UID/GID shifting filesystem overlays

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One Line Summary

An update on shiftfs and the next steps for remapping overlay filesystems.


Containers using the user namespace have a different view of uid/gid than processes in the initial namespace.

This makes it difficult to share data between the initial namespace and other user namespaces as any unmapped uid/gid will show as -1.

Shiftfs is an overlay filesystem which remaps UIDs and GIDs transparently for you.

This presentation will go over the current state of shiftfs and the next steps needed to get it or something like it merged in the upstream Linux kernel.


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    James E.J. Bottomley

    IBM Research


    James Bottomley is a Distinguished Engineer at IBM Research where he
    works on Cloud and Container technology. He is also Linux Kernel
    maintainer of the SCSI subsystem. He has been a Director on the Board
    of the Linux Foundation and Chair of its Technical Advisory Board. He
    went to university at Cambridge for both his undergraduate and
    doctoral degrees after which he joined AT&T Bell labs to work on
    Distributed Lock Manager technology for clustering. In 2000 he helped
    found SteelEye Technology, a High availability company for Linux and
    Windows, becoming Vice President and CTO. He joined Novell in 2008 as
    a Distinguished Engineer at Novell’s SUSE Labs, Parallels (later Odin)
    in 2011 as CTO of Server Virtualization and IBM Research in 2016.