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Unix File Permissions — chmod, chown, and Linux Permission System

Unix file permissions control read, write, and execute access. This guide covers octal notation, chmod, and web server configurations.

Dev Utilities Team
••1 min read
Unix File Permissions — chmod, chown, and Linux Permission System

Common permission sets

ItemPermissionReason
Directories755Owner can write; web server can traverse
PHP/HTML files644Owner can write; web server reads
.env / config600Only owner reads secrets
SSH private key600SSH refuses keys readable by others

Never use 777 in production — it allows any user on the server to modify your files.

Calculate permissions with our chmod Calculator.

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