Grant the System Group Read & Execute Permissions for the Installer

Linux is a clone of UNIX, the multi-user operating system which can be accessed past many users simultaneously. Linux can also be used in mainframes and servers without any modifications. Just this raises security concerns as an unsolicited or malign user tin can corrupt, change or remove crucial data. For effective security, Linux divides say-so into 2 levels.

1. Ownership
2. Permission

In this Linux file commands tutorial, you volition learn-

• Linux File Ownership
• Linux File Permissions
• Changing file/directory permissions in Linux Using 'chmod' command
• Absolute(Numeric) Way in Linux
• Symbolic Fashion in Linux
• Changing Ownership and Group in Linux

The concept of Linux File permission and ownership is crucial in Linux. Hither, we will explain Linux permissions and ownership and will discuss both of them. Let u.s.a. commencement with the Ownership.

Click here if the video is non attainable

Linux File Ownership

Every file and directory on your Unix/Linux organization is assigned 3 types of owner, given below.

User

A user is the owner of the file. Past default, the person who created a file becomes its owner. Hence, a user is as well sometimes chosen an owner.

Grouping

A user- grouping tin contain multiple users. All users belonging to a group will take the same Linux group permissions access to the file. Suppose you accept a project where a number of people require access to a file. Instead of manually assigning permissions to each user, you could add all users to a group, and assign grouping permission to file such that only this group members and no i else can read or modify the files.

Other

Whatever other user who has access to a file. This person has neither created the file, nor he belongs to a usergroup who could own the file. Practically, it means everybody else. Hence, when you set the permission for others, it is also referred every bit set permissions for the globe.

At present, the big question arises how does Linux distinguish between these iii user types so that a user 'A' cannot affect a file which contains some other user 'B'southward' vital information/information. Information technology is like you do not want your colleague, who works on your Linux reckoner, to view your images. This is where Permissions set in, and they define user behavior.

Let the states understand the Permission system on Linux.

Linux File Permissions

Every file and directory in your UNIX/Linux system has following 3 permissions defined for all the iii owners discussed above.

• Read: This permission give you the dominance to open and read a file. Read permission on a directory gives you the power to lists its content.
• Write: The write permission gives yous the authority to modify the contents of a file. The write permission on a directory gives y'all the authority to add, remove and rename files stored in the directory. Consider a scenario where you take to write permission on file but do not accept write permission on the directory where the file is stored. You will be able to modify the file contents. But you volition not be able to rename, move or remove the file from the directory.
• Execute: In Windows, an executable program usually has an extension ".exe" and which you can easily run. In Unix/Linux, you cannot run a program unless the execute permission is set. If the execute permission is not set, you might still be able to run into/modify the programme code(provided read & write permissions are gear up), but not run it.

File Permissions in Linux/Unix

Let's come across file permissions in Linux with examples:

ls – l on terminal gives

ls - l

Here, we have highlighted '-rw-rw-r–'and this weird looking lawmaking is the one that tells the states nearly the Unix permissions given to the possessor, user grouping and the earth.

Here, the first '–' implies that we have selected a file.p>

Else, if information technology were a directory, d would have been shown.

The characters are pretty easy to remember.

r = read permission
w = write permission
x = execute permission
– = no permission

Permit u.s.a. wait at it this way.

The first role of the code is 'rw-'. This suggests that the owner 'Home' can:

• Read the file
• Write or edit the file
• He cannot execute the file since the execute fleck is set to '-'.

By pattern, many Linux distributions like Fedora, CentOS, Ubuntu, etc. will add users to a group of the same group proper name as the user proper name. Thus, a user 'tom' is added to a group named 'tom'.

The second part is 'rw-'. It for the user group 'Home' and group-members can:

• Read the file
• Write or edit the file

The third function is for the world which ways whatsoever user. It says 'r–'. This means the user can simply:

• Read the file

Changing file/directory permissions in Linux Using 'chmod' control

Say you practise non want your colleague to meet your personal images. This can be achieved past changing file permissions.

We can use the 'chmod' command which stands for 'alter way'. Using the command, nosotros can fix permissions (read, write, execute) on a file/directory for the possessor, group and the globe.

Syntax:

chmod permissions filename

In that location are two means to use the command –

1. Absolute mode
2. Symbolic mode

Absolute(Numeric) Mode in Linux

In this manner, file permissions are not represented as characters but a three-digit octal number.

The table below gives numbers for all for permissions types.

Number	Permission Type	Symbol
0	No Permission	—
1	Execute	–10
2	Write	-w-
iii	Execute + Write	-wx
4	Read	r–
five	Read + Execute	r-x
vi	Read +Write	rw-
7	Read + Write +Execute	rwx

Let's see the chmod permissions command in activity.

In the above-given concluding window, we accept inverse the permissions of the file 'sample to '764'.

'764' absolute code says the following:

• Possessor can read, write and execute
• Usergroup can read and write
• World tin only read

This is shown as '-rwxrw-r–

This is how you can change user permissions in Linux on file past assigning an absolute number.

Symbolic Fashion in Linux

In the Absolute mode, you change permissions for all 3 owners. In the symbolic style, you can modify permissions of a specific possessor. Information technology makes utilize of mathematical symbols to modify the Unix file permissions.

Operator	Description
+	Adds a permission to a file or directory
–	Removes the permission
=	Sets the permission and overrides the permissions set earlier.

The various owners are represented equally –

User Denotations
u	user/possessor
m	grouping
o	other
a	all

Nosotros will not exist using permissions in numbers like 755 but characters like rwx. Allow'due south look into an example

Changing Ownership and Group in Linux

For changing the ownership of a file/directory, you tin utilize the post-obit command:

chown user filename

In instance y'all desire to change the user as well equally group for a file or directory use the command

chown user:group filename

Let's see this in activity

In case you want to alter group-owner only, utilize the control

chgrp group_name filename

'chgrp' stands for change grouping.

Tip

• The file /etc/grouping contains all the groups defined in the system
• You can use the control "groups" to notice all the groups you are a fellow member of



• You can use the control newgrp to piece of work as a member a group other than your default grouping



• Y'all cannot have 2 groups owning the same file.
• You practise not have nested groups in Linux. One grouping cannot be sub-grouping of other
• x- eXecuting a directory means Existence allowed to "enter" a dir and proceeds possible access to sub-dirs
• There are other permissions that y'all can set on Files and Directories which will exist covered in a later avant-garde tutorial

Summary:

• Linux being a multi-user organisation uses permissions and ownership for security.
• There are 3 user types on a Linux system viz. User, Group and Other
• Linux divides the file permissions into read, write and execute denoted by r,westward, and x
• The permissions on a file can be changed past 'chmod' command which can be further divided into Absolute and Symbolic manner
• The 'chown' control can change the ownership of a file/directory. Utilize the following commands: chown user file or chown user:group file
• The 'chgrp' command can modify the grouping ownership chrgrp group filename
• What does x – eXecuting a directory mean? A: Being allowed to "enter" a dir and gain possible access to sub-dirs.

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Source: https://www.guru99.com/file-permissions.html

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