udevadm

systemd
Developer Kay Sievers kay@vrfy.org
udevadm 8
udevadm udev management tool
`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`

## 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.

### 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 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: `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 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