Chmod Permissions Calculator
Visually calculate and convert Linux file permissions between numeric octal codes, symbolic notations, and shell commands.
👤 Owner (User)
7👥 Group
5🌐 Others (Public)
5What is Chmod?
`chmod` (change mode) is the Unix/Linux command used to change file and directory access permissions. Permissions specify who can read, write, or execute a file across three user categories: Owner, Group, and Public/Others.
Key Features
- Interactive Checkboxes: Click read, write, or execute permissions to see numeric and symbolic codes update in real-time.
- Command Builder: Enter a file or folder path and toggle `-R` (recursive) to generate ready-to-run terminal commands.
- Standard Presets: One-click configurations for common web file (644), script/folder (755), and SSH key (600/400) permissions.
- Security Best Practices: Clear guidance on avoiding insecure permissions like 777 in production environments.
Frequently Asked Questions
What does chmod 755 mean?▼
755 gives the Owner read, write, and execute permissions (4+2+1 = 7). Group and Others have read and execute permissions (4+1 = 5). This is the standard setting for web directories and executable scripts.
Why is chmod 777 dangerous?▼
Chmod 777 allows anyone on the server to read, modify, and execute files. On shared servers or web applications, this creates severe security vulnerabilities where malicious actors could overwrite files or upload backdoors.
What permissions should SSH keys have?▼
Private SSH keys (such as `~/.ssh/id_rsa`) must be strictly protected with `chmod 600` (read/write for owner only) or `chmod 400` (read only for owner). SSH clients will refuse to use keys with loose permissions.
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