Debian and Ubuntu switched to dash (iirc) because of a couple of things. First of all, Bash has become big over the years. In fact, the /bin/bash binary on my Ubuntu 8.04 system is almost ten times (!) as big as /bin/dash . Now, that does not matter much for day to day shell use, but it does matter in the following situations: Dash is much smaller and thus loads faster, which is a boon for init-scripts. If you have to start a lot of them, loading Dash instead of Bash each time, speeds things up considerably. Because of the smaller size of Dash, Debian and Ubuntu are able to shave off a pretty big chunk of the size of their initrd, leaving more room for other stuff (and again, speeding things up). The downside of using Dash instead of Bash for scripting, is that a lot of people use syntactical niceties only Bash has, the so-called Bashisms . Examples of Bashisms are substrings, like this: echo $SHELL / bin / bash a = 1234567890 echo $ { a } 1234567890 ...