ubuntu 软件包管理配置文件

　　ubuntu是用apt管理软件包的，软件下载及更新源配置在哪里呢？软件更新出问题，怎么解决呢？

• 系统软件源配置
  • /etc/apt/sources.list
• 普通软件源配置
  • /etc/apt/sources.list.d目录下
  • 例如ros的配置文件：ros-latest.list，还有vscode的配置文件也是在这个目录下

　　更多的相关文件：

　　/etc/apt/sources.list

　　Locations to fetch packages from. Configuration Item: Dir::Etc::SourceList.

/etc/apt/sources.list.d/
File fragments for locations to fetch packages from. Configuration Item: Dir::Etc::SourceParts.

/etc/apt/apt.conf
APT configuration file. Configuration Item: Dir::Etc::Main.

/etc/apt/apt.conf.d/
APT configuration file fragments. Configuration Item: Dir::Etc::Parts.

/etc/apt/preferences
Version preferences file. This is where you would specify "pinning", i.e. a preference to get certain packages from a separate source or from a different version of a distribution.
Configuration Item: Dir::Etc::Preferences.

/etc/apt/preferences.d/
File fragments for the version preferences. Configuration Item: Dir::Etc::PreferencesParts.

/var/cache/apt/archives/
Storage area for retrieved package files. Configuration Item: Dir::Cache::Archives.

/var/cache/apt/archives/partial/
Storage area for package files in transit. Configuration Item: Dir::Cache::Archives (partial will be implicitly appended)

/var/lib/apt/lists/
Storage area for state information for each package resource specified in sources.list(5) Configuration Item: Dir::State::Lists.

/var/lib/apt/lists/partial/
Storage area for state information in transit. Configuration Item: Dir::State::Lists (partial will be implicitly appended)