chmod 755 Explained — Owner Full, Others Read+Execute

What Does chmod 755 Mean?

The permission 755 is one of the most commonly used Linux file permissions. It breaks down into three octal digits, each representing a sum of permission bits:

Role	Octal	Binary	Symbolic	Permissions
Owner	7	111	rwx	Read + Write + Execute
Group	5	101	r-x	Read + Execute
Others	5	101	r-x	Read + Execute

Why 755?

Permission 755 follows the principle of least privilege for public resources:

• The owner (typically the user who created the file or a service account) has full control: they can read the content, modify it, and execute it.
• Group members and other users can read and execute but cannot modify. This prevents accidental or malicious changes while still allowing the file to be used.

Where Is 755 Used?

# Executable scripts and binaries
chmod 755 /usr/local/bin/my-script.sh

# Public directories (web root, project dirs)
chmod 755 /var/www/html

# System directories
ls -ld /usr /usr/bin /usr/local
# drwxr-xr-x ...

755 for Directories vs Files

For directories, execute permission means the ability to cd into the directory and access files within it. Without execute on a directory, users cannot traverse it even if they have read permission.

For files, execute permission means the file can be run as a program. Regular data files (text, images, configs) should typically NOT have execute permission.

Security Considerations

Permission 755 is generally safe for files that are intended to be publicly readable and executable. However, configuration files containing secrets should use more restrictive permissions like 600 or 640.