File Management and Simple commands in Unix class 3. Please watch: "How to use CONCATENATE function in MS EXCEL: Excel Tutorial"
File Management and Simple commands in Unix
Internal Structure Of The File System
In the UNIX system, every file has a table associated with it, which is stored in a special area of the disk, which is known as identification node (i-node). The i-node describes the file uniquely.
Every file system consists of a sequence of blocks, each block consisting of 512 bytes. Some of these blocks are not allotted to the user, and are reserved exclusively for the use of the kernel. The file system breaks the disk in to four segments as follows
1. The Boot Block
The first block, numbered 0, is called the boot block, which is normally unused by the file system, and set aside for the booting procedure. This is true for the main file system. For the other file systems, this is left unused.
2. The Super Block
This is the block numbered 1, and is used to control the allocation of disk blocks. This contains the details of the active file system, like the size of the file system, the details of the free blocks and I-nodes
To communicate with your computer you will require:
a terminal with a full American Standard Code for Information Interchange (ASCII) character set a data communication line to the computer
a login ID
A terminal session begins by logging in through a recognized terminal and ends by logging off. The computer will do work for you in response to the commands that you enter during your terminal session.
The UNIX system identifies the many users on the system by their user name (sometimes called the login ID). Your login, which is assigned to you by your system administrator, is normally your name or initials. A password may optionally be assigned to your account. If you forget your password, you will have to ask your system administrator for assistance. Only the system administrator has the authority to delete a user's password from his or her account.
login : kumar
If a password has been allotted to you, the system will flash the following message.
The password will not be echoed on the screen. If you enter an incorrect password or login name it will display the message
You will be permitted to reenter your password a fixed number of times before you get it right.
If your login information is right, it will display a welcome message, Terminal type and then show you the $ prompt
Terminal type is ansi
When you have finished, you terminate your terminal session by logging off. This frees up the terminal so that another user can log in. It is also recommended that you log off when leaving your terminal unattended to prohibit others from accessing your terminal session and user account
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