Yesterday when I was trying to update the OpenCV in my BBB, a strange thing happened. After downloading and unzipping OpenCV 2.4.9 in BBB , I couldn't log into my BBB via ssh (but using the webpage still worked). The terminal responded nothing, and it just hanged there without logging in.
I searched and tested, the first script given in the mail list  didn't work to me. It returned ``it seems that you have another problem, sorry.''
Then I tested the second script . After running that script I logged in BBB via ssh again.
Actually I still have no idea what'd happened. Maybe the resource of BBB had been run out after the downloading of OpenCV? Maybe something else caused the problem.
I read the mail list again and found the post which listed the second script had said something may be useful. It talked about systemd-journal settings.
 I wouldn't do it again. At the beginning, I was planning to build OpenCV 2.4.9 in my BBB. Later, I read VAT's article and knew that I should use cross-compilation.
 The script:
 The script worked for me: