What does chmod 755 mean?

Owner can read, write and execute. Group and others can read and execute. Common for scripts and directories.

What does chmod 644 mean?

Owner can read and write. Everyone else can read. Common for ordinary files.

What permissions should an SSH key have?

600 for the private key and 700 for the .ssh directory. OpenSSH refuses keys others can read.

What is the sticky bit?

On a directory, it stops users deleting files they do not own. /tmp is 1777.

chmod calculator — ToolDeck

What it does

Unix permissions have three sets of read, write and execute bits: for the owner, the group and everyone else. Each set is one octal digit (r=4, w=2, x=1), so 755 means owner rwx, group r-x, others r-x.

An optional fourth leading digit sets setuid (4), setgid (2) and sticky (1).

How to use it

Tick the boxes, or type an octal value or a symbolic string such as rwxr-xr-x.
Read the other forms and copy the chmod command.

Example

Input

Output

-rwxr-xr-x
chmod 755 file

Things to watch for

777 lets any user change the file. It is almost never the right fix for a permission error.
Directories need x to be entered and r to be listed.
setuid on a script is ignored by Linux; it only applies to binaries.

Guides

How to read a chmod number (755, 644, 777)

Questions

What does chmod 755 mean?: Owner can read, write and execute. Group and others can read and execute. Common for scripts and directories.
What does chmod 644 mean?: Owner can read and write. Everyone else can read. Common for ordinary files.
What permissions should an SSH key have?: 600 for the private key and 700 for the .ssh directory. OpenSSH refuses keys others can read.
What is the sticky bit?: On a directory, it stops users deleting files they do not own. /tmp is 1777.