Hệ điều hành - Chapter 10: Case study 1: Unix and linux

Case Study 1: UNIX and LINUXChapter 1010.1 History of unix 10.2 Overview of unix 10.3 Processes in unix 10.4 Memory management in unix 10.5 Input/output in unix 10.6 The unix file system 10.7 Security in unix 1UNIXThe layers of a UNIX system.UserInterface2UNIX Utility ProgramsA few of the more common UNIX utility programs required by POSIX3UNIX KernelApproximate structure of generic UNIX kernel4Processes in UNIXProcess creation in UNIX.5POSIXThe signals required by POSIX.6System Calls for Process Managements is an error codepid is a process IDresidual is the remaining time from the previous alarm7POSIX ShellA highly simplified shell8Threads in POSIXThe principal POSIX thread calls.9The ls CommandSteps in executing the command ls type to the shell10Flags for Linux cloneBits in the sharing_flags bitmap11UNIX SchedulerThe UNIX scheduler is based on a multilevel queue structure12Booting UNIXThe sequences of processes used to boot some systemscp13Handling MemoryProcess A's virtual address spacePhysical memoryProcess B's virtual address spaceProcess AProcess B14Sharing FilesTwo processes can share a mapped file.A new file mapped simultaneously into two processes 15System Calls for Memory Managements is an error codeb and addr are memory addresseslen is a lengthprot controls protectionflags are miscellaneous bitsfd is a file descriptoroffset is a file offset16Paging in UNIXThe core map in 4BSD.The core map has an entry for each page17Paging in Linux (1)Linux uses three-level page tables18Paging in Linux (2)Operation of the buddy algorithm.Buddy algorithm19NetworkingUse of sockets for networking20Terminal ManagementThe main POSIX calls for managing the terminal21UNIX I/O (1)Some of the fields of a typical cdevsw table22UNIX I/O (2)The UNIX I/O system in BSD23StreamsAn example of streams in System V24The UNIX File System (1)Some important directories found in most UNIX systems25The UNIX File System (2)Before linking.After linking.(a) Before linking. (b) After linking26The UNIX File System (3)Separate file systemsAfter mounting(a)(b)(a) Before mounting. (b) After mounting27Locking Files(a) File with one lock(b) Addition of a second lock(c) A third lock28System Calls for File Managements is an error codefd is a file descriptorposition is a file offset29The lstat System CallFields returned by the lstat system call.30System Calls for Directory Managements is an error codedir identifies a directory streamdirent is a directory entry31UNIX File System (1)Disk layout in classical UNIX systems32UNIX File System (2)Directory entry fields.Structure of the i-node33UNIX File System (3) The relation between the file descriptor table, the open file description34UNIX File System (4)A BSD directory with three filesThe same directory after the file voluminous has been removed35The Linux File SystemLayout of the Linux Ex2 file system.36Network File System (1)Examples of remote mounted file systemsDirectories are shown as squares, files as circles37Network File System (2)The NFS layer structure.The NFS layer structure38Security in UNIXSome examples of file protection modes39System Calls for File Protections is an error codeuid and gid are the UID and GID, respectively40