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The current DIB element support for downloading tarballs via "source-repository" allows an entry in the following form:

<name> tar <targetdir> <url>

Today, this feature is currently used only by the mysql DIB element. You can see how it's used here:
https://github.com/openstack/tripleo-image-elements/blob/master/elements/mysql/source-repository-mysql

However, the underlying diskimage-builder implementation of tarball handling is rather odd and inflexible. After downloading the file (or retrieving from cache) and unpacking into a tmp directory, it performs:

mv $tmp/*/* $targetdir

This does work as long as the tarball follows a structure where all its files/directories are contained within a single directory, but it fails if the tarball contains no subdirectories. (Even worse is when it contains some files and some subdirectories, in which case the files are lost and the contents of all subdirs get lumped together in the output folder.)

Since this tarball support is only used today by the mysql DIB element, I would love to fix this in both diskimage-builder and tripleo-image-element by changing to simply:

mv $tmp/* $targetdir

And then manually tweaking the directory structure of $targetdir from a new install.d script in the mysql element to restore the desired layout.

However, it's important to note that this will break backwards compatibility if tarball support is used in its current fashion by users with private DIB elements.

Personally, I consider the current behavior so egregious that it really needs to be fixed across the board rather than preserving backwards compatibility.

Do others agree? If not, do you have suggestions as to how to improve this mechanism cleanly without sacrificing backwards compatibility?

Thanks,

Jonathan