What is 755 in linux

What Does File Permission 755 Mean?

In Linux, the file permissions are the owner’s rights. The owner can share the rights of its file with different users by defining some conditions. The permissions are represented in specific alphabets and octal values.

This post will briefly describe the “755” permission in Linux. Alongside that, we will also explain the basics of permissions in Linux. The content of this post is as follows:

Let’s start with the basic understanding.

Understanding of the File Permissions in Linux

Before proceeding to the meaning of “File Permission 755”, it is compulsory for the readers to be well known for file permission in Linux.

In Linux, there are always three types of users for using the files. These users are:

Permissions w.r.t Users

Owner	This is the owner of the file who created it
Group	This is a group of users which can access the file on some granted permissions
Other users	Other than these, users should be considered in this category of the users. These users also include guest users.

Various types of permissions can be granted to the users; these permissions are described in the following table.

Permission	Description	Representation
Alphabetical	Octal
Read	Read Permissions	r	4
Write	Write Permissions	w	2
Execute	Execute Permissions	x	1

Let’s understand it more clearly through an example.

In the above figure, the permissions of different users are as follows:

• User and the group has the read (r) and write (w) permissions.
• Other users are allowed only to read the file.

If we talk about the same permissions in octal representation, it becomes “664”, which can be understood from the following table.

Permissions	Owner	Group	Other Users
Read	4	4	4
Write	2	2	0
Execute	0	0	0
Total	6	6	4

The first digit of the 664 explains the permissions of the owner, the second digit explains the permissions of the group, and the last digit, explains the permissions of the other users.

What Does the File Permission 755 Mean?

Following the example stated in the previous section, we can demonstrate the “755” permission in the following manner:

Permissions	Owner	Group	Other Users
Read	4	4	4
Write	2	0	0
Execute	1	1	1
Total	7	5	5

Let’s understand it more clearly:

• “7” shows that the “Owner” has the read(r), write(w), and execute(x) permissions.
• “5” represents that the “Group” has read(r) and execute(x) permissions only.
• The last “5” means that the “Other Users” have read(r) and execute(x) rights.

Example: Grant 755 Permissions to a File

To understand the 755 file permissions, we will create a file with the name “MyFile” using the command:

Now, we will set the permissions of the file to “755” using the “chmod” command utility as follows:

To display the permissions of the file, MyFile, we will list down the contents:

In the above figure, we can see that the owner of the file has full access( read, write, and execute), the group and other users have only read and execute permissions.

This is all about the 755 permissions in Linux.

Conclusion

In Linux, the file permissions 755 means that the owner has full access (read, write, and execute permissions), and the remaining users have only read and execute rights. The “7”, “5”, and “5” are the octal representations of “r, w, x”, “r,x”, and “r, x”, respectively. This post has briefly explained the file permission “755” in Linux.

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What is the Meaning of chmod 755, and How to execute and Verify It?

In Linux, chmod is a built-in command that manages the access permission of file objects (files and directories). It can assign groups, users, and others to have permission for executing, reading, and writing permission on a certain file or directory.

The number defined after chmod represents the permissions. The chmod 775 is an essential command that assigns read, write, and execute permission to a specific user, group, or others.

In this guide, check out how to use chmod 755.

Chmod basics

Before diving deeper, let’s have a look at the basics of chmod. Because Linux is a multi-user system, it’s important to have a proper file permission system that controls user access. For any file or directory, there are 3 types of permissions.

Using the chmod command, it can set custom permissions to files and directories. Here’s the command structure of any chmod command.

For this guide, we’ll be focusing on the chmod 755 commands.

User and group ownership

First, run the following ls command. It’ll print information about the files and directories under the home directory.

Have a look at the left column. It may look like gibberish, but it actually encodes the file permissions. For example, the first character of the first column describes whether it’s a file or a directory. For a directory, the value will be “d”. For a single file, the value will be “-“.

The third column indicates the “user owner” of the file/directory. It’s the user who created this specific file/directory.

The fourth column indicates the “group owner”. It indicates the user group that has access to the file/directory. Any user from the group can access the file/directory.

Read, write and execute permissions

As mentioned earlier, the first character indicates whether it’s a file or a directory. What do the next characters mean? Here’s a quick breakdown.

• Character 1: File (-) or directory (d).
• Character 2-4: Permission for the user owner.
• Character 5-7: Permission for the group owner.
• Character 8-10: Permission for others, for example, users that aren’t the owner and not part of the user group.

Note that characters 2-10 feature only a handful of values.

The values will come in the form of “rwx”. If a certain value is “-“, then the permission isn’t set. For example, “rw-“ means that the file has read and write permission but execute permission isn’t set.

How does the read, write, and execute permission apply to files and directories?

• Read
  • File: Reading file content.
  • Directory: Listing directory contents.
  • File: Modify the content of the file.
  • Directory: Rename, add, and delete files in the directory.
  • File: Defines an executable file, for example, a bash script.
  • Directory: Access the directory.

  Octal representation of permissions

  This leads back to our original question. What does the chmod 755 value mean?

  Instead of using characters, it’s also possible to use octal values to signify the permissions. The value ranges from 0 to 7 (in octal).

  Here, 755 is an octal expression of the permission “rwxr-xr-x”. Now, breaking down the chmod 755 value,

  • 7: 4 + 2 + 1: Read, write, and execute (user owner).
  • 5: 4 + 0 + 1: Read and execute permissions (group owner).
  • 5: 4 + 0 + 1: Read and execute permissions (others).

  Let’s break down chmod 644.

  • 6: 4 + 2 + 0: Read and write permissions for the user owner.
  • 4: 4 + 0 + 0: Read permission for the group owner.
  • 4: 4 + 0 + 0: Read permission for others.

  So, 644 signifies the file permission “rw-r–r–“.

  Applying chmod 755

  It’s time to put chmod 755 in action. To set the permission to 755, run the following chmod command.

  

  What if the directory contains one or more sub-directories? To apply chmod 755 to all the subsequent files and directories, run chmod in recursive mode.

  

  Verify the changes using the ls command.

  

  Final thoughts

  This guide covers a lot of concepts. It explains the basics of the chmod command, with an in-depth explanation of chmod values and their usage. It also demonstrates how to apply various chmod values to files and directories.

  For further examples, here’s an awesome guide on various chmod usage with examples. It demonstrates numerous applications of chmod with different values. The information from this guide will help to understand the steps better.

  A multi-user system must also have a robust user permission management system to control the behaviors of the users. In Linux, the sudoers file decides which users get to execute sudo commands. Learn more about how to add users to sudoers.

  About the author

  Sidratul Muntaha

  Student of CSE. I love Linux and playing with tech and gadgets. I use both Ubuntu and Linux Mint.

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  Linux chmod Example

  755 means read and execute access for everyone and also write access for the owner of the file. When you perform chmod 755 filename command you allow everyone to read and execute the file, the owner is allowed to write to the file as well.

  What is the meaning of chmod 777?

  Setting 777 permissions to a file or directory means that it will be readable, writable and executable by all users and may pose a huge security risk. . File ownership can be changed using the chown command and permissions with the chmod command.

  How do I chmod files in Linux?

  1. chmod +rwx filename to add permissions.
  2. chmod -rwx directoryname to remove permissions.
  3. chmod +x filename to allow executable permissions.
  4. chmod -wx filename to take out write and executable permissions.

  What does chmod 666 do?

  chmod 666 file/folder means that all users can read and write but cannot execute the file/folder; . chmod 744 file/folder allows only user (owner) to do all actions; group and other users are allowed only to read.

  What is chmod 744?

  744 , which is a typical default permission, allows read, write, and execute permissions for the owner, and read permissions for the group and “world” users. Either notation is equivalent, and you may choose to use whichever form more clearly expresses your permissions needs.

  Why is 777 permission dangerous?

  By giving 777 permissions to a file you can have all users read, write, and execute the same. This means that any vulnerability in your system allows an attacker to do as he likes with this file.

  What does chmod 555 do?

  What Does Chmod 555 Mean? Setting a file’s permissions to 555 makes it so that the file cannot be modified at all by anyone except the system’s superuser (learn more about the Linux superuser).

  What does chmod 775 mean?

  Chmod 775 (chmod a+rwx,o-w) sets permissions so that, (U)ser / owner can read, can write and can execute. ( G)roup can read, can write and can execute. ( O)thers can read, can’t write and can execute.

  How do I read chmod permissions?

  1. 0 = no permissions whatsoever; this person cannot read, write, or execute the file.
  2. 1 = execute only.
  3. 2 = write only.
  4. 3 = write and execute (1+2)
  5. 4 = read only.
  6. 5 = read and execute (4+1)
  7. 6 = read and write (4+2)
  8. 7 = read and write and execute (4+2+1)

  How do I chmod all files?

  1. Use chmod -R 755 /opt/lampp/htdocs if you want to change permissions of all files and directories at once.
  2. Use find /opt/lampp/htdocs -type d -exec chmod 755 \; if the number of files you are using is very large. .
  3. Use chmod 755 $(find /path/to/base/dir -type d) otherwise.
  4. Better to use the first one in any situation.

  How do I change chmod permissions?

  The chmod command enables you to change the permissions on a file. You must be superuser or the owner of a file or directory to change its permissions.
  .
  Changing File Permissions.

  Octal Value	File Permissions Set	Permissions Description
  5	r-x	Read and execute permissions
  6	rw-	Read and write permissions
  7	rwx	Read, write, and execute permissions

  

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