chmod 177 — the --xrwxrwx permission
177 is --xrwxrwx. The owner gets x, and everyone else gets rwx. Anyone at all can change it.
Anyone can change it · The write bit is open to everyone. Anybody who reaches this machine can change the contents, so keep it away from web folders and config files.
Who can do what
Three rows for owner, group and others; three columns for read, write and execute. On a folder that last one means the right to go inside.
| Read | Write | Execute | |
|---|---|---|---|
| Owner1 | · | · | ✓ |
| Group7 | ✓ | ✓ | ✓ |
| Others7 | ✓ | ✓ | ✓ |
On a folder the execute bit means going inside. With read but no execute you can list the names yet open nothing in it.
- Symbolic
- --xrwxrwx
- ls -l (file)
- ---xrwxrwx
- ls -l (directory)
- d--xrwxrwx
- chmod symbolic form
- chmod u=x,g=rwx,o=rwx
- Command
- chmod 177 <file>
- Binary
- 001111111
- Decimal
- 127
- umask (directory)
- 600
- umask (file)
- Not reachable — new files never start with the execute bit
One digit away
How to read this
- Read is 4, write 2, execute 1; add them for one digit. 7 is 4+2+1, 5 is 4+1.
- The digits are owner, group, others, left to right.
- umask is what gets taken away: from 777 for directories, from 666 for files.
- Special bits (setuid 4000, setgid 2000, sticky 1000) add a fourth digit in front — /tmp is 1777.
Frequently asked questions
Q. What does chmod 177 mean?
It is --xrwxrwx. ls -l shows a file as ---xrwxrwx and a directory as d--xrwxrwx.
Q. How is 177 written in rwx form?
It is the same as chmod u=x,g=rwx,o=rwx.
Q. What can other people do with 177?
They get rwx — write included, so anyone can change the contents.
Q. Which umask produces 177?
600 for directories. For files it cannot be reached by umask alone, since new files never carry the execute bit.