Calculate Unix file permissions by clicking checkboxes or entering an octal value. Get symbolic and octal notation instantly.
Unix and Linux systems control access to files using a permission system. Every file and directory has three sets of permissions — one for the owner, one for the group, and one for everyone else. Each set has three possible permissions: read, write, and execute.
Permissions are represented in two ways. Symbolic notation uses letters like rwxr-xr-x. Octal notation uses three digits like 755 where each digit represents the sum of the permission values for that entity. Read is worth 4, write is worth 2, and execute is worth 1.
755 is the most common permission for directories and executable files. It means the owner can read, write and execute while group and others can only read and execute. 644 is standard for regular files where the owner can read and write but everyone else can only read. 600 is used for private files like SSH keys where only the owner can read and write.
Use the chmod command in the terminal. For example chmod 755 myfile sets the permissions to rwxr-xr-x. Use chmod -R to apply permissions recursively to all files in a directory.
For directories, execute permission means the ability to enter the directory and access its contents. Without execute permission you cannot cd into a directory or access files inside it even if you have read permission. Read permission on a directory lets you list its contents with ls.
755 gives the owner full permissions and gives group and others read and execute only. 777 gives everyone full permissions including write. You should avoid 777 in production because it lets any user on the system modify your files.
For most web server setups, directories should be 755 and files should be 644. This lets the web server read everything while preventing other users from modifying your files. Configuration files with sensitive data like passwords should be 600 so only the owner can read them.