special permissions within Red Hat Linux.
- setuid — used only for applications, this permission indicates that the application runs as the owner of the file and not as the user executing the application. It is indicated by the character s in place of the x in the owner category. If the owner of the file does not have execution permissions, the S is capitalized.
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setgid — used primarily for applications, this permission indicates that the application runs as the group owning the file and not as the group executing the application. If applied to a directory, all files a user creates within the directory are owned by the group who owns the directory, rather than by the user's private group (see the chapter titled Users and Groups in Official Red Hat Linux Reference Guide for more about user private groups). It is indicated by the character s in place of the x in the group category. If the group owner of the file or directory does not have execution permissions, the S is capitalized.
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sticky bit — used primarily on directories, this bit dictates that a file created in the directory can be removed only by the user who created the file. it is indicated by the character t in place of the x in the everyone category. in Red Hat Linux the sticky bit is set by default on the /tmp/ directory for exactly this reason.
