I have installed dnvm successfully on windows server 2008. but when I run "dnx", nothing shown. no error message like this:
C:\Windows\system32\dnx
C:\Windows\system32\
someone had the same problem?
First of all you need to understand structure of DNX. By default it's installed in %USERPROFILE%\.dnx. Inside of it you should find runtimes folder containing all of installed CLRs e.g.
Each of them has its own bin folder with dnx.exe and dnu.cmd. These are the ones you are looking for. So basically after executing dnvm upgrade (as suggested by @tugberk) DNVM installs latest DNX from feed, marks it as default and adds it to user's PATH variable. Your PATH might has not been updated for some reason and I suggest you do it manually by including path to your desired CLR version.
It is also possible to install CLR to machine-wide location by adding -g flag.
After try to run: C:\>dnx
Output:
Microsoft .NET Execution environment CLR-x86-1.0.0-beta6-11938
Usage: dnx [options] ...
Detailed documentation on DNVM - ASP.NET Home / Version Manager