How to reload udev rules without reboot?

Question

How should one reload udev rules, so that newly created one can function?

I'm running Arch Linux, and I don't have a udevstart command here.

Also checked /etc/rc.d, no udev service there.

Answer 1

# udevadm control --reload-rules

Answer 2

Udev uses the inotify mechanism to watch for changes in the rules directory, in both the library and in the local configuration trees (typically located at /lib/udev/rules.d and /etc/udev/rules.d). So you don't need to do anything when you change a rules file.

You only need to notify the udev daemon explicitly if you're doing something unusual, for example if you have a rule that includes files in another directory. Then you can use the usual convention for asking daemons to reload their configuration: send a SIGHUP (pkill -HUP udevd). Or you can use the udevadm command: udevadm control --reload-rules.

The udev rules are only applied when a device is added. If you want to reapply the rules to a device that is already connected, you need to do this explicitly, by calling udevadm trigger with the right options to match the device(s) whose configuration has changed, e.g. udevadm trigger --attr-match=vendor='Yoyodyne' --attr-match=model='Frobnicator 300'.

Answer 3

Please note that more recent versions of udev have dropped the inotify support so the reloading of the rules on change is needed more often these days.