Dash

dash is the Debian Almquist shell: Article description::a small, fast, and POSIX compliant [[shell.]] It is well-suited for startup scripts, and used on Debian (and derivative distributions) as replacement. As some shell scripts may have bashisms in them, it is not guaranteed to work out-of-the-box on Gentoo as replacement.

Configuration
Make dash the default system shell:

Use dash as current shell: