File System Study Guide

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File system Concept A file is collection of related information recorded on secondary storage by sequence of bits, bytes, lines or records. All data written to secondary storage in file format, which can be numeric, alphabetic, alphanumeric or binary. Attributes of files: - name to which system refers when file participates in process; - file identifier; - file type ( text, source, object, executable); - location; - size; - protection level; - creation / modification date. Operations with files: - creating: defining file place in the system and creating directory entry; - writing: specifying file name and information which file will contain; - reading; - repositioning within file; - deleting: releasing both file space and directory entry; - truncating: erasing file content. File access - sequential access: file record is read one after another; - direct access: file allows random access to any block; - indexed access: search is done through file index. Directories As files can be different in sizes and types, they need tp be organised. Then each storage volume contains information about files in this storage-volume table of contents. By complexity of structure following directories types defined: - Single level: all file are on the same level and all files have unique names; - Two level: each user has own file directory …show more content…

Users are allowed to view all file under single directory, not even knowing under which particular file system it is stored. Location of each file, directory or link is described by object called inode. Inode is unique to particular file system and does not include name, which is allows creating multiple hard links that map several file names to the same inode. Each file is represented by file descriptor. VFS uses Dentry (Directory Entry) to map file using inode and file names. For each file name there is pointer to corresponding inode. Thus, the system resolves pathname-inode conversion

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