Skip to main content

File permissions

Linux permissions are basically split into two areas.
These are:
• File ownership
• File access permissions
Every file has an owner. This is usually the user who created the file, although this can be changed.Users can also be classed into groups, so similar users can be grouped together.
The other element is the access permissions for the file. These are split into three areas:
• Who can read (view) the file ( r)
• Who can write to the file (w)
• Who can run the file (this only applies to files that can be run) (x)
Let’s look an example. Open a console and do a directory listing by typing:
ls -al
at the command line.
 This is simply a directory listing, but lets look at one line as an example:
-rw-r r   1   jono    jono    1701    Jul 13 15:23   test.txt
A lot of information is given. Reading the information from left to right, this is what it means:
-           File type indicator (- means normal file)
rw-r r File permissions
jono   Owner
jono   Group
1701 File size
Jul 12 15:23 File creation time and date
test.txt Filename

Setting File Permissions

To change the permissions on a file we use the chmod command, which has the format:
chmod   filename(s)
The chmod command is a very versatile command and can change the permissions in a number of ways. Probably the easiest way to remember is by changing the permissions using the same letters to set them as they are displayed (r, w and x or octal digits 4 2 1). To do this you must first specify the section that you want to change (owner (u), group (g) or other (o)). You must then specify + or - to indicate whether you are giving (+) permissions or removing (-) them. Suppose that you would like to change the file test.txt so that all other users on the system can read and write to it. You would use:
chmod o+rw   test.txt

This command basically says give every other user on the system (o) addition permissions (+) that are read (r) and write (w) on the file nickmail.txt.
Same can be written using octal form as

chmod 006   test.txt    this is absolute assignment which will remove other permissions
Labels:

Comments

Post a Comment

Popular posts from this blog

Writing a Bash Shell Script

Bash shell scripts in Linux are text files that contain a series of commands that can be executed by the Bash shell. Bash (Bourne Again Shell) is a popular shell in Linux and UNIX systems, and shell scripts are used to automate tasks, configure systems, or perform a sequence of operations. How to Write a Bash Shell Script Create a New File: You can create a new script using any text editor like nano , vim , or gedit . gedit myscript.sh Write the Script: A basic shell script begins with a "shebang" ( #!/bin/bash ) to specify the interpreter that will be used to execute the script. The rest of the file contains the commands to be run. Example of a simple script: #!/bin/bash # This is a comment echo "Hello, World!" # Print "Hello, World!" #!/bin/bash : Specifies that the script will be executed using the Bash shell. echo "Hello, World!" : A command that prints the string "Hello, World!" to the terminal. Comments: Any line starting ...
Post a Comment
Read more

Basic Linux Commands For Beginner's

Basic Linux Commands for Beginners Linux is an Operating System’s Kernel. You might have heard of UNIX. Well, Linux is a UNIX clone. But it was actually created by Linus Torvalds from Scratch. Linux is free and open-source, that means that you can simply change anything in Linux and redistribute it in your own name! There are several Linux Distributions, commonly called “distros”. A few of them are: Mint Ubuntu Linux Red Hat Enterprise Linux Debian Fedora Kali Linux is Mainly used in Servers. About 90% of the Internet is powered by Linux Servers. This is because Linux is fast, secure, and free! The main problem of using Windows Servers are their cost. This is solved by using Linux Servers. Forgot to mention, the OS that runs in about 80% of the Smartphones in the World, Android, is also made from the Linux Kernel. Yes, Linux is amazing! A simple example of its security is that most of the viruses in the world run on Windows, but not on Linux...
4 comments
Read more

Linux History and GNU

Linus Torvalds ,a student at the University of Helsinki started developing Linux to create a system similar to MINIX, a UNIX operating system. In 1991 he released version 0.02; Version 1.0 of the Linux kernel, the core of the operating system, was released in 1994. About the same time, American software developer Richard Stallman and the FSF made efforts to create an open-source UNIX-like operating system called GNU. In contrast to Torvalds, Stallman and the FSF started by creating utilities for the operating system first. These utilities were then added to the Linux kernel to create a complete system called GNU/Linux, or, less precisely, just Linux. Linus Torvalds Richard Stallman Linux grew throughout the 1990s because of the efforts of hobbyist developers. Although Linux is not as user-friendly as the popular Microsoft Windows and Mac OS operating systems, it is an efficient and reliable system that rarely crashes. Combined with Apache, an open-source Web server, Linux accounts fo...
Post a Comment
Read more