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File-System Inteface (File Concept (Attributes (Name, Identifier, Type,…
File-System Inteface
File Concept
Computers can store information on various storage media, such as magnetic disks, magnetic tapes, and optical disks.
The operating system abstracts from the physical
properties of its storage devices to define a logical storage unit called the file.
Attributes
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Time, date, and user identification
Access Methods
Sequential Access
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Information in the file is
processed in order, one record after the other.
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Direct Access
Can also be called relative access. A file is made up of fixed length logical records that allow programs to read and write records rapidly with no specific order.
The direct-access method is based on a disk
model of a file, since disks allow random access to any file block.
Other Methods
These methods generally involve the construction of an index for the file. The index, like an index in the back of a book, contains pointers to the various blocks.
IBM’s indexed sequential-access method (ISAM) uses a small
master index that points to disk blocks of a secondary index.
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Protection
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Access Control
The general way is to implement identity access is to associate with each file and directory an access-control list specifying user names and permissions for each user type.
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File-System Mounting
The mount procedure is straightforward. The operating system is given the name of the device and the mount point where the file system will be attached.
The OS verifies that the device contains a valid file system. It does so by asking the device driver to read the device directory and verifying that the directory has the expected format.
File Sharing
Multiple Users
The issues of file sharing, file naming, and file protection become preeminent.
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Remote File Systems
The first implemented method involves manually transferring files between machines via programs like ftp.
The second major method uses a distributed file system (DFS) in which remote directories are visible from a local machine.
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TEC, Sede Central Cartago, Escuela de Computacion, Sistemas Operativos
Reporte #11 - Operating System Concepts - Capitulo 11 - File-System Interface Guilliano Dambrosio Soza, 2017158561 13/10/2019, II Semestre, Esteban Arias