我总是收到错误：
W: Failed to fetch http://ftp2.de.debian.org/debian/dists/stable-updates /Release Expected entry »maindeb/source/Sources« couldn't be found in release file (wrong entry in sources.list or wrongly formed file).
（我的德语翻译，我不知道使用英语作为系统语言是否会得到完全相同的错误）
这是我的来源列表：
# standard
deb http://ftp2.de.debian.org/debian/ stable main
deb-src http://ftp2.de.debian.org/debian/ stable main
# security
deb http://security.debian.org/ stable/updates main
deb-src http://security.debian.org/ stable/updates main
# wheezy-updates, previously known as 'volatile'
# deb http://ftp2.de.debian.org/debian/ stable-updates main
deb-src http://ftp2.de.debian.org/debian/ stable-updates maindeb
deb http://ftp2.de.debian.org/debian/ experimental main
deb http://ftp.debian.org/debian sid main
答案1
正如输出所示，您的 maindeb 有问题：
deb-src http://ftp2.de.debian.org/debian/ stable-updates 曼德布
删除仅保留的 deb main，然后重试。