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.
your this command is the most bad approach i have ever made

```
sudo chmod 777 -R /*

```

actually you have give all red,write and execution permission.
never do such work i think u should learn, study and understand Linux 
solve of your problem is 

```
chmod 4755 /usr/bin/sudo

```

then run

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

```

and after this you will find some other file having same problem 
so better you check all the file permission from a well running system and apply them to your filesystem.