Почему я не могу обновить? [Дубликат]

Я запускаю lsb_release -a

Выход:

No LSB modules are available.
Distributor ID: Ubuntu
Description:    Ubuntu 12.04.4 LTS
Release:    12.04
Codename:   precise  

Я запускаю: nano /etc/apt/sources.list

Выход:

deb mirror://mirrors.ubuntu.com/mirrors.txt precise main universe
deb mirror://mirrors.ubuntu.com/mirrors.txt precise main-updates universe multiverse
deb mirror://mirrors.ubuntu.com/mirrors.txt precise main-backports universe multiverse
deb mirror://mirrors.ubuntu.com/mirrors.txt precise main-security universe multiverse

Я запускаю sudo apt-get update

Outuput:

Hit http://ftp.oleane.net/ubuntu/ precise Release.gpg
Hit http://ftp.oleane.net/ubuntu/ precise Release
Hit http://ftp.oleane.net/ubuntu/ precise/main i386 Packages
Hit http://ftp.oleane.net/ubuntu/ precise/universe i386 Packages
W: Failed to fetch mirror://mirrors.ubuntu.com/mirrors.txt/dists/precise/Release  Unable to find expected entry 'main-updates/binary-i386/Packages' in Release file (Wrong sources.list entry or malformed file)

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