chmod 511 Permission Explained

Octal

511

Symbolic

r-x--x--x

Binary

101 001 001

Risk Level

Low Risk

Summary: chmod 511 gives the owner read/execute, the group execute, and everyone else execute.

Class	Read (4)	Write (2)	Execute (1)	Octal
Owner (u)				5
Group (g)				1
Others (o)				1

setuid (4) setgid (2) sticky bit (1)

Octal

Symbolic

Target File / Path

-R Recursive -v Verbose

511

r-x--x--x

Owner: read/execute · Group: execute · Others: execute

chmod 511 filename

Low Risk Even the owner cannot modify this file without changing permissions first.

View the full chmod 511 guide →

chmod 511 Breakdown

Class	Digit	Symbolic	On a file	On a directory
Owner (u)	`5`	`r-x`	Read and execute	Can list and enter
Group (g)	`1`	`--x`	Execute only	Can enter (cd) but not list contents
Others (o)	`1`	`--x`	Execute only	Can enter (cd) but not list contents

Is chmod 511 Safe?

Low Risk

Even the owner cannot modify this file without changing permissions first.

Common Use Cases

511 is uncommon in standard Linux setups. The closest widely used permission is chmod 711.

chmod 511 Command Examples

# Apply using octal mode
chmod 511 filename

# Apply using equivalent symbolic mode
chmod u=rx,g=x,o=x filename

# Recursive command warning:
chmod -R 511 /path/to/dir
# Note: -R applies the same mode to files and directories. Use find to treat them separately:
find /path/to/dir -type d -exec chmod 511 {} +

# Verify permissions
stat -c '%a %A %n' filename    # Linux
stat -f '%Lp %Sp %N' filename   # macOS

# Example ls -l output:
-r-x--x--x 1 alice staff 1024 Jan 15 10:00 example.txt

umask Relationship

A umask of 266 makes new directories 511. Test umask values with our interactive Umask Calculator.

Frequently Asked Questions

What does chmod 511 mean?

chmod 511 gives the owner read/execute, the group execute, and everyone else execute. In octal notation, the owner receives 5 (read/execute), the group receives 1 (execute), and others receive 1 (execute).

Is chmod 511 safe?

chmod 511 is classified as Low Risk. Even the owner cannot modify this file without changing permissions first.

What is chmod 511 in symbolic notation?

In symbolic notation, chmod 511 is represented as r-x--x--x. You can apply this permission using the equivalent symbolic command "chmod u=rx,g=x,o=x filename".