chmod 642 Permission Explained
Summary: chmod 642 gives the owner read/write, the group read, and everyone else write.
| Class | Read (4) | Write (2) | Execute (1) | Octal |
|---|---|---|---|---|
| Owner (u) | 6 | |||
| Group (g) | 4 | |||
| Others (o) | 2 |
chmod 642 filename
chmod 642 Breakdown
| Class | Digit | Symbolic | On a file | On a directory |
|---|---|---|---|---|
| Owner (u) | 6 |
rw- |
Read and write | Can list names, cannot enter |
| Group (g) | 4 |
r-- |
Read only | Can list names, but not enter |
| Others (o) | 2 |
-w- |
Write only (rarely useful) | No practical effect without x |
Is chmod 642 Safe?
Critical Risk
- Anyone on the system can modify or replace this file.
- Unusual: a lower class has permissions the class above it lacks.
Common Use Cases
642 is uncommon in standard Linux setups. The closest widely used permission is chmod 640.
chmod 642 Command Examples
# Apply using octal mode
chmod 642 filename
# Apply using equivalent symbolic mode
chmod u=rw,g=r,o=w filename
# Recursive command warning:
chmod -R 642 /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 642 {} +
# Verify permissions
stat -c '%a %A %n' filename # Linux
stat -f '%Lp %Sp %N' filename # macOS
# Example ls -l output:
-rw-r---w- 1 alice staff 1024 Jan 15 10:00 example.txtumask Relationship
A umask of 135 makes new directories 642 and new files 642. Test umask values with our interactive Umask Calculator.
Frequently Asked Questions
What does chmod 642 mean?
chmod 642 gives the owner read/write, the group read, and everyone else write. In octal notation, the owner receives 6 (read/write), the group receives 4 (read), and others receive 2 (write).
Is chmod 642 safe?
chmod 642 is classified as Critical Risk. Anyone on the system can modify or replace this file.
What is chmod 642 in symbolic notation?
In symbolic notation, chmod 642 is represented as rw-r---w-. You can apply this permission using the equivalent symbolic command "chmod u=rw,g=r,o=w filename".
Related Permissions
Change one bit: