chmod 406 Permission Explained
Summary: chmod 406 gives the owner read, the group no access, and everyone else read/write.
| Class | Read (4) | Write (2) | Execute (1) | Octal |
|---|---|---|---|---|
| Owner (u) | 4 | |||
| Group (g) | 0 | |||
| Others (o) | 6 |
chmod 406 filename
chmod 406 Breakdown
| Class | Digit | Symbolic | On a file | On a directory |
|---|---|---|---|---|
| Owner (u) | 4 |
r-- |
Read only | Can list names, but not enter |
| Group (g) | 0 |
--- |
No access | Cannot list, enter, or modify |
| Others (o) | 6 |
rw- |
Read and write | Can list names, cannot enter |
Is chmod 406 Safe?
Critical Risk
- Anyone on the system can modify or replace this file.
- Any user can read this file — never use it for secrets such as keys or .env files.
- Even the owner cannot modify this file without changing permissions first.
- Unusual: a lower class has permissions the class above it lacks.
Common Use Cases
406 is uncommon in standard Linux setups. The closest widely used permission is chmod 400.
chmod 406 Command Examples
# Apply using octal mode
chmod 406 filename
# Apply using equivalent symbolic mode
chmod u=r,g=,o=rw filename
# Recursive command warning:
chmod -R 406 /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 406 {} +
# Verify permissions
stat -c '%a %A %n' filename # Linux
stat -f '%Lp %Sp %N' filename # macOS
# Example ls -l output:
-r-----rw- 1 alice staff 1024 Jan 15 10:00 example.txtumask Relationship
A umask of 371 makes new directories 406 and new files 406. Test umask values with our interactive Umask Calculator.
Frequently Asked Questions
What does chmod 406 mean?
chmod 406 gives the owner read, the group no access, and everyone else read/write. In octal notation, the owner receives 4 (read), the group receives 0 (no access), and others receive 6 (read/write).
Is chmod 406 safe?
chmod 406 is classified as Critical Risk. Anyone on the system can modify or replace this file.
What is chmod 406 in symbolic notation?
In symbolic notation, chmod 406 is represented as r-----rw-. You can apply this permission using the equivalent symbolic command "chmod u=r,g=,o=rw filename".
Related Permissions
Change one bit: