How to delete lines containing search string using sed

To remove all the lines in a file which has a certain search string can be accomplished easily using sed.

For example, to remove all the lines in in.txt with the text foobar:

$ sed '/foobar/d' in.txt > out.txt

If you would like the line removal to be performed in-place on the input file:

$ sed -i '/foobar/d' in.txt

Tried with: Sed 4.2.2 and Ubuntu 14.04