Which is the best way to preserve files downloaded by install-tl (e.g. install-tl-20140417) to skip their download the next time install-tl is invoked and told to download from a mirror (this might include invokation with a command line argument, linking directories, etc.)? It would be nice if different versions of packages are preserved (very similar to the apt cache). I don't care about the space used/wasted by old versions on the local system, but about the internet traffic. The download of newest versions of the packages should occur automatically during installation though.
EDIT 2: http://www.tug.org/texlive/doc/install-tl.html doesn't say anything about storage of downloaded binaries. I assume they are moved from /tmp/xzy/ to the installation destination as they are. One option might be using -in-place from the SVN repository.
EDIT 1: Currently the invokation of install-tl with --help is buggy (at least in my case after a failed previous installation). I reported this to tex-live@tug.org (see http://tug.org/pipermail/tex-live/2014-May/035206.html).
retain ...lines) (2) change backup locations to an rsync server (these are thebackup...lines, here fortlnetone would usebackup rsync://your.rsync.ctan.mirror/ctan/systems/texlive/tlnet/ tlnet/- the secondtlnetis the local directory under the backup root as specified insnapshot_root). Hope that helps. – norbert May 23 '14 at 23:59zsyncsupport (see also http://tex.stackexchange.com/questions/184159/is-there-an-overview-list-of-ctan-mirrors-which-support-zsync) the solution might become unpractical for certain users over the time while building from source (https://www.tug.org/texlive/build.html) withTL_MAKE_FLAGS='-j 16'is a valuable alternative to syncing the mirror (might even count as an answer to the question...) – Kalle Richter Jun 10 '14 at 15:58--no-whole-fileoption torsync(but it doesn't come to close tozsyncwith all files in the same directory as input files (might be even extended depending on client resources)) – Kalle Richter Jun 16 '14 at 11:15