IDM (INTERNET DOWNLOAD MANAGER ) EQUIVALENT IN UBUNTU : AXEL (TERMINAL BASED DOWNLOAD ACCELERATOR FOR UBUNTU)
Axel is a command-line downloader for unix-like OS .This Program accelerate the downloading process by using multiple connections for one file like IDM in Windows. you can install it by typing sudo aptitude install axel in terminal. Integrate Axel with Mozilla Firefox Using FlashGot add-on. Install FlashGot add-on here .