解决树莓派apt-get upgrade出现的apt-get upgrade问题

执行sudo apt-get upgrade出现以下错误：

E: The value '\stable' is invalid for APT::Default-Release as such a release is not available in the sources

解决办法：

1、

# sudo grep -ri stable /etc

出现以下信息：

/etc/dhcpcd.conf:# Generate Stable Private IPv6 Addresses instead of hardware based ones
/etc/staff-group-for-usr-local:release wheezy+1 as stable, all packages that need it check that this
/etc/apparmor.d/abstractions/lightdm_chromium-browser:  /opt/google/chrome-stable/google-chrome-stabl              e Cx -> chromium,
/etc/apparmor.d/abstractions/lightdm_chromium-browser:  /opt/google/chrome-unstable/google-chrome-uns              table Cx -> chromium,
/etc/apt/apt.conf.d/10defaultRelease:APT::Default-release \"stable";

2、

找到以下类似信息

/etc/apt/apt.conf.d/10defaultRelease:APT::Default-release \"stable";

修改该文件

sudo nano /etc/apt/apt.conf.d/10defaultRelease

将stable替换为jessie

3、保存修改