Domain Implementation(域的实现) System consists of2 domains:(系统由2个域构成) User(用户) Supervisor(管理者) ●UNⅨ Domain=user-id(域=用户标识) Domain switch accomplished via file systen.(域变换通过 文件系统完成) Each file has associated with it a domain bit (setuid bit) (每一个文件均和一个域的信息位相联系: setuid位) When file is executed and setuid on. then user-id is set to owner of the file being executed. When execution completes user-id is reset.(当文件被执行并且 setuid 为on,于是用户标识被设置成该文件的属主。当执行完 之后用户标识被重置) Applied Operating System Concepts Silberschatz, Galvin, and Gagne @199918.4 Silberschatz, Galvin, and Gagne ©1999 Applied Operating System Concepts Domain Implementation （域的实现） • System consists of 2 domains:（系统由2个域构成） – User（用户） – Supervisor（管理者） • UNIX – Domain = user-id（域=用户标识） – Domain switch accomplished via file system. （域变换通过 文件系统完成） Each file has associated with it a domain bit (setuid bit). （每一个文件均和一个域的信息位相联系：setuid位） When file is executed and setuid = on, then user-id is set to owner of the file being executed. When execution completes user-id is reset. （当文件被执行并且setuid 为on，于是用户标识被设置成该文件的属主。当执行完 之后用户标识被重置）