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
           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.

       The generated output shows the current device database entry in a terse format. Each line shown is
       prefixed with one of the following characters:

       Table 1. udevadm info output prefixes
       ┌───────┬──────────────────────────────┐
       │Prefix │ Meaning                      │
       ├───────┼──────────────────────────────┤
       │"P:"   │ Device path in /sys/         │
       ├───────┼──────────────────────────────┤
       │"N:"   │ Kernel device node name      │
       ├───────┼──────────────────────────────┤
       │"L:"   │ Device node symlink priority │
       ├───────┼──────────────────────────────┤
       │"S:"   │ Device node symlink          │
       ├───────┼──────────────────────────────┤
       │"E:"   │ Device property              │
       └───────┴──────────────────────────────┘

   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.

       -q, --quiet
           Suppress error logging in triggering events.

       -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=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.

       --uuid
           Trigger the synthetic device events, and associate a randomized UUID with each. These UUIDs are
           printed to standard output, one line for each event. These UUIDs are included in the uevent
           environment block (in the "SYNTH_UUID=" property) and may be used to track delivery of the generated
           events.

       --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-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
           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

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