Passwordless login (ssh)

If u want to login without passwords from one system to another

the ssh service should be installed on both systems

sudo apt-get install openssh-server opensssh-client

Identify the system which should be server which one should client 

On the server system 

skx@lappy:~$ ssh-keygen -t rsa

Generating public/private rsa key pair.

Enter file in which to save the key (/home/skx/.ssh/id_rsa): 

Enter passphrase (empty for no passphrase): 

Enter same passphrase again: 

Your identification has been saved in /home/skx/.ssh/id_rsa.

Your public key has been saved in /home/skx/.ssh/id_rsa.pub.

Then copy th public key to client system make sure you full permissions to .ssh folder

ssh-copy-id -i ~/.ssh/id_rsa.pub username@mystery

Changing the screen resolution ubuntu 12.04 

If your monitor is not detecting the desired in the gui mode

You need to create xorg.conf file under /etc/X11 directory

cd /etc/X11

touch xorg.conf

Add the display modes to /etc/X11/xorg.conf

If you don’t have a xorg.conf, then you can use the following as a basis. You need to replace the entries with the names Modeline, Driver and Modes with the correct entries for your system. Depending on your hardware, you may need additional entries, for example if your system has more than one graphic chip.

Section “Monitor”
Identifier “Monitor0”
Modeline “1280x1024_60.00” 109.00 1280 1368 1496 1712 1024 1027 1034 1063 -hsync +vsync
Modeline “1024x768_60.00” 63.50 1024 1072 1176 1328 768 771 775 798 -hsync +vsync
EndSection
Section “Screen”
Identifier “Screen0”
Device “Card0”
Monitor “Monitor0”
SubSection “Display”
Modes “1280x1024_60.00” “1024x768_60.00”
EndSubSection
EndSection
Section “Device”
Identifier “Card0”
Driver “intel”
EndSection

If you don’t know the name of the video driver that your system is using then you may get the name as follows (if you have an intel graphic chip, the driver name is just “intel”):
lshw -class display | grep “driver”

The modelines can be generated with cvt:

Changing Passwords in ubuntu 12.04

If you want to change the password for any user account you can just give

kiran@localhost:#passwd “username”

kiran@localhost:#sudo passwd “username”

If you are getting  Authentication Manipulation error then you do not have privileges to change. You must do it at as a root user

By default Ubuntu wont create a root passord, you can set the root password 

sudo password root

then

Switch to root user

sudo bash

sudo -s

su -

If the root password is aleady changed or you forgot your root password then reboot your machine and enter into recovery mode , Or use a Ubuntu live cd 

1. When you get the grub menu appears, select option with recover as shown in figures.

Boot into the recovery mode , and then select drop into root shell prompt

Mount the filesystem into read write mode 

root@localhost$:mount -o rw,remount /

root@localhost$:sudo passwd root

root@localhost$:passwd “username”

Different desktop environments

If you are not comfortable with the default  unity desktop environment , You can try other desktop environments

And also if you system is old and doesn’t support high end graphics then you can try light weight desktop environments (XFCE and LXDE) as they wont use up too much ram 

1.XFCE

http://www.xfce.org/

sudo apt-get install xubuntu-desktop

2.LXDE

http://lxde.org/

sudo apt-get install lxde

3.Gnome 3

Last but not the least If you are not a keyboard person and heavily dependent on Mouse you can use Gnome 3

sudo add-apt-repository ppa:gnome3-team/gnome3

sudo apt-get install gnome-shell