I installed OL 7.4 in VirtualBox yesterday, using the default minimal server install and found the following in syslog, which was triggered during a yum update.
Aug 13 14:30:29 vm702 dracut: Executing: /sbin/dracut -f /boot/initramfs-4.1.12-94.5.7.el7uek.x86_64.img 4.1.12-94.5.7.el7uek.x86_64
Aug 13 14:30:31 vm702 dracut: dracut module 'mdraid' will not be installed, because command 'mdadm' could not be found!
Obviously this is happening because mdadm is not installed:
# yum list mdadm
Loaded plugins: ulninfo
Available Packages
mdadm.x86_64 4.0-5.el7 ol7_latest
I'm not saying that there is necessarily a problem, but I wonder why support for such a well-known and essential module is not installed by default. I'm not aware that mdadm has suddenly become obsolete, or that removing it saves any resources worth mentioning. It appears that the Oracle UEK4 kernel tries to include several modules, but the default installation did not include the necessary software, as shown below in the /var/log/messages log file.
Aug 14 06:44:29 vm702 dracut: dracut-
Aug 14 06:44:29 vm702 dracut: Executing: /sbin/dracut -f /boot/initramfs-4.1.12-94.5.7.el7uek.x86_64.img 4.1.12-94.5.7.el7uek.x86_64
Aug 14 06:44:30 vm702 dracut: dracut module 'busybox' will not be installed, because command 'busybox' could not be found!
Aug 14 06:44:30 vm702 dracut: dracut module 'crypt' will not be installed, because command 'cryptsetup' could not be found!
Aug 14 06:44:30 vm702 dracut: dracut module 'dmraid' will not be installed, because command 'dmraid' could not be found!
Aug 14 06:44:30 vm702 dracut: dracut module 'mdraid' will not be installed, because command 'mdadm' could not be found!
Aug 14 06:44:30 vm702 dracut: dracut module 'multipath' will not be installed, because command 'multipath' could not be found!
Aug 14 06:44:30 vm702 dracut: dracut module 'cifs' will not be installed, because command 'mount.cifs' could not be found!
Aug 14 06:44:30 vm702 dracut: dracut module 'iscsi' will not be installed, because command 'iscsistart' could not be found!
Aug 14 06:44:30 vm702 dracut: dracut module 'iscsi' will not be installed, because command 'iscsi-iname' could not be found!
Aug 14 06:44:30 vm702 dracut: dracut module 'busybox' will not be installed, because command 'busybox' could not be found!
Aug 14 06:44:30 vm702 dracut: dracut module 'crypt' will not be installed, because command 'cryptsetup' could not be found!
Aug 14 06:44:30 vm702 dracut: dracut module 'dmraid' will not be installed, because command 'dmraid' could not be found!
Aug 14 06:44:30 vm702 dracut: dracut module 'mdraid' will not be installed, because command 'mdadm' could not be found!
Aug 14 06:44:30 vm702 dracut: dracut module 'multipath' will not be installed, because command 'multipath' could not be found!
Aug 14 06:44:30 vm702 dracut: dracut module 'cifs' will not be installed, because command 'mount.cifs' could not be found!
Aug 14 06:44:30 vm702 dracut: dracut module 'iscsi' will not be installed, because command 'iscsistart' could not be found!
Aug 14 06:44:30 vm702 dracut: dracut module 'iscsi' will not be installed, because command 'iscsi-iname' could not be found!
Aug 14 06:44:31 vm702 dracut: *** Including module: bash ***
Aug 14 06:44:31 vm702 dracut: *** Including module: nss-softokn ***
Aug 14 06:44:31 vm702 dracut: *** Including module: i18n ***
Aug 14 06:44:31 vm702 dracut: *** Including module: network ***
Aug 14 06:44:32 vm702 dracut: *** Including module: ifcfg ***
Aug 14 06:44:32 vm702 dracut: *** Including module: drm ***
Aug 14 06:44:32 vm702 dracut: *** Including module: plymouth ***
Aug 14 06:44:33 vm702 dracut: *** Including module: dm ***
Aug 14 06:44:33 vm702 dracut: Skipping udev rule: 64-device-mapper.rules
Aug 14 06:44:33 vm702 dracut: Skipping udev rule: 60-persistent-storage-dm.rules
Aug 14 06:44:33 vm702 dracut: Skipping udev rule: 55-dm.rules
Aug 14 06:44:33 vm702 dracut: *** Including module: kernel-modules ***
Aug 14 06:44:38 vm702 dracut: *** Including module: lvm ***
Aug 14 06:44:38 vm702 dracut: Skipping udev rule: 64-device-mapper.rules
Aug 14 06:44:38 vm702 dracut: Skipping udev rule: 56-lvm.rules
Aug 14 06:44:38 vm702 dracut: Skipping udev rule: 60-persistent-storage-lvm.rules
Aug 14 06:44:38 vm702 dracut: *** Including module: qemu ***
Aug 14 06:44:38 vm702 dracut: *** Including module: resume ***
Aug 14 06:44:38 vm702 dracut: *** Including module: rootfs-block ***
Aug 14 06:44:38 vm702 dracut: *** Including module: terminfo ***
Aug 14 06:44:38 vm702 dracut: *** Including module: udev-rules ***
Aug 14 06:44:38 vm702 dracut: Skipping udev rule: 40-redhat-cpu-hotplug.rules
Aug 14 06:44:38 vm702 dracut: Skipping udev rule: 91-permissions.rules
Aug 14 06:44:38 vm702 dracut: *** Including module: biosdevname ***
Aug 14 06:44:38 vm702 dracut: *** Including module: systemd ***
Aug 14 06:44:39 vm702 dracut: *** Including module: usrmount ***
Aug 14 06:44:39 vm702 dracut: *** Including module: base ***
Aug 14 06:44:39 vm702 dracut: *** Including module: fs-lib ***
Aug 14 06:44:39 vm702 dracut: *** Including module: shutdown ***
Aug 14 06:44:39 vm702 dracut: *** Including modules done ***
Aug 14 06:44:39 vm702 dracut: *** Installing kernel module dependencies and firmware ***
Aug 14 06:44:39 vm702 dracut: *** Installing kernel module dependencies and firmware done ***
Aug 14 06:44:39 vm702 dracut: *** Resolving executable dependencies ***
Aug 14 06:44:40 vm702 dracut: *** Resolving executable dependencies done***
Aug 14 06:44:40 vm702 dracut: *** Hardlinking files ***
Aug 14 06:44:40 vm702 dracut: *** Hardlinking files done ***
Aug 14 06:44:40 vm702 dracut: *** Stripping files ***
Aug 14 06:44:40 vm702 dracut: *** Stripping files done ***
Aug 14 06:44:40 vm702 dracut: *** Generating early-microcode cpio image contents ***
Aug 14 06:44:40 vm702 dracut: *** Constructing GenuineIntel.bin ****
Aug 14 06:44:40 vm702 dracut: *** Store current command line parameters ***
Aug 14 06:44:40 vm702 dracut: *** Creating image file ***
Aug 14 06:44:40 vm702 dracut: *** Creating microcode section ***
Aug 14 06:44:40 vm702 dracut: *** Created microcode section ***
Aug 14 06:44:50 vm702 dracut: *** Creating image file done ***
Aug 14 06:44:56 vm702 dracut: *** Creating initramfs image file '/boot/initramfs-4.1.12-94.5.7.el7uek.x86_64.img' done ***