chmod 551 Permission Explained

Octal

551

Symbolic

r-xr-x--x

Binary

101 101 001

Risk Level

Low Risk

Summary: chmod 551 gives the owner read/execute, the group read/execute, and everyone else execute.

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

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

Octal

Symbolic

Target File / Path

-R Recursive -v Verbose

551

r-xr-x--x

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

chmod 551 filename

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

View the full chmod 551 guide →

chmod 551 Breakdown

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

Is chmod 551 Safe?

Low Risk

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

Common Use Cases

551 is uncommon in standard Linux setups. The closest widely used permission is chmod 555.

chmod 551 Command Examples

# Apply using octal mode
chmod 551 filename

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

# Recursive command warning:
chmod -R 551 /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 551 {} +

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

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

umask Relationship

A umask of 226 makes new directories 551. Test umask values with our interactive Umask Calculator.

Frequently Asked Questions

What does chmod 551 mean?

chmod 551 gives the owner read/execute, the group read/execute, and everyone else execute. In octal notation, the owner receives 5 (read/execute), the group receives 5 (read/execute), and others receive 1 (execute).

Is chmod 551 safe?

chmod 551 is classified as Low Risk. Even the owner cannot modify this file without changing permissions first.

What is chmod 551 in symbolic notation?

In symbolic notation, chmod 551 is represented as r-xr-x--x. You can apply this permission using the equivalent symbolic command "chmod u=rx,g=rx,o=x filename".