dash 0.5.4-1ubuntu3 (amd64 binary) in ubuntu gutsy

 "dash" is a POSIX compliant shell that is much smaller than "bash".
 We take advantage of that by making it the shell on the installation
 root floppy, where space is at a premium.
 .
 It can be usefully installed as /bin/sh (because it executes scripts
 somewhat faster than "bash"), or as the default shell either of root
 or of a second user with a userid of 0 (because it depends on fewer
 libraries, and is therefore less likely to be affected by an upgrade
 problem or a disk failure). It is also useful for checking that a
 script uses only POSIX syntax.
 .
 "bash" is a better shell for most users, since it has some nice
 features absent from "dash", and is a required part of the system.