上海交通大学：《操作系统 Operating System》课程教学资源（课件讲稿）OS-Lec22_file system implementation

REVIEW o Allocation of Frames o Thrashing o Working-Set Model o Copy-on-Write o Memory-Mapped Files o Other Consideration ·Prepaging ·Page Size

REVIEW  Allocation of Frames  Thrashing  Working-Set Model  Copy-on-Write  Memory-Mapped Files  Other Consideration  Prepaging  Page Size 1

CHAPTER 10:FILE-SYSTEM INTERFACE o File Concept o Access Methods o Directory Structure o File-System Mounting o File Sharing o Protection

CHAPTER 10: FILE-SYSTEM INTERFACE  File Concept  Access Methods  Directory Structure  File-System Mounting  File Sharing  Protection

Symbolic Open Levels of file name file ID abstraction USER File system interface Files/ directories Directory High-level file and FS management directory functions Logical block Basic file IO system Open/close functions Physical device address Device organization Low-level data methods access functions IO system interface Logical block#

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PROTECTION o File owner/creator should be able to control: ·what can be done ·by whom o Types of access ·Read ·Write 。Execute ·Append ·Delete ·List

PROTECTION  File owner/creator should be able to control:  what can be done  by whom  Types of access  Read  Write  Execute  Append  Delete  List

ACCESS LISTS AND GROUPS o Mode of access:read,write,execute o Three classes of users RWX a)owner access 7 → 111 RWX b) group access 6 → 110 RWX c)public access 1 → 001 o Ask manager to create a group (unique name),say G,and add some users to the group. o For a particular file (say game)or subdirectory,define an appropriate access. owner group public chmod 761 game Attach a group to a file chgrp G game

ACCESS LISTS AND GROUPS  Mode of access: read, write, execute  Three classes of users RWX a) owner access 7  1 1 1 RWX b) group access 6  1 1 0 RWX 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. owner group public chmod 761 game Attach a group to a file chgrp G game

WINDOWS XP ACCESS-CONTROL LIST MANAGEMENT 10.tex Properties ?× General Security Summary Group or user names: Administrators (PBG-LAPTOPAdministrators) 五Guest(P日G出LAPTOPGues黄 pbg (CTKpbg) 经SYSTEM Users (PBG-LAPTORUsers) Add... Remove Permissions for Guest Allow Deny Full Control □ ☑ Modify Pga.d&Execut日 Read 口 Write ☑ Special Permissions For special permissions or for advanced settings. Advvanced click Advanced. OK Cancel Apply

WINDOWS XP ACCESS-CONTROL LIST MANAGEMENT

A SAMPLE UNIX DIRECTORY LISTING -rW-rW-r-- 1 pbg staff 31200 Sep308:30 intro.ps drwx------ 5 pbg staff 512 Jul809.33 private/ drwxrwxr-X 2pbg staff 512 Jul809:35 doc/ drwxrwx--- 2 pbg student 512 Aug314:13 student-proj W--I-- 1 pbg staff 9423 Feb242003 program.c rwxr-xr-X 1pbg staff 20471 Feb242003 program drwx--X--X 4 pbg faculty 512 Jul3110:31 lib/ drwx------ 3 pbg staff 1024 Aug2906:52 mail/ drwxrwxrwx 3 pbg staff 512 Jul809:35 test/

A SAMPLE UNIX DIRECTORY LISTING

CHAPTER 11:FILE SYSTEM IMPLEMENTATION

CHAPTER 11: FILE SYSTEM IMPLEMENTATION

CHAPTER 11:FILE SYSTEM IMPLEMENTATION o File-System Structure o File-System Implementation o Directory Implementation o Allocation Methods o Free-Space Management 9

CHAPTER 11: FILE SYSTEM IMPLEMENTATION  File-System Structure  File-System Implementation  Directory Implementation  Allocation Methods  Free-Space Management 9

FILE-SYSTEM STRUCTURE o File structure ·Logical storage unit Collection of related information o File system resides on secondary storage (disks) o File system organized into layers o File control block-storage structure consisting of information about a file

FILE-SYSTEM STRUCTURE  File structure  Logical storage unit  Collection of related information  File system resides on secondary storage (disks)  File system organized into layers  File control block – storage structure consisting of information about a file