+The default install location of the 'udevadm' tool moved from 'sbin'
+to /usr/bin. Some tools expect udevadm in 'sbin', a symlink to udevadm
+needs to be manually created if needed, or --bindir=/sbin be specified.
+
+The expected value of '--libexecdir=' has changed and must no longer contain
+the 'udev' directory.
+
+Kernel modules are now loaded directly by linking udev to 'libkmod'. The
+'modprobe' tool is no longer executed by udev.
+
+The 'blkid' tool is no longer executed from udev rules. Udev links
+directly to libblkid now.
+
+Firmware is loaded natively by udev now, the external 'firmware' binary
+is no longer used.
+
+All built-in tools can be listed and tested with 'udevadm test-builtin'.
+
+The 'udevadm control --reload-rules' option has been renamed to '--reload'.
+It now also reloads the kernel module configuration.
+
+The systemd socket files use PassCredentials=yes, which is available in
+systemd version 38.