Birmingham mumbai

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It probably goes without saying, but the 
rm
 command can be extremely dangerous. 
If you're logged in as 
root
 or using 
sudo
 while using 
rm
, you can easily destroy 
your entire installed system if you're not careful. 
DO NOT run this command
, but as 
a hypothetical example, the following command (while seemingly innocent at first 
glance) will likely completely destroy your entire filesystem:
sudo rm -r / home/dscully
At this point, we understand how to add and remove users. In the next section, we'll 
look deeper into passwords. 
Understanding the /etc/passwd and /etc/
shadow files
Now that we know how to create (and delete) user accounts on our server, we 
are well on our way to being able to manage our users. But where exactly is this 
information stored? We know that users store their personal files in 
/home
, but is 
there some kind of database somewhere that keeps track of which user accounts are 
on our system? Actually, user account information is stored in two special text files:
• 
/etc/passwd
• 
/etc/shadow
You can display the contents of each of those two files with the following commands. 
Note that any user can look at the contents of 
/etc/passwd
, while only 
root
 has 
access to 
/etc/shadow
:
cat /etc/passwd 
sudo cat /etc/shadow
Go ahead and take a look at these two files (just don't make any changes), and I will 
help you understand them.
Notice the typo: I accidentally typed a space after the first forward 
slash. I literally accidentally told my system to remove the contents 
of the entire filesystem. If that command was executed, the server 
probably wouldn't even boot the next time we attempted to start it. 
All user and program data would be wiped out. If there was ever 
any single reason for us to be protective over the 
root
 account, the 
rm
 command is certainly it!

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Managing Users and Permissions