What is the Glibc Iconv Encodings _iconv_from Feature

[berney]

I see that in the kubler/glibc image that it makes a tarball backup of the Glibc Iconv encodings and mentions users can get them with _iconv_from.
I see in kubler that if _iconv_from is set it will add a footer to the documentation.
But I don't see any helper function or similar that will extract the tarball.

I'm curious how this feature works, if I misunderstand the code, or if a piece is missing or got renamed.

[edannenberg]

That's an internal generic feature called build_dependencies, which covers edge cases where some resources like header files that only exist in the final rootfs tar ball are stored in the image dir as a separate tar ball. Child images that might need these files at build time can pull them in again via this mechanism.

Searching for headers_from in the kubler-images repo should give better insight on how it is used.

But I don't see any helper function or similar that will extract the tarball.

See extract_build_dependencies() and build_rootfs().

[r7l]

Just stumbled across this as i've had an application unable to run without iconv. Took me a while to realize what's going on but this feature is actually nice.