Question: I get the file parmission on my folder, so I run the following command

```
sudo chmod 777 -R /*

```

and get some error line. 
then I try to login as root user by the following command

```
sudo su

```

get this error like as 

```
supravat@supravat:~$ sudo su
sudo: must be setuid root

```

Then I research regarding this error. and followed some source but error is still present.
<http://www.linuxquestions.org/questions/linux-software-2/sudo-must-be-setuid-root-854117/>

When I run following commend as like 

```
chown root:root /usr/bin/sudo

```

Get this mesasage..

```
chown: changing ownership of '/usr/bin/sudo' : read-only file system

```

Please help me.

Answer: 
The command you run: `sudo chmod 777 -R /*` or `sudo chmod 777 -R /` changes the permission of ALL file in your system to `777`: read, write and executable for everyone. That's a major security risk. You opened your system for everyone. **NEVER run this command.** Everyone who gives you that command wants your system to be insecure. It's peanuts to get root access on such a system.

I recommend you to reinstall your whole system. You could try to set the permissions back to the original ones, but you can never be sure. I see only one option: Reinstallation.
sudo checks that its permissions are 4755 (rwsr-xr-x). After giving world-writable permissions to every file as you have, the entire concept of becoming superuser to do privileged work is defeated, as anyone and everyone who logs on your system can do everything and anything superuser can.

After a

> 
> `sudo chmod 777 -R /*`
> 
> 
> 

only a full reformat and reinstall makes the box safe again. I really don't know of a list of system files with default out-of-the-box permissions.

Even if you find this, you also need a list of system file checksums, and to verify the checksum program itself to ensure your method of ensuring the authenticity of files wasn't compromised.

Probably it is simpler to reformat the drive and reinstall Linux.

Hope this helps.