ubuntu DNS로 인해 apt-get install이 잘못되었습니다.

There are two parts to your question:

fixing temporary resolve messages

fixing the package management issues

Temporary resolve

It is likely that this issue is either:

temporary due to your Internet Service Provider not correctly forwarding internet naming (DNS) to either its or external DNS servers, or

due to a change in your network has similarly blocked this naming - for example, new router/modem, reconfiguring a switch with a new configuration.

Lets look at the possible DNS resolving issues.
First, temporarily add a known DNS server to your system.

echo "nameserver 8.8.8.8" | sudo tee /etc/resolv.conf > /dev/null

Then run  sudo apt-get update .
If this fixes your temporary resolving messages then either wait for 24 hours to see if your ISP fixes the issue for you (or just contact your ISP) - or you can permanently add a DNS server to your system:
　　 echo "nameserver 8.8.8.8" | sudo tee /etc/resolvconf/resolv.conf.d/base > /dev/null 8.8.8.8  is Google's own DNS server.
source
Another example DNS server you could use is  OpenDNS  - for example:

echo "nameserver 208.67.222.222" | sudo tee /etc/resolvconf/resolv.conf.d/base > /dev/null

package-management issues

In addition to the temporary resolve issues - you have a few package management issues that need to be corrected - I'm assuming you have tried recently to upgrade from one Ubuntu version to the next recommended version - in your case from Natty (11.04) to Oneiric (11.10)
Open a terminal and type

sudo nano /etc/apt/sources.list

Look for lines that have your a different distribution name in the list than you were expecting - in your case - you have upgraded to  oneiric  but you have another release name  natty
For example, look for lines that look like  deb http:/archive.canonical.com/ natty backports
Add a  #  to the beginning of the line to comment it out - for example #deb http:/archive.canonical.com/ natty backports
Save and re-run:

sudo apt-get update && sudo apt-get upgrade

You should not have any more release naming errors.
At the time of writing this, possible common  release names  include  lucid ,  maverick ,  natty ,  oneiric ,  precise  and  quantal