Solved: extract, creat and etc. tar.xz

tar --xz -xvf filename.tar.xz

Try:

tar xvfJ filename.tar.xz

Note that xz support from tar 1.22 (march 2009). Check your tar version (and upgrade if needed).

I had a tar 1.15.1, which resulted in:

tar: This does not look like a tar archive tar: Skipping to next header tar: Archive contains obsolescent base-64 headers tar: Read 2144 bytes from /path/to/my_archive.tar.xz tar: Error exit delayed from previous errors

With a recent tar, a simple tar xpvf will work (for .tar.xz, or .tar.gz):

tar xpvf /path/to/my_archive.tar.xz -C /path/to/extract

('extract' being the parent directory in which the archive is extracted)