In order for you to play POSTAL on Linux with minimal graphics settings, your computer must meet the following requirements
Operating System:
Ubuntu 12.04 or equivalent
Processor (CPU):
90mhz processor
Memory (RAM):
16 MB RAM
Graphics Card:
No 3D acceleration required
Hard Drive:
400 MB HD space
In order to play POSTAL on Linux with maximum graphics settings, you need a computer with a configuration no worse than the following
Operating System:
Ubuntu 12.04 or equivalent
Processor (CPU):
166mhz processor
Memory (RAM):
32 MB RAM
Graphics Card:
OpenGL 2.0 or later
Hard Drive:
400 MB HD space