udev
udev is responsible for dynamic device management needed for hot plugging devices. Information about configured and active devices is contained in the /dev virtual filesystem.
- When a device changes state, the kernel sends an event to the systemd-udevd.service daemon.
- The daemon searches configured rules to match the event
- The udev rules are stored and read from the following locations: (check the
udevmanpage on your system)- /lib/udev/rules.d (system directory)
- /run/udev/rules.d (volatile runtime directory)
- /etc/udev/rules.d (local administration directory)
- If you want to monitor udev events, use the command
udevadm.
/dev
- the /dev virtual filesystem describes the devices on your system.
- The value in the first column represents the type of device it is:
- b : block device (hdd)
- c : character device (terminal, printer, special)
- d : directory
- l : symbolic link