systemd-udevd.service

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## Name

systemd-udevd.service, systemd-udevd-control.socket, systemd-udevd-kernel.socket, systemd-udevd — Device event managing daemon

## Synopsis

`systemd-udevd.service`

`systemd-udevd-control.socket`

`systemd-udevd-kernel.socket`

`/usr/lib/systemd/systemd-udevd` [`--daemon`] [`--debug`] [`--children-max=`] [`--exec-delay=`] [`--resolve-names=early|late|never`] [`--version`] [`--help`]

## Description

systemd-udevd listens to kernel uevents. For every event, systemd-udevd executes matching instructions specified in udev rules. See udev(7).

The behavior of the running daemon can be changed with udevadm control.

## Options

`--daemon`

  Detach and run in the background.

`--debug`

  Print debug messages to standard error.

`--children-max=`

  Limit the number of events executed in parallel.

`--exec-delay=`

  Delay the execution of `RUN` instructions by the given number of seconds. This option might be useful when debugging system crashes during coldplug caused by loading non-working kernel modules.

`--resolve-names=`

  Specify when systemd-udevd 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.

`--help`

  Print a short help text and exit.

`--version`

  Print a short version string and exit.

## Environment

`$UDEV_LOG=`

  Set the logging priority.

## Kernel command line

Parameters starting with "rd." will be read when systemd-udevd is used in an initrd.

`udev.log-priority=`, `rd.udev.log-priority=`

  Set the logging priority.

`udev.children-max=`, `rd.udev.children-max=`

  Limit the number of events executed in parallel.

`udev.exec-delay=`, `rd.udev.exec-delay=`

  Delay the execution of `RUN` instructions by the given number of seconds. This option might be useful when debugging system crashes during coldplug caused by loading non-working kernel modules.

`net.ifnames=`

  Network interfaces are renamed to give them predictable names when possible. It is enabled by default; specifying 0 disables it.

## Configuration file

udev expects its main configuration file at `/etc/udev/udev.conf`. It consists of a set of variables allowing the user to override default udev values. All empty lines or lines beginning with '#' are ignored. The following variables can be set:

`udev_log`

  The logging priority. Valid values are the numerical syslog priorities or their textual representations: `err`, `info` and `debug`.

## See Also

udev(7), udevadm(8)