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This chmod cheat sheet covers Unix file permissions: what the numbers mean, the common values, and the symbolic notation. To build any permission without memorizing it, use the Chmod Calculator.
The permission digits
Each of the three digits in a value like 755 sets permissions for the owner, the group, and everyone else. Each digit is the sum of read (4), write (2), and execute (1).
| Number | Permission | Symbolic |
|---|---|---|
| 7 | read, write, execute | rwx |
| 6 | read, write | rw- |
| 5 | read, execute | r-x |
| 4 | read | r– |
| 3 | write, execute | -wx |
| 2 | write | -w- |
| 1 | execute | –x |
| 0 | none | — |
Common permission values
| Value | Meaning | Typical use |
|---|---|---|
| 644 | owner read/write, others read | Regular files |
| 755 | owner all, others read/execute | Folders and scripts |
| 600 | owner read/write only | Private files and keys |
| 700 | owner all, no one else | Private folders |
| 777 | everyone can do everything | Avoid, insecure |
| 400 | owner read only | Locked files |
Symbolic notation
Instead of numbers you can use letters: u owner, g group, o others, a all, with + to add, – to remove, and = to set. For example, chmod u+x file adds execute for the owner, and chmod go-w file removes write for group and others.
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Frequently asked questions
What does chmod 755 mean?
The owner can read, write, and execute, while the group and everyone else can read and execute. It is common for folders and scripts.
What is the difference between 644 and 755?
644 has no execute bit, which suits regular files, while 755 adds execute, which folders and runnable scripts need.
Is chmod 777 safe?
No. It lets anyone read, write, and execute the file, so avoid it and use the least permission that works.