rjd at occrsh.UUCP (Randy_Davis) says that if you use ksh as sh, "at" won't work. It works for me. I'm using ksh-i 06/03/86a with System V release 2 (Microport) on an AT clone. ksh is /bin/sh. I've not run into any problems with system software when using ksh as sh. However mine is a single-user system, so I certainly don't see every possible task.