Chmod Permission Calculator
Free online chmod calculator to set Unix/Linux file permissions. Convert between octal, symbolic notation, and get the chmod command instantly.
| Role | Read | Write | Execute |
|---|---|---|---|
| Owner | |||
| Group | |||
| Other |
Octal
644
Symbolic
rw-r--r--
Command
chmod 644 filename
What Is a Chmod Permission Calculator?
A chmod permission calculator helps you determine the correct Unix/Linux file permission values by visually toggling read, write, and execute permissions for the owner, group, and other users. It instantly converts between the octal notation (like 755) and symbolic notation (like rwxr-xr-x), and generates the ready-to-use chmod command for your terminal.
How to Use the Chmod Permission Calculator
- Use the checkboxes to toggle read, write, and execute permissions for owner, group, and other users.
- Observe the octal value, symbolic representation, and chmod command update in real time.
- Alternatively, use the preset buttons (755, 644, etc.) to quickly apply common permission configurations.
- You can also enter an octal value directly and click Apply to set the corresponding checkboxes.
- Copy the generated chmod command to use in your terminal.
Use Cases
- Setting File Permissions on Servers — Quickly determine the correct chmod value when configuring web server files, SSH keys, or deployment scripts to ensure proper security.
- Understanding Permission Notation — Learn how octal and symbolic permission notations map to actual file access rights for owner, group, and other users.
- Security Auditing — Verify file permissions during security reviews by converting between octal and symbolic formats to check for overly permissive settings.
- DevOps & Automation — Generate correct permission values for Dockerfiles, shell scripts, Ansible playbooks, and other infrastructure configuration files.
FAQ
What does chmod 755 mean?
chmod 755 sets permissions to rwxr-xr-x, meaning the owner can read, write, and execute the file, while group members and other users can only read and execute it. This is commonly used for executable scripts and web directories.
What is the difference between octal and symbolic notation?
Octal notation uses three digits (e.g., 644) where each digit represents permissions for owner, group, and others. Symbolic notation uses letters r (read), w (write), and x (execute) with dashes for denied permissions (e.g., rw-r--r--). Both represent the same permissions.
What permission should I use for SSH keys?
SSH private keys should be set to 600 (rw-------), meaning only the owner can read and write the file. The SSH directory itself should be 700 (rwx------). SSH will refuse to use keys with overly permissive settings.
Why should I avoid chmod 777?
chmod 777 grants full read, write, and execute permissions to everyone, creating a significant security risk. Any user on the system can modify or execute the file, which could lead to unauthorized access or code execution.