Linux Permissions:

Chmod Calculator is a free utility to calculate the numeric (octal) or symbolic value for a set of file or folder permissions in unix or unix-like systems such as linux or ubuntu.

How it Works?

Check the desired boxes or directly enter a valid numeric value (e.g. 777) or symbolic notation (e.g. rwxrwxrwx) to see its value in other formats.

How to use chmod?

You can change file permissions in this format:
chmod [options] [mode] [file_name]


What are permissions?

Each file on a system has a set of permissions associated with it, meaning which users have access and what type of access they have.

There are three types of users:

  1. User, meaning the user who owns the file
  2. Group, meaning the files defined ownership group
  3. Other, meaning everyone else

File permissions in Linux file system are managed in three distinct user classes: user/owner, group and others/public. Each class can have read, write and execute permissions. File permission can be represented in a symbolic or numeric (octal) format.

Examples

Chmod examples in octal mode:

Readable by owner only

$ chmod 400 chmodExample.txt

Readable by group only

$ chmod 040 chmodExample.txt

Readable by anyone

$ chmod 004 chmodExample.txt

Writeable by owner only

$ chmod 200 chmodExample.txt

Writeable by group only

$ chmod 020 chmodExample.txt

Writeable by anyone

$ chmod 002 chmodExample.txt

Executeable by owner only

$ chmod 100 chmodExample.txt

Executeable by group only

$ chmod 010 chmodExample.txt

Executeable by anyone

$ chmod 001 chmodExample.txt

Allow read permission to owner and group and anyone.

$ chmod 444 chmodExample.txt

Allow everyone to read, write, and execute file.

$ chmod 777 chmodExample.txt
Chmod examples in symbolic mode:

Deny execute permission to everyone.

$ chmod a-x chmodExampleFile.txt

Allow read permission to everyone.

$ chmod a+r chmodExampleFile.txt

Make a file readable and writable by the group and others.

$ chmod go+rw chmodExampleFile.txt

Make a shell script executable by the user/owner.

$ chmod u+x chmodExampleScript.sh

Allow everyone to read, write, and execute the file and turn on the set group-ID.

$ chmod =rwx,g+s chmodExampleScript.sh