UDEVADM(8)

NAME
udevadm - udev management tool

SYNOPSIS

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

udevadm info options

udevadm trigger [options]

udevadm settle [options]

udevadm control command

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

--debug
    Print debug messages to standard error.

--version
    Print version number.

-h, --help
    Print help text.

  udevadm info [options] [devpath|file]

Queries the udev database for device information stored in the udev database. It can also query the properties of a device from its sysfs representation to help creating udev rules that match this device.

-q, --query=TYPE
    Query the database for the specified type of device data. It needs the --path or --name to identify the specified device. 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. Note that this option usually is not very useful, since udev can guess the type of the argument, so udevadm --devpath=/class/block/sda is equivalent to udevadm /sys/class/block/sda.

-n, --name=FILE
    The name of the device node or a symlink to query, e.g. [/dev]/sda. Note that this option usually is not very useful, since udev can guess the type of the argument, so udevadm --name=sda is equivalent to udevadm /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.

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

-d, --device-id-of-file=FILE
    Print major/minor numbers of the underlying device, where the file lives on.

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

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

--version
    Print version.

-h, --help
    Print help text.

In addition, an optional positional argument can be used to specify a device name or a sys path. It must start with /dev or /sys respectively.

  udevadm trigger [options] [devpath|file...]

Request device events from the kernel. Primarily used to replay events at system coldplug time.

-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. The default value is change.

-s, --subsystem-match=SUBSYSTEM
    Trigger events for devices which belong to a matching subsystem. This option can be specified multiple times and supports shell style pattern matching.

-S, --subsystem-nomatch=SUBSYSTEM
    Do not trigger events for devices which belong to a matching subsystem. This option can be specified multiple times and supports shell style pattern matching.

-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. This option can be specified multiple times.

-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. This option can be specified multiple times.

-p, --property-match=PROPERTY=VALUE
    Trigger events for devices with a matching property value. This option can be specified multiple times and supports shell style pattern matching.

-g, --tag-match=PROPERTY
    Trigger events for devices with a matching tag. This option can be specified multiple times.

-y, --sysname-match=PATH
    Trigger events for devices with a matching sys device path. This option can be specified multiple times and supports shell style pattern matching.

--name-match=NAME
    Trigger events for devices with a matching device path. This option can be specified multiple times.

-b, --parent-match=SYSPATH
    Trigger events for all children of a given device.

-h, --help
    Print help text.

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.

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

-h, --help
    Print help text.

  udevadm control command

Modify the internal state of the running udev daemon.

-x, --exit
    Signal and wait for systemd-udevd to exit.

-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.

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

-h, --help
    Print help text.

  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 events by subsystem[/devtype]. Only udev events with a matching subsystem value will pass.

-t, --tag-match=string
    Filter events by property. Only udev events with a given tag attached will pass.

-h, --help
    Print help text.

  udevadm test [options] [devpath]

Simulate a udev event run for the given device, and print debug output.

-a, --action=string
    The action string.

-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 help text.

  udevadm test-builtin [options] [command] [devpath]

Run a built-in command COMMAND for device DEVPATH, and print debug output.

-h, --help
    Print help text.

SEE ALSO

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