Chmod Calculator
Visual permissions generator for Linux/Unix files. Convert between numeric (octal) and symbolic formats.
Linux Permissions (Octal)
e.g. 755Symbolic Notation
e.g. -rwxr-xr-xCommand
Understanding Linux Permissions
Linux and Unix-like operating systems use a permissions system to control access to files and directories. These can be represented numerically (octal) or symbolically.
Owner
The user who owns the file. Usually the creator. Permissions here apply only to this specific user.
Group
A defined group of users. Any user in this group will have these permissions, unless they are the owner.
Public / Other
Everyone else. Be careful with write permissions here, as it allows anyone on the system to modify the file.
Common Permission Presets
- 777 (rwxrwxrwx) Full access for everyone (Insecure)
- 755 (rwxr-xr-x) Owner full, others read/execute (Web Standard)
- 644 (rw-r--r--) Owner read/write, others read only (Files)
- 600 (rw-------) Private to owner only (Keys/Secrets)
Frequently Asked Questions
Example: Read + Write = 4 + 2 = 6.
Read + Execute = 4 + 1 = 5.
-R flag. For example, chmod -R 755 /path/to/directory will apply the permissions to the directory and everyone file/folder inside it.
chmod changes who can do what (permissions), while chown changes who owns the file (ownership). You often need to use both.
u stands for User (Owner), + means add permission, and x means Execute. So it adds execute permission for the owner.
sudo before your command to run it as root (e.g., sudo chmod 755 file).
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