What Does CHMOD 644 Mean?
CHMOD 644 sets read and write permissions for the file owner, while granting read-only access to group members and the general public.
Owner (User)
Read + Write (4+2+0)The file owner can read and edit the file contents, but cannot execute it as a program.
Group
Read Only (4+0+0)Group members can read the file, but cannot modify or execute it.
Others (Public)
Read Only (4+0+0)All other users (including web server visitors) can view or download the file.
Why 644 is the Standard for Web Files
On Linux servers hosting web content, files like index.html, styles.css, and image assets must be readable by HTTP server processes like Nginx or Apache.
Setting files to 644 ensures:
- The web server can read and serve the file to website visitors.
- No external user or web client can modify the file content on disk.
- The file cannot be executed as a program, preventing malicious code execution even if uploaded.
File Permissions vs Executable Bits
Regular documents and static web assets should almost never have the execute bit (x) enabled. Enabling execute permission on regular files is unnecessary and creates security vectors. If a file does not need to run as a binary or shell script, 644 is the correct standard.
How to Apply CHMOD 644
chmod 644 index.html# Recursively set 644 on all regular files inside a folderfind /var/www/html -type f -exec chmod 644 +