lsof software package provides Utility to list open files, you can install in your Ubuntu 14.04 LTS (Trusty Tahr) by running the commands given below on the terminal,
$ sudo apt-get update $ sudo apt-get install lsof
lsof is installed in your system.
Make ensure the lsof package were installed using the commands given below,
$ sudo dpkg-query -l | grep lsof *
You will get with lsof package name, version, architecture and description in a table
| Distro | Ubuntu 14 04 lts trusty tahr |
| Section | Utilities |
| Package | lsof |
| Version | 4.86+dfsg-1ubuntu2 |
| Description | Utility to list open files |
| Sub Section | Utils |