Full name Overlay File System | File system permissions | |
Developer(s) Miklos Szeredi, Open Source Community Supported operating systems | ||
In computing, OverlayFS, a filesystem service for Linux, implements a union mount for other file systems.
It was merged into the Linux kernel mainline in 2014, in kernel version 3.18. It was improved in version 4.0, bringing improvements necessary for e.g. the overlay2 storage driver in Docker.
The main mechanics of OverlayFS relate to the merging of directory access when both filesystems present a directory for the same name. Otherwise, OverlayFS presents the object, if any, yielded by one or the other, with the "upper" filesystem taking precedence. Unlike some other overlay filesystems, the directory subtrees being merged by OverlayFS do not necessarily have to be from distinct filesystems.
While most of Live CD linux distribution uses Aufs at November 2016, Slackware uses overlayfs for live CD.
OverlayFS supports whiteouts and opaque directories in the upper filesystem to allow file and directory deletion.