Tag Archives: linux commands

how to login as root in ubuntu 10.04

login as root

By default you can’t login as root in ubuntu 10.04 or other linux distribution due to the security policy of linux.Suppose you have logged in as root in ubuntu and by mistake you did something wrong then your system may be crash.But administrative power is required in some cases such as in installing some programs to solve file permission problem while working on file system.That’s why there is a simple solution and is sudo command.hence you can do administrative task or run administrative commands followed by sudo.Hence in this method you will have to work in command line interface.So in the case if you don’t know much more about ubuntu commands OR you feel irritating in doing some administrative task fr0m command line then you can enable the root login fr0m the login menu  and run as a root.

Hence It is very simple to enable root logging in graphical or GUI mode, just follow these simple steps –

step1. Open the bash terminal.


step2. Type the command  sudo passwd root.First it will ask for the user password.Enter your current-user session password and and hit enter.

ubuntuuser@ubuntuuser-desktop:~$ sudo passwd root

[sudo] password for ubuntuuser:

step3. Then it will ask for new password.Enter a new password twice.This is the password you will use this in future for logging as root.

Enter new UNIX password:

Retype new UNIX password:

passwd: password updated successfully


step4. To check whether it is working or not just logout fr0m the current session.At login prompt,choose other as a user account.Next, in the place of username write root and the password you just defined in the above step.

step5. that’s all..I hope your work is done.

NOTE : If you logged in as root then you must be careful about the each activities.After finishing the administrative task you should return to the normal mode.

You may like this post : A simple tutorial to learn- how to secure from internet threats.

What is sudo in Ubuntu?

Sudo commands in linuxIn early days it was difficult to manage the permissions for different users in a multiuser operating system that may be a client or server;suppose every user has a power of a superuser or root then any one of them may be misused the system either intentionally(If the user is smart) or ignorantly(If the user is a beginner one).Hence the simple solution of this problem is to limit the power for every users according to their need so that they can do simple tasks normally but in case of any administrative task root power is granted for small period(usually five minutes)by using the sudo commands.In sudo su stands for superuser and do means do(as usual).Hence sudo is mostly used by a permitted user for taking the permission to execute some commands as a another user or superuser, according to the information specified in sudoers file.Suppose the user that is invoking a command using the sudo power, is root then there is no need to enter user password.By default authentication is required and the user password is required; the user may use the sudo power again for short period of time(5-15min).So sudo is very useful in finishing some administrative task by a simple user.Now we are going to learn something more about the sudo commands.

Syntax of the sudo commands :

It is very simple..just use the word sudo before the actual command and hit enter.Then it will ask for the users password ..enter the password after the authorization process the commands will execute.e.g I am trying to execute commands1(installing a package using apt-get).

user840@user840-desktop:~$ sudo commands1
[sudo] password for user840:
Reading package lists… Done
Building dependency tree
Reading state information… Done

….and so on the execution will complete.

Options in SUDO :

-A : Using this option the another helper program(It may be in graphical format) is called and executed to read the password of the user and output the user password to the canonical output.

-u user : this option tells the sudo to run the target command as a user instead of root(which is default case).You may use UID rather than username by using UID followed by ‘#’.i.e #uid.
-a : It is used by the sudo to use the special authentication type for the validation of the user according to the permission settings stored in /etc/login.conf.
This option is is used only in the system having the support with BSD authentication mechanism.

-b : Specifying -b(background) with the sudo command simply means to order the sudo that “run the target command in background”.

-p prompt : By using -p (prompt) one can easily customize the password prompt.So using some ‘%’ escapes(e.g %H,%h,%p) you may use any other prompt rather then the default one.

Although there are many other options available but you can easily find out in your bash shell.just type info sudo and hit enter.

Environment Variables :

here are the some environment variables used by the sudo.

USER : Set to the current user.By default its value is equal to root if -u option is not specified.

SUDO_UID : user ID of the user who used the sudo.

SUDO_USER : Set to the login of the permitted user who is using sudo.
Go to your bash terminal for the details about the more environmental variables(info sudo OR man -k sudo OR help sudo).

Credit : Todd C. Miller