1. Chapter 6 File Systems CSNB113 SYSTEM ADMINISTRATION
College of Information Technology
Universiti Tenaga Nasional (UNITEN)
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2. Objectives
Understand the initial categorization of files into ordinary, directory and device
Learn the hierarchical structure of file system
Become aware of the significance of absolute and relative pathnames
Understand the four components of file systems
Mount and unmount file systems with mount and unmount
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3. File Container for storing information There types: Ordinary file
Directory file
Device file
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4. Ordinary File The most common file type containing a stream of data
Two types:
Text file
Contains only printable characters
Binary file
Contains both printable and non-printable characters (cover entire ASCII range)
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5. Directory File
Contains no data, but maintains some details of the files and subdirectories that it contains
Each entry has 2 components;
Filename
Unique identification number for the file or directory – inode number
User cannot write directly to the directory file – perform some actions that make the kernel write a directory
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6. Device File
A file that is representing a device that allows the user to perform reading or writing activities from or to the device
Kernel identifies a device from its attributes and then uses them to operate the device.
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7. File System
File system is a logical collection of files on a partition or disk. A partition is a container for information and can span an entire hard drive if desired
File system is organized in the form of a directory structure with its own root
Hard drive can have various partitions which usually contain only one file system, such as one file system housing the /file system or another containing the /home file system
One file system per partition allows for the logical maintenance and management of differing file systems.
Should be kept separately from data files created by users
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8. File System - Unix
Unix uses a hierarchical file system structure, much like an upside-down tree, with root (/) at the base of the file system and all other directories spreading from there.
The directories have specific purposes and generally hold the same types of information for easily locating files.
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9. Partitioning Advantage of partitioning:
Prevent potential violation conflicts between various data areas
Corruption in one area will not affect the others
Perform backup separately
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10. Hierarchy Second Group of File Systems First Group of File Systems /
bin
etc
lib
dev
dsk
fd0
lp0
home
sn010101
sw123456
tmp
usr
sbin
local
var
Second Group of File Systems
First Group of File Systems
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11. / (root) Root file system Swap file system
This is the root directory which should contain only the directories needed at the top level of the file structure
Contains the bare-bones UNIX
Swap file system
Temporary location for processes when memory is heavily loaded – loaded back to memory when swapped processes are ready to run
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12. Hierarchy root directory
top of the hierarchy
Represented by a / (front slash)
Parent is always a directory. An ordinary or device file CANNOT be the parent of another file
Modern UNIX systems – set up with multiple systems – meet specific purpose
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13. UNIX File System
First group – made available during system installation
Directories
Description
/bin and /usr/bin
Store commonly used UNIX commands
/sbin and /usr/bin
Store most of the commands that can only be executed by system administrator
/etc
Configuration files of the system. E.g. /etc/passwd and /etc/shadow
/dev
Contains all device files
/lib and /usr/lib
Contains all library files in binary form
/usr/include
Contains standard header files used by C programs
/usr/share/man
Store manual pages
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14. UNIX File System Second group – files created by the user Directories
Description
/tmp
Allowed to create temporary files – wiped regularly by the system
/var
Part of the file system – print job, incoming or outgoing mail
/home
User’s personal directory
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15. Components of File System
Description
Boot block
Contains a small boot program and the partition table – referred as Master Boot Record (MBR). Boot program – responsible for the eventual loading of kernel into memory
Superblock
Contains global information about the file system. Update disk copy with memory copy
inode blocks
inode (file attributes) for every file of the file system. Keep track of every disk block used by a file
data blocks
All data and program created by users
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16. Absolute Pathnames Using root (/) as the ultimate reference point
Example:
/home/sn010101/dir01/file1.txt
Example of using absolute path name with command:
$ cat /home/sn010101/fileb.txt
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17. Relative Pathnames Pathnames that begin with either of these symbols;
. (a single dot)
Represents CURRENT directory
.. (two dots)
Represents PARENT directory
Example:
$ cd ..
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18. Mounting
A process where all secondary file systems mount (attach) themselves to the root file system
A file system must be mounted in order to be usable by the system.
To see what is currently mounted (available for use) on your system, use the following command −
The /mnt directory, by the Unix convention, is where temporary mounts (such as CDROM drives, remote network drives, and floppy drives) are located.
$ mount
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19. Mounting Use the mount command with the following syntax Example:
This assumes that your CD-ROM device is called /dev/cdrom and that you want to mount it to /mnt/cdrom.
$ mount -t file_system_type device_to_mount directory_to_mount_to
$ mount -t iso9660 /dev/cdrom /mnt/cdrom
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20. Unmounting A process of unmounting the mounted secondary file systems
To unmount (remove) the file system from your system, use the umount command by identifying the mount point or device.
Example: Mount by device name as the argument
The mount command enables you to access your file systems, but on most modern Unix systems, the automount function makes this process invisible to the user and requires no intervention.
$ umount /dev/cdrom
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21. References
Das, S. (2012). Your UNIX/LINUX The Ultimate Guide: Third Edition. McGraw-Hill
Hahn, H. (2008). Harley Hahn's Guide to Unix and Linux. California: McGraw-Hill Higher Education
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