd-environment-d-generator(7)systemd.directives(7)systemd.index(7)systemd.net-naming-scheme(7)udev(7)dmsetup(8)systemd-udevd(8)systemd-udevd-control.socket(8)systemd-udevd-kernel.socket(8)systemd-udevd.service(8)systemd-udev-settle.service(8)