What do the following SUDO-Commands mean and do?

Question

Hey Everybody,
I did google these two commands but I cannot find a straight answer which is understandable for me. Can someone please explain to me in plain English what they do?
1. "sudo chmod -RN ~"
2. "sudo chown -R `id -un` ~"
My second question is: After I have executed these 2 commands, will there be a problem or danger to my system if I won't boot up off the Leopard DVD and click the "Reset" button in the "Reset Home Directory Permissions and ACLs" section? Because this reset seems not possible on my machine.
Thank you very much for your answers!
AirMcEnroe

Answer 1

I'll start off by asking if you have a problem that you are trying to solve, or if you are just having fun with Google? The sudo command is a very dangerous command, and using the -R option allows the computer to multiply your mistakes with amazing speed.
I did google these two commands but I cannot find a straight answer which is understandable for me. Can someone please explain to me in plain English what they do?
1. "sudo chmod -RN ~"
sudo says run the following command as if you were the super user (the all powerful). It will prompt for your password (assuming you are an 'admin' user). You will see nothing while typing the password.
chmod is used to change file permissions (see "man chmod").
The tilda ~ says start with your home directory.
-R says recursively process every file and directory under the specified starting directory (in this case you specified ~ your home directory).
-N says remove any Access Control Lists (ACL) found.
Not sure why you want to do this. It seems like a very big hammer and some of those ACLs may be service a valuable function, such as protecting you from shooting yourself in the foot, or enabling specific needed permissions on newly created files, etc...
And if you happen to fumble finger entering the starting directory ~, you could destroy ACLs outside of your home directory tree and destroy critical OS ACLs.
Make sure you have a very good full system backup before you take aim at your foot.
2. "sudo chown -R `id -un` ~"
chown changes the ownership of files and directories.
-R says recursively process every file and directory under the specified starting directory (in this case you specified ~ your home directory).
`id -un` obtains your short username, the `...` says substitute the output from id -un onto the chown command line.
So this command is going to walk your home directory tree and change the ownership of every file and directory it finds and force you to be the owner.
Again a very big hammer, and one that if you specify the wrong starting directory will turn your Mac into a paper weight. Make sure you have a very good full backup before you start.
My second question is: After I have executed these 2 commands, will there be a problem or danger to my system if I won't boot up off the Leopard DVD and click the "Reset" button in the "Reset Home Directory Permissions and ACLs" section? Because this reset seems not possible on my machine.
By the way, Terminal, Unix, X11, and command line command, ssh, rsync, etc... questions are best asked in the Mac OS X Technologies > Unix Forum
<http://discussions.apple.com/forum.jspa?forumID=735>