Q:

V-Modell XT installer: "installation failed" error / missing proxy settings and how to provide them

downloadable from here: http://www.cio.bund.de/DE/Architekturen-und-Standards/V-Modell-XT/vmodell_xt_node.html
nothing is written to the log (they are empty ... in tmp folder or installation folder if existing) and no further details are given.

A:

problem for my environment were missing http proxy settings.
Solved via providing them via system properties (https.proxy* variables are auto-set to the same values): 
-Dhttp.proxyHost=<your-proxy-host>
-Dhttp.proxyPort=<your-proxy-port>
-Dno_proxy=<some-internal-ip1>;<some-internal-ip-range.*>;<some-dns-name-pattern, e.g. '*.mycomp.*'>

an even nicer way to provide such proxy settings is by using some system environment variable named JAVA_TOOLS_OPTIONS which applies these proxies by default to all kinds of your Java executables by default since JRE 1.7:
http://docs.oracle.com/javase/7/docs/webnotes/tsg/TSG-VM/html/envvars.html
also discussed and answered here: https://stackoverflow.com/a/12723083/1915920
e.g. in Windows just set it up under
-> Start Menu 
-> type: "environment variables ..." and click on the right app
-> add as system or user variable

