My advisor's new student copied parts of my PhD thesis; advisor doesn't care. What to do? I wrote my PhD thesis a few years back. After I finished, my supervisor found another researcher and continued research with the apparatus I built, but along a different line of study. I met this student a few times and gave them advice and help when I could. They always had a hard copy of my thesis in the lab for reference; I also provided a PDF copy at the student's request. 

The student recently finished their PhD and I looked at their thesis. The lit review, results, and findings are the student's own work. But, particularly in the middle section (describing the apparatus I built): 


Many paragraphs of their text is copied and pasted from mine, some without checking so that it makes false references;
In other instances, the student has substantially copied paragraphs, but changed a few words here and there;
One that particularly annoyed me was the copying and awkward re-hashing of my acknowledgements to my supervisor, very personal words; 


I informed my former supervisor (with whom I have a good relationship) and he seemed not to want to know. He said that as long as it wasn't the results then it wasn't too important. He reckoned as the student was a good guy, he may not have known what plagiarism was, and perhaps did it by accident. He did offer to acknowledge or include me in subsequent journal papers.

Given that only some of the background text (rather than the results section) was copied, is it reasonable to pursue this further? What is normally done in such cases?

In particular, I was thinking to quantify the level of copying involved and ask my supervisor to withdraw the thesis until copied material is removed. However, I risk jeopardizing a fairly good relationship with my supervisor and possibly also with the small network of colleagues.
You have two options:


Not care about plagiarism enough to warrant getting involved. 
Care about plagiarism to the degree you get involved.


There are arguments for both points here. 


It would be an obvious matter of record as to whose thesis was written first if anyone else happened to notice the similarities. Why get involved further? You notified the adviser, let him deal with blowback from letting a student plagiarize. Pushing the issue further would just compromise your relationship with your adviser. Whistleblowers rarely get rewarded properly anyway. And, cynically, some universities may not even care about a student plagiarizing parts of a thesis. It's more paperwork and labor for them to deal with and it's easier to just hope (from an administrative perspective) that the problem goes away.
Based on what you have told us, it seems reasonable that your thesis was plagiarized from. You have contacted the adviser about this and he declined to do much about it. The graduate college and university administration, however, may not concur with your adviser. Plagiarism should be stopped on principle alone. I would report the offending thesis to the graduate college and see if they are willing to investigate it further. If you really wanted to do some nasty damage and the university declines to investigate, notify the local newspaper and see if they'll send over some junior journalist to write a spot on how your university is allowing plagiarism to occur. 


Part of writing a thesis is learning to articulate in your own words what your research is about. This has to do with much more than just shoving original data in a table.   

If your adviser told you the student "might not know what plagiarism is" then.....wow.....No one reaches graduate school and is completely oblivious to what plagiarism is. Let's be honest here. 

For me personally, I would let it go. The network with my adviser is more important to my career right now. This is pragmatism, not principle, speaking.