How to Change Sudo Password Remembering Time in Ubuntu

When You use 'sudo' command it will ask for password in First time and will remember password for 15 minutes. It is a security hole for sensitive systems.
You can change sudo Password Remembering Time in Ubuntu .

Open a terminal and type
$ sudo visudo

In Ubuntu, visudo uses nano text editor, and what it does is edit the / etc / sudoers.tmp

Check for the line as shown below

Defaults        env_reset


Change it to

Defaults        env_reset , timestamp_timeout = X

Where X is the time that we remember the sudo password, if we put 0 (zero) that we always get the request.

Finally to save the changes, press Ctrl + X and said yes.

How to Recover Ubuntu after a Partial Upgrade

If your Ubuntu machine is nor working properly after a partial upgrade and have a have broken the system dependencies tree, You can recover it by using a  simple command that reinstalls all the installed packages and reconfigures them automatically.This will take a long time to complete.

$sudo dpkg-reconfigure -phigh -a

You can try the following command first

$ sudo apt-get install -f

How to setup Google Public DNS in Ubuntu 9.10 Karmic Koala

DNS (Domain Name Server) is basically a system to convert domain names into IP addresses. Domain names are easier to understand, memorize and write for humans while computers only use IP addresses to communicate.

In most of the  case, Internet Service Providers  providing the DNS servers to the customer. User can change it, the  reasons to switch to other DNS servers for performance, privacy and censorship. Most of the people using OpenDNS as the first alternative, But Now Google Public DNS is available and the performance is much better.

Now How to set up Google Public DNS in Ubuntu

Select System-->Preferences-->Network Connections

Select  the type of connection you have. For this example, we will use ‘Wired’.

Under ‘Wired’, highlight ‘Auto etho’ and click on ‘Edit’.

Now,  Inside 'Editing Auto etho' window, click on ‘IPv4 Settings’ tab. and select 'Automatic (DHCP) address only'

Put these nameserver addresses as your ‘DNS Servers’:8.8.8.8, 8.8.4.4

Click ‘OK’ and reboot your machine.

NOTE:

For avoiding  your settings get revoked after reboots, you may need to make the following changes via the command line:

$ sudo cp /etc/resolv.conf /etc/resolv.conf.auto
$ gksudo gedit /etc/dhcp3/dhclient.conf
# append the following line to the document
prepend domain-name-servers 8.8.8.8, 8.8.4.4;
# save and exit
$ sudo ifdown eth0 && sudo ifup eth0