OverlayFS is a union mountfilesystem implementation for Linux. It combines multiple different underlying mount points into one, resulting in single directory structure that contains underlying files and sub-directories from all sources. Common applications overlay a read/write partition over a read-only partition, such as with LiveCDs and IoT devices with limited flash memory write cycles.
The need and specification of a kernel mode Linux union mount filesystem was identified in late 2009.[1] The initial RFC patchset of OverlayFS was submitted by Miklos Szeredi in 2010.[2] By 2011, OpenWrt had already adopted it for their use.[3]
It was merged into the Linux kernel mainline in 2014, in kernel version 3.18.[4][5] It was improved in version 4.0, bringing improvements necessary for e.g. the overlay2 storage driver in Docker.[6]
While most Live CD linux distributions used Aufs as of November 2016, Slackware used overlayfs for its live CD.[7]
Implementationedit
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.[8]
OverlayFS supports whiteouts and opaque directories in the upper filesystem to allow file and directory deletion.[8]
OverlayFS does not support renaming files without performing a full copy-up of the file; however, renaming directories in an upper filesystem has limited support.
OverlayFS does not support merging changes from an upper filesystem to a lower filesystem.
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overlayfs, union, mount, filesystem, implementation, linux, combines, multiple, different, underlying, mount, points, into, resulting, single, directory, structure, that, contains, underlying, files, directories, from, sources, common, applications, overlay, r. OverlayFS is a union mount filesystem implementation for Linux It combines multiple different underlying mount points into one resulting in single directory structure that contains underlying files and sub directories from all sources Common applications overlay a read write partition over a read only partition such as with LiveCDs and IoT devices with limited flash memory write cycles OverlayFSDeveloper s Miklos Szeredi Open Source CommunityFull nameOverlay File SystemFeaturesFile systempermissionsPOSIXOtherSupportedoperating systemsLinux FreeBSD and NetBSD Contents 1 History 2 Implementation 3 See also 4 References 5 External linksHistory editThe need and specification of a kernel mode Linux union mount filesystem was identified in late 2009 1 The initial RFC patchset of OverlayFS was submitted by Miklos Szeredi in 2010 2 By 2011 OpenWrt had already adopted it for their use 3 It was merged into the Linux kernel mainline in 2014 in kernel version 3 18 4 5 It was improved in version 4 0 bringing improvements necessary for e g the overlay2 storage driver in Docker 6 While most Live CD linux distributions used Aufs as of November 2016 Slackware used overlayfs for its live CD 7 Implementation editThe 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 8 OverlayFS supports whiteouts and opaque directories in the upper filesystem to allow file and directory deletion 8 OverlayFS does not support renaming files without performing a full copy up of the file however renaming directories in an upper filesystem has limited support OverlayFS does not support merging changes from an upper filesystem to a lower filesystem See also editAufs UnionFS an older union mount projectReferences edit Aurora Valerie March 18 2009 Unioning file systems Architecture features and design choices LWN net Retrieved 2018 01 17 Edge Jake September 1 2010 Another union filesystem approach LWN net Retrieved 2018 01 17 Corbet Jonathan June 15 2011 Debating overlayfs LWN net Retrieved 2018 01 17 OverlayFS commit to Linux GitHub OverlayFS Proposed For The Linux 3 18 Kernel Select a storage driver Docker archive is 2016 12 06 Archived from the original on 2016 12 06 Retrieved 2017 06 05 a href Template Cite news html title Template Cite news cite news a CS1 maint bot original URL status unknown link slackware liveslak SlackDocs docs slackware com Retrieved 2017 06 05 a b OverlayFS documentation kernel org External links editOverlayFS documentation Retrieved from https en wikipedia org w index php title OverlayFS amp oldid 1220143517, wikipedia, wiki, book, books, library,
