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dad02fad84
There are cases where you want to use an overlayfs mount as a lowerdir for another overlayfs mount. For example, if the system rootfs is on overlayfs due to composefs, or to make it volatile (via tmps), then you cannot currently store a lowerdir on the rootfs. This means you can't e.g. store on the rootfs a prepared container image for use using overlayfs. To work around this, we introduce an escapment mechanism for overlayfs xattrs. Whenever the lower/upper dir has a xattr named "overlay.overlay.XYZ", we list it as "overlay.XYZ" in listxattrs, and when the user calls getxattr or setxattr on "overlay.XYZ", we apply to "overlay.overlay.XYZ" in the backing directories. This allows storing any kind of overlay xattrs in a overlayfs mount that can be used as a lowerdir in another mount. It is possible to stack this mechanism multiple times, such that "overlay.overlay.overlay.XYZ" will survive two levels of overlay mounts, however this is not all that useful in practice because of stack depth limitations of overlayfs mounts. Note: These escaped xattrs are copied to upper during copy-up. Signed-off-by: Alexander Larsson <alexl@redhat.com> Reviewed-by: Amir Goldstein <amir73il@gmail.com> Signed-off-by: Amir Goldstein <amir73il@gmail.com> |
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Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.