chmod 660 Permission Explained: Group-Private Read/Write

Octal

660

Symbolic

rw-rw----

Binary

110 110 000

Risk Level

Moderate

Summary: Owner and group edit; others have no access.

Class	Read (4)	Write (2)	Execute (1)	Octal
Owner (u)				6
Group (g)				6
Others (o)				0

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

Octal

Symbolic

Target File / Path

-R Recursive -v Verbose

660

rw-rw----

Owner: read/write · Group: read/write · Others: no access

chmod 660 filename

Moderate Every member of the group can modify this file.

View the full chmod 660 guide →

chmod 660 Breakdown

Class	Digit	Symbolic	On a file	On a directory
Owner (u)	`6`	`rw-`	Read and write	Can list names, cannot enter
Group (g)	`6`	`rw-`	Read and write	Can list names, cannot enter
Others (o)	`0`	`---`	No access	Cannot list, enter, or modify

Is chmod 660 Safe?

Moderate

Every member of the group can modify this file.

When not to use it

Static assets or documentation that public web visitors need to read

Common Use Cases

Inter-process communication Unix domain sockets
Database dump files and internal shared logs restricted to a service group

chmod 660 Command Examples

# Apply using octal mode
chmod 660 filename

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

# Recursive command warning:
chmod -R 660 /path/to/dir
# Note: -R applies the same mode to files and directories. Use find to treat them separately:
find /path/to/dir -type f -exec chmod 660 {} +

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

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

umask Relationship

A umask of 117 makes new directories 660 and new files 660. Test umask values with our interactive Umask Calculator.

Frequently Asked Questions

What does chmod 660 mean?

Owner and group edit; others have no access. In octal notation, the owner receives 6 (read/write), the group receives 6 (read/write), and others receive 0 (no access).

Is chmod 660 safe?

chmod 660 is classified as Moderate. Every member of the group can modify this file.

What is chmod 660 in symbolic notation?

In symbolic notation, chmod 660 is represented as rw-rw----. You can apply this permission using the equivalent symbolic command "chmod u=rw,g=rw,o= filename".

Related Permissions

Change one bit:

chmod 260 remove owner read chmod 460 remove owner write chmod 760 add owner execute chmod 620 remove group read chmod 640 remove group write chmod 670 add group execute chmod 664 add others read chmod 662 add others write chmod 661 add others execute

← chmod 657 chmod 661 →

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