установка git в ubuntu 12.10 [дубликат]

Я не могу установить git в моей системе ubuntu 12.10. Я выполнил-

sudo add-apt-repository ppa:git-core/ppa
sudo apt-get update
sudo apt-get install git-core

sudo apt-get update выдает ошибку-

Err http://security.ubuntu.com quantal-security/main amd64 Packages
  404  Not Found
Err http://security.ubuntu.com quantal-security/restricted amd64 Packages
  404  Not Found
Err http://security.ubuntu.com quantal-security/universe amd64 Packages
  404  Not Found
Err http://security.ubuntu.com quantal-security/multiverse amd64 Packages
  404  Not Found

Err http://archive.ubuntu.com quantal-updates/main amd64 Packages
  404  Not Found
Err http://archive.ubuntu.com quantal-updates/restricted amd64 Packages
  404  Not Found
Err http://archive.ubuntu.com quantal-updates/universe amd64 Packages
  404  Not Found
Err http://archive.ubuntu.com quantal-updates/multiverse amd64 Packages
  404  Not Found

Err http://archive.ubuntu.com quantal/main amd64 Packages
  404  Not Found
Err http://archive.ubuntu.com quantal/restricted amd64 Packages
  404  Not Found
Err http://archive.ubuntu.com quantal/universe amd64 Packages
  404  Not Found
Err http://archive.ubuntu.com quantal/multiverse amd64 Packages
  404  Not Found

Затем некоторые не смогли получить ошибки и, наконец ,-

E: Some index files failed to download. They have been ignored, or old ones used instead.

Когда я запустил sudo apt-get install git , Я получаю-

Building dependency tree       
Reading state information... Done
The following extra packages will be installed:
  git-man liberror-perl
Suggested packages:
  git-daemon-run git-daemon-sysvinit git-doc git-el git-arch git-cvs git-svn
  git-email git-gui gitk gitweb
The following NEW packages will be installed:
  git git-man liberror-perl
0 upgraded, 3 newly installed, 0 to remove and 0 not upgraded.
Need to get 6,800 kB/6,824 kB of archives.
After this operation, 15.3 MB of additional disk space will be used.
Do you want to continue [Y/n]? y
WARNING: The following packages cannot be authenticated!
  liberror-perl git-man git
Install these packages without verification [y/N]? y
Err http://archive.ubuntu.com/ubuntu/ quantal/main git-man all 1:1.7.10.4-1ubuntu1
  404  Not Found
Err http://archive.ubuntu.com/ubuntu/ quantal/main git amd64 1:1.7.10.4-1ubuntu1
  404  Not Found
Failed to fetch http://archive.ubuntu.com/ubuntu/pool/main/g/git/git-man_1.7.10.4-1ubuntu1_all.deb  404  Not Found
Failed to fetch http://archive.ubuntu.com/ubuntu/pool/main/g/git/git_1.7.10.4-1ubuntu1_amd64.deb  404  Not Found
E: Unable to fetch some archives, maybe run apt-get update or try with --fix-missing?

Я только что установил ubuntu, и это первая попытка установки. Пожалуйста помоги.