i just can't get it to my head, right now i am learning about umask, could someone tell me a better way to understand how it function

thanks

A umask is something you can apply as a mount option to volumes in the fstab. If you set the umask to 002 as an option in an fstab entry, the files will be read/write by all. Useful for mounting external devices or network devices as user read/write when they usually default to root only read/write.

The term umask however is more general and can be applied to many things.

Well, umask also applies to creating new files. Think of the umask setting as turning off the permissions it lists. If you're like me, and have a problem thinking that using a value means the opposite will come out, then think of it using subtraction. In other words, remember that all files can have a permission value of 777. When you create a file, you subtract the umask from 777.

So, if you have a umask of 022 (which is very common), then a new file created will have permissions of 777 - 022 = 755 (owner has all perms, group and other have read and execute perms).

One gotcha is this: the application that creates the file sometimes does not give the execute permission by default. For instance, if you used the touch command with a umask of 022, the file you create would be 777 - 111 (touch does not give execute) - 022 = 644 (owner has read & write, everybody else only has read).

Clear as mud?