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DevOps

Linux Permission Calculator

Calculate Linux file permissions and their numeric chmod representation.

Features

  • Set read, write, and execute permissions
  • Display symbolic and octal modes
  • Generate a chmod command

How to use it

  1. Choose permissions for the owner, group, and others.
  2. Review the symbolic and numeric results.
  3. Copy the chmod command if needed.

Example and use cases

Calculate the octal permission value for a file that is readable and writable by its owner and readable by others.

Useful for understanding Unix permissions and checking chmod values before changing file access.

Linux & DevOps Tool

Linux Permission Calculator

Calculate Linux file and directory permissions using numeric and symbolic notation. Generate the correct chmod command instantly.

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Set permissions

Select read, write and execute permissions.

644

Enter three octal digits such as 644, 755 or 700.

Owner

u

6

Group

g

4

Others

o

4

Permission Result

Numeric and symbolic representations of your permissions.

Numeric

644

Symbolic

rw-r--r--

ls -l representation

-rw-r--r--

chmod command

chmod 644 example.txt

Permission breakdown

owner

Read and write

6

group

Read only

4

others

Read only

4
Total permission value14/21

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What are Linux file permissions?

Linux file permissions control who can read, modify or execute a file or directory. Every filesystem object has permissions for three categories: the owner, the group and other users.

Each category can have three basic permissions: read (r), write (w) and execute (x). Linux represents these permissions using symbolic notation such asrwxr-xr-xor numeric notation such as755.

How chmod numbers work

Each permission has a numeric value. Add the values for read, write and execute to calculate the permission digit.

r4

Read

View file contents or list a directory.

w2

Write

Modify a file or change directory contents.

x1

Execute

Execute a program or access a directory.

ValuePermissionMeaning
0---No permission
1--xExecute
2-w-Write
3-wxWrite + execute
4r--Read
5r-xRead + execute
6rw-Read + write
7rwxRead + write + execute

Common Linux permissions

644rw-r--r--

Common use: Regular files

755rwxr-xr-x

Common use: Executable files and directories

700rwx------

Common use: Private files and directories

600rw-------

Common use: Private configuration or key files

775rwxrwxr-x

Common use: Shared directories

777rwxrwxrwx

Common use: Full access for everyone

Be careful with chmod 777

chmod 777 grants read, write and execute permissions to the owner, group and everyone else. This can create unnecessary security exposure. Use the least permissions required for the application or user.

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FAQ

Linux Permission Calculator FAQ

What does chmod 755 mean?

chmod 755 gives the owner read, write and execute permissions, while the group and other users receive read and execute permissions.

What does chmod 644 mean?

chmod 644 gives the owner read and write permissions while the group and other users receive read-only access.

What does chmod 777 mean?

chmod 777 gives read, write and execute permissions to the owner, group and other users. It should generally be avoided unless there is a specific and understood requirement.

What do r, w and x mean in Linux?

r means read, w means write and x means execute. For directories, execute permission also controls whether a user can access entries within the directory.

What is chmod?

chmod is a Linux and Unix command used to change the permission mode of files and directories.

What is the difference between 755 and 644?

755 includes execute permission for the owner, group and others, while 644 provides read and write access to the owner and read-only access to group and others.

What permission should an SSH private key have?

SSH private keys are commonly protected with restrictive permissions such as 600 so that only the owner can read and modify the key.

What does chmod -R do?

The -R option applies a permission change recursively to a directory and the files and subdirectories beneath it. Review recursive changes carefully before applying them.

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Frequently asked questions

What does the numeric chmod value represent?

Each digit combines read, write, and execute bits for the owner, group, or others, respectively.

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