我在 ARM 设备（Zynq Mini-ITX 开发板）上安装了 Linaro Ubuntu。这是我的
# lsb_release -a
输出：
Distributor ID: Ubuntu
Description: Ubuntu 12.04.5 LTS
Release: 12.04
Codename: precise
我想运行 do-release-upgrade 但是它说：
Error during update
A problem occurred during the update. This is usually some sort of
network problem, please check your network connection and retry.
W:Failed to fetch http://ports.ubuntu.com/dists/trusty/Release Unable
to find expected entry 'main/binary-armel/Packages' in Release file
(Wrong sources.list entry or malformed file)
, W:Failed to fetch
http://ports.ubuntu.com/dists/trusty-security/Release Unable to find
expected entry 'main/binary-armel/Packages' in Release file (Wrong
sources.list entry or malformed file)
, W:Failed to fetch
http://ports.ubuntu.com/dists/trusty-updates/Release Unable to find
expected entry 'main/binary-armel/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.
apt-get update 也不起作用：
Err http://us.archive.ubuntu.com precise/main armel Packages
404 Not Found [IP: 91.189.91.13 80]
Err http://us.archive.ubuntu.com precise/universe armel Packages
404 Not Found [IP: 91.189.91.13 80]
W: Failed to fetch http://us.archive.ubuntu.com/ubuntu/dists/precise/main/binary-armel/Packages 404 Not Found [IP: 91.189.91.13 80]
我试过俄罗斯和美国镜像，但没什么区别。我的网络连接没问题。我想我必须以某种方式修复我的 sources.list 文件。我试过在http://repogen.simplylinux.ch/但什么都没起作用。我读到我必须使用主 Ubuntu 服务器进行 apt-get 更新，而不是它的美国镜像。有人能告诉我怎么做吗？
我需要做什么？