Linux 101 : UDEV, the device manager
Udev is managed by systemd. It also handles loadable modules for hardware devices.
The configuration files for udev are called rules and they live in the "/etc/udev/rules.d" directory.
We could for example order the system to run a specific utility or create a symbolic links when a device is plugged using these rules.
The rules could live in different directories, but the "/etc/udev/rules.d" directory takes precedence over the other locations such as the "/usr/lib/udev/rules.d" directory.
For example rules in the "40-mouse.rules" file in "/etc/udev/rules.d" will take precedence over the default "40-mouse.rules" file in "/usr/lib/udev/rules.d".
We could also find rules in "/run/udev/rules.d" that are generated on each boot - we find there temporary rules that won't survive a reboot -.
To manage udev, we could use a utility program called "udevadm".
For example, we could use it to get information about the "/dev/sdb" drive using the below command:
The information include the device's vendor ID, product ID, model, major and minor numbers, ...
We could also monitor all the udev events using the below command:
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