File Systme
A 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.
Your 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.
About Unix Filesystems: Moments from History
In the beginning was the System V filesystem. Well, not really, but that’s where we’ll
start. This filesystem type once dominated System V–based operating systems.*
The superblock of standard System V filesystems contained information about cur-
rently available free space in the filesystem in addition to information about how the
space in the filesystem is allocated. It held the number of free inodes and data blocks,
the first 50 free inode numbers, and the addresses of the first 100 free disk blocks.
After the superblock came the inodes, followed by the data blocks.
Administering a filesystem
includes tasks such as:
• Making local and remote files available to users
• Monitoring and managing the system’s disk resources
• Protecting against file corruption, hardware failures, and user errors via a well-
planned backup schedule
• Ensuring data confidentiality by limiting file and system access
• Checking for and correcting filesystem corruption
• Connecting and configuring new storage devices when needed
Filesystem Types
Default Local Filesystems
Managing Filesystems
Mounting and Dismounting Filesystems
Disk Special File Naming Conventions
filesystem configuration file
checking local filesystem integrity with the fsck utility
Directory Structure
Unix uses a hierarchical file system structure, much like an upside-down tree, with root (/) at the base of the file system
A Unix filesystem is a collection of files and directories that has the following properties −
It has a root directory (/) that contains other files and directories.
Each file or directory is uniquely identified by its name, the directory in which it resides, and a unique identifier, typically called an inode.
By convention, the root directory has an inode number of 2 and the lost+found directory has an inode number of 3. Inode numbers 0 and 1 are not used. File inode numbers can be seen by specifying the -i option to ls command.
It is self-contained. There are no dependencies between one filesystem and another.
The directories have specific purposes and generally hold the same types of information for easily locating files. Following are the directories that exist on the major versions of Unix −
| Sr.No. | Directory & Description |
|---|---|
| 1 | / This is the root directory which should contain only the directories needed at the top level of the file structure |
| 2 | /bin This is where the executable files are located. These files are available to all users |
| 3 | /dev These are device drivers |
| 4 | /etc Supervisor directory commands, configuration files, disk configuration files, valid user lists, groups, ethernet, hosts, where to send critical messages |
| 5 | /lib Contains shared library files and sometimes other kernel-related files |
| 6 | /boot Contains files for booting the system |
| 7 | /home Contains the home directory for users and other accounts |
| 8 | /mnt Used to mount other temporary file systems, such as cdrom and floppy for the CD-ROM drive and floppy diskette drive, respectively |
| 9 | /proc Contains all processes marked as a file by process number or other information that is dynamic to the system |
| 10 | /tmp Holds temporary files used between system boots |
| 11 | /usr Used for miscellaneous purposes, and can be used by many users. Includes administrative commands, shared files, library files, and others |
| 12 | /var Typically contains variable-length files such as log and print files and any other type of file that may contain a variable amount of data |
| 13 | /sbin Contains binary (executable) files, usually for system administration. For example, fdisk and ifconfig utlities |
| 14 | /kernel Contains kernel files |
Navigating the File System
Now that you understand the basics of the file system, you can begin navigating to the files you need. The following commands are used to navigate the system
| Sr.No. | Command & Description |
|---|---|
| 1 | cat filename Displays a filename |
| 2 | cd dirname Moves you to the identified directory |
| 3 | cp file1 file2 Copies one file/directory to the specified location |
| 4 | file filename Identifies the file type (binary, text, etc) |
| 5 | find filename dir Finds a file/directory |
| 6 | head filename Shows the beginning of a file |
| 7 | less filename Browses through a file from the end or the beginning |
| 8 | ls dirname Shows the contents of the directory specified |
| 9 | mkdir dirname Creates the specified directory |
| 10 | more filename Browses through a file from the beginning to the end |
| 11 | mv file1 file2 Moves the location of, or renames a file/directory |
| 12 | pwd Shows the current directory the user is in |
| 13 | rm filename Removes a file |
| 14 | rmdir dirname Removes a directory |
| 15 | tail filename Shows the end of a file |
| 16 | touch filename Creates a blank file or modifies an existing file or its attributes |
| 17 | whereis filename Shows the location of a file |
| 18 | which filename Shows the location of a file if it is in your PATH |
