#!/bin/sh is interpreted inconsistently across platforms. In the rpm
world it most often maps to /bin/bash. In the Debian universe it maps
to /bin/dash. Bash and dash have subtle differences that have bitten
me often enough to cause me now to use precise shebangs (#!/bin/bash or
#!/bin/dash) and to suffix my files with either .bsh or .dsh.
At present emacs' interpreter-mode-alist knows nothing about dash and
its auto-mode-alist is ignorant of both the .bsh and .dsh suffixes.
For interpreter-mode-alist I suggest adding the follow entry:
("dash" . sh-mode)
For auto-mode-alist I suggest changing the follow entry:
("\\.[ck]?sh\\'\\|\\.shar\\'\\|/\\.z?profile\\'" . sh-mode)
("\\.[bcdk]?sh\\'\\|\\.shar\\'\\|/\\.z?profile\\'" . sh-mode)