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Systemd-Udev

It detects the hardwere and loads approriate drivers or execute a user defined behavior (ex. auto usb mounts)

  • The rules are stored in /usr/lib/udev/rules.d
  • The custom rules are defined in /etc/udev/rules.d.
  • Then the hardwer gets registered to the /sys dir

Probing the hardwere

See how the system probes particular hardwer 

udevadm monitor
# Output:
# UDEV - the event which udev sends out after rule processing
# KERNEL - the kernel uevent
# KERNEL[132406.831270] add
# /devices/pci0000:00/0000:00:11.0/0000:02:04.0/usb1/1-1 (usb)
# KERNEL[132406.974110] add
# /devices/pci0000:00/0000:00:11.0/0000:02:04.0/usb1/1-1/1-1:1.0 (usb)
# UDEV [132406.988182] add
# /devices/pci0000:00/0000:00:11.0/0000:02:04.0/usb1/1-1 (usb)
# KERNEL[132406.999249] add /module/usb_storage (module)
# UDEV [132407.001203] add /module/usb_storage (module)

Alernative to loading modules

By creating a file in /etc/modules-load.d

  • The one that are already loaded are in the /usr/lib/modules-load.d.