chmod 151 Permission Explained

Notice: This is an unusual permission set: some classes have more access than the class above them. It is rarely correct in practice.

Octal

151

Symbolic

--xr-x--x

Binary

001 101 001

Risk Level

Low Risk

Summary: chmod 151 gives the owner execute, the group read/execute, and everyone else execute.

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

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

Octal

Symbolic

Target File / Path

-R Recursive -v Verbose

151

--xr-x--x

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

chmod 151 filename

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

View the full chmod 151 guide →

chmod 151 Breakdown

Class	Digit	Symbolic	On a file	On a directory
Owner (u)	`1`	`--x`	Execute only	Can enter (cd) but not list contents
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 151 Safe?

Low Risk

Even the owner cannot modify this file without changing permissions first.
Scripts need read permission to run; only compiled binaries can be executed without it.
Unusual: a lower class has permissions the class above it lacks.

Common Use Cases

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

chmod 151 Command Examples

# Apply using octal mode
chmod 151 filename

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

# Recursive command warning:
chmod -R 151 /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 151 {} +

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

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

umask Relationship

A umask of 626 makes new directories 151. Test umask values with our interactive Umask Calculator.

Frequently Asked Questions

What does chmod 151 mean?

chmod 151 gives the owner execute, the group read/execute, and everyone else execute. In octal notation, the owner receives 1 (execute), the group receives 5 (read/execute), and others receive 1 (execute).

Is chmod 151 safe?

chmod 151 is classified as Low Risk. Even the owner cannot modify this file without changing permissions first.

What is chmod 151 in symbolic notation?

In symbolic notation, chmod 151 is represented as --xr-x--x. You can apply this permission using the equivalent symbolic command "chmod u=x,g=rx,o=x filename".