Recognize DM_DISABLE_UDEV environment variable while using LVM2 tools, dmsetup and libdevmapper to fallback to non-udev operation fully. Setting this variable acts as a shortcut for using --noudevsync, --noudevrules and --verifyudev option in dmsetup and setting devices/obtain_device_list_from_udev=0, activation/udev_sync=0 (or --noudevsync LVM2 command line option), activation/udev_rules=0 and activation/verify_udev_operations=1 option in LVM2. Changes also apply for any libdevmapper users.
Setting the DM_DISABLE_UDEV environment variable provides a more convenient way of disabling udev support in libdevmapper, dmsetup and LVM2 tools globally without a need to modify any existing configuration settings. This is mostly useful if the system environment does not use udev.
Result (if any):
Refer to dmsetup manual page and LVM2 manual pages as well as the comments in lvm.conf itself and descriptions of the options mentioned above.