Sistemas operativos

OPERATING SYSTEMS II


AUTHOR: JOSE CARLOS CASTAÑO GRACIA

Jose Carlos Castaño Gracia 1 OPERATING SYSTEMS II

Contents

FILE SYSTEM Files File naming File Structure File Types File Access File Attributes File Operations Memory-mapped Files Directories Single-levels directory systems Two-levels directory systems Hierarchical directory systems Path names Directory Operations File Systemimplementation File system layout Implementing Files Implementing Directories Shared Files Disk space management File system reliability File system performance Log-structured File systems MULTIMEDIA OPERATING SYSTEMS Multimedia files Audio encoding Video encoding Video compression The JPEG standard The MPEG standard Multimedia process scheduling Scheduling homogeneous processes General real-timescheduling Rate monotonic scheduling Earliest deadline first scheduling

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Jose Carlos Castaño Gracia 2 OPERATING SYSTEMS II

MULTIPLE PROCESSOR SYSTEMS Multiprocessors Multiprocessor hardware Multiprocessor operating system types Multiprocessor synchronization Multiprocessor scheduling Multicomputers Multicomputer hardware Low-level communication softwareUser-level communication software Remote procedure call Distributed shared memory Multicomputer scheduling Load balancing Distributed systems Network hardware Network services and protocols Documents-based middleware File-system-based middleware Shared object-based middleware Coordination-based middleware SECURITY Threats User authentication Authentication using password Authentication using aphysical object Authentication using biometrics Countermeasures Attacks Attacks from inside the system Attacks from outside the system Protection mechanisms Protection domains Access control lists Capabilities

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Jose Carlos Castaño Gracia 3 OPERATING SYSTEMS II

1. FILE SYSTEM. To store the information of permanent form, it will be necessary threebasic requirements: Aptitude to store a lot information The information must remain when the process expires Multiple processes acceding to the information

The solution to these requirements is to use external means to store the information as “files”. The way of managing the files will depend on the Operating System. 1.1. FILES 1.1.1. FILE NAMING When a process creates a file, it will assign aname, across which it will be possible accede to in the future, enclosed if the process finished. The rules to name files change from a system to other one, it common that they are chains of 8 letters, also we can use special characters. There exist systems that they recognize up to 255 characters of length. Several systems of files exist, it depends on the system there will be distinction betweencapital letters (UNIX) or not (MSDOS). We can find name of files with extension, this type of names will be for example file1.txt or file2.c. Some systems were limiting his use for the assigned extension, but in others the extension only will serve to help the user. 1.1.2. FILE STRUCTURE We will be able to be different ways of structuring the files, the common three are: Sequences of Bytesdesestructuradas. The operating system does not know that it contains the file, it will be the program (user's level) the one that takes charge giving sense. Succession of records of length fixes. The operation of reading will return a record, as well as the operation of writing overwrites or adds a record. Tree of records. Not all the records will be of the same length, every tree will have a key fieldin a fixed position of the record. We will be able to find a key with facility. 1.1.3. FILE TYPES

Jose Carlos Castaño Gracia 4 OPERATING SYSTEMS II

We can find some types of Files as “Regular files”, “Character special files” or “Block special files”, we are going to speak in this section about “Regular files”. This file types contain user information and they are generally either ASCII...