That error suggests your PATH doesn't include the directory containing the rrdtool program. You have these choices (and probably more):-
1. Add the directory to your PATH. For example:
Code:
export PATH=$PATH:/usr/path/to/rrdtool.dir
2. Specify the full path to the rrdtool program on your command line. For example:
Code:
/usr/path/to/rrdtool.dir/rrdtool ...followed by your options...