dash software package provides POSIX-compliant shell, you can install in your Debian 7 (Wheezy) by running the commands given below on the terminal,
$ sudo apt-get update $ sudo apt-get install dash
dash is installed in your system.
Make ensure the dash package were installed using the commands given below,
$ sudo dpkg-query -l | grep dash *
You will get with dash package name, version, architecture and description in a table
| Distro | Debian 7 wheezy |
| Section | Shells |
| Package | dash |
| Version | 0.5.7-3 |
| Description | POSIX-compliant shell |
| Sub Section | Shells |