We’re pleased to announce that Red Hat Enterprise Linux Atomic Host 7.4 is now generally available. Red Hat Enterprise Linux Atomic Host is a lightweight, container-optimized version of Red Hat Enterprise Linux. Red Hat Enterprise Linux Atomic Host couples the flexible, modular capabilities of Linux containers with the reliability and security of Red Hat Enterprise Linux in a reduced footprint, to decrease the attack surface and provide only the packages needed to light up hardware and run containers. Here’s a look at some of the major changes in 7.4.
OverlayFS now fully supported with SELinux
After being introduced in Red Hat Enterprise Linux 7.1 as a technology preview, OverlayFS is now fully supported in Red Hat Enterprise Linux 7.4 and Red Hat Enterprise Linux Atomic Host 7.4 when used with docker as the docker graph driver under the conditions described in the release notes.
As the name implies, OverlayFS is a type of file system that allows users to overlay a file system on top of another file system. When changes are made to a file, they are stored in the “upper” file system and the “lower” file system remains unchanged. This is used for Linux containers to allow writes to container images, which may be shared among multiple running containers. This will also convey performance benefits when using OverlayFS, particularly for container builds. Red Hat recommends using the overlay2 graph driver with Linux containers.
With 7.4, OverlayFS now has SELinux support and is fully supported as a graph driver for Linux containers. Note that OverlayFS is still only supported with XFS as the underlying file system, and is not supported for persistent storage for containers. Persistent storage for containers should still be placed on non-OverlayFS volumes to be supported.