You said Linux, so you luck out (at least it should be available, not sure when it was added):
diff --brief -r dir1/ dir2/
If you also want to see differences for files that may not exist in either directory:
diff --brief -Nr dir1/ dir2/
You said Linux, so you luck out (at least it should be available, not sure when it was added):
diff --brief -r dir1/ dir2/
If you also want to see differences for files that may not exist in either directory:
diff --brief -Nr dir1/ dir2/