操作系统原理10章节(733KB).ppt

Example: Mounting iso file under Linux Operating System Concepts mkdir -p /mnt/disk mount -o loop disk1.iso /mnt/disk umount /mnt/disk File Sharing Sharing of files on multi-user systems is desirable. Sharing may be done through a protection scheme. On distributed systems, files may be shared across a network. Network File System (NFS) is a common distributed file-sharing method. Operating System Concepts Protection File owner/creator should be able to control: what can be done by whom Types of access Read Write Execute Append Delete List Operating System Concepts Access Lists and Groups Mode of access: read, write, execute Three classes of users RWX a) owner access 7 ? 1 1 1 b) group access 6 ? 1 1 0 c) public access 1 ? 0 0 1 Ask manager to create a group (unique name), say G, and add some users to the group. For a particular file (say game) or subdirectory, define an appropriate access. Operating System Concepts owner group public chmod 761 game Attach a group to a file chgrp G game A Sample UNIX Directory Listing Operating System Concepts Windows XP Access-control List Management Operating System Concepts Chapter 10: File System Interface 张竞慧 jhzhang@ Chapter 10: File-System Interface File Concept Access Methods Directory Structure File System Mounting File Sharing Protection Operating System Concepts File Concept Contiguous logical address space Types: Data numeric character binary Program Operating System Concepts File Structure None - sequence of words, bytes Simple record structure Lines Fixed length Variable length Complex Structures Formatted document Can simulate last two with first method by inserting appropriate control characters. Who decides? Operating System Concepts File Attributes Name – only information kept in human-readable form. Type – needed for systems that support different types. Location – pointer to file location on device. Size – current file size. Operating System Concepts File Attributes