What does chmod 644 mean? File permissions for web servers, configs, and static content
chmod 644 sets permissions to rw-r--r--: the owner can read and write; the group and everyone else can only read. This is the standard permission for static files on web servers, configuration files, documents, and any file that should be viewable but not executable or editable by others.
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Calculate Linux file permissions using checkboxes, octal numbers, or symbolic notation.
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How this is calculated
In octal, 6 = 4+2+0 (read+write). 4 = 4+0+0 (read-only). 644 is safe because it prevents both accidental execution and unauthorized modification. On a web server, setting PHP or Python files to 644 ensures they can be read by the web server process but not written to if the server is compromised. Paired with 755 on directories, 644 on files creates a sensible security baseline for any shared or web-facing system.
Verdict
644 is the correct default for all non-executable files. It's what your text editor sets when you create a new file (subject to umask). If a file doesn't need to be run as a program and doesn't contain secrets, 644 is almost certainly the right permission.