UDEVADM(8)                                             UDEVADM(8)

     NAME
          udevadm - udev management tool

     SYNOPSIS
          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
          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
          -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

     Page 1                     systemd 247          (printed 5/25/22)

     UDEVADM(8)                                             UDEVADM(8)

              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.

     Page 2                     systemd 247          (printed 5/25/22)

     UDEVADM(8)                                             UDEVADM(8)

          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

     Page 3                     systemd 247          (printed 5/25/22)

     UDEVADM(8)                                             UDEVADM(8)

              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=TAG
              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.

     Page 4                     systemd 247          (printed 5/25/22)

     UDEVADM(8)                                             UDEVADM(8)

          -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-level=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

     Page 5                     systemd 247          (printed 5/25/22)

     UDEVADM(8)                                             UDEVADM(8)

              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

     Page 6                     systemd 247          (printed 5/25/22)

     UDEVADM(8)                                             UDEVADM(8)

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

     Page 7                     systemd 247          (printed 5/25/22)