udevadm (8)

udevadm [--debug] [--version] [--help] udevadm info options udevadm trigger [options] udevadm settle [options] udevadm control command udevadm monitor [options] udevadm hwdb [options] udevadm test [options] devpath udevadm test-builtin [options] command devpath

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.

--debug

Print debug messages to standard error.

--version

Print version number.

-h, --help

Print help text.

udevadm info [\fIOPTIONS\fR] [\fIDEVPATH\fR|\fIFILE\fR]

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.

udevadm trigger [options]

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=NAME

Trigger events for devices with a matching sys device name. This option can be specified multiple times and supports shell style pattern matching.

-b, --parent-match=SYSPATH

Trigger events for all children of a given device.

-h, --help

Print help text.

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 \fIcommand\fR

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: err, 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 hwdb [options]

Maintain the hardware database index in /etc/udev/hwdb.bin.

-u, --update

Compile the hardware database information located in /usr/lib/udev/hwdb.d/, /etc/udev/hwdb.d/ and store it in /etc/udev/hwdb.bin. This should be done after any update to the source files; it will not be called automatically. The running udev daemon will detect a new database on its own and does not need to be notified about it.

--usr

Put the compiled database into /usr/lib/udev/hwdb.bin instead. Use this if you want to ship a pre-compiled database in immutable system images, or don't use /etc/udev/hwdb.d and want to avoid large binary files in /etc.

-t, --test=string

Query the database with a modalias string, and print the retrieved properties.

-r, --root=string

Alternative root path in the file system for reading and writing files.

-h, --help

Print help text.

udevadm test [options] \fIdevpath\fR

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] \fICOMMAND\fR \fIDEVPATH\fR

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

-h, --help

Print help text.

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