ubutnu20.04更新源报错：E:...签名不再生效

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一、问题

当执行sudo apt update的时候出现如下错误：

二、解决方案

1.修改软件源列表​

根据Ubuntu版本选择对应命令（ 以下是Ubuntu 20.04 (ROS Noetic) 清华源 ）

sudo sh -c 'echo "deb https://mirrors.tuna.tsinghua.edu.cn/ros/ubuntu focal main" > /etc/apt/sources.list.d/ros-latest.list'

2.更换清华源

清华大学开源软件镜像站

修改sources.list

sudo gedit /etc/apt/sources.list

更换清华源（和步骤一对应）

# 默认注释了源码镜像以提高 apt update 速度，如有需要可自行取消注释
deb https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ focal main restricted universe multiverse
# deb-src https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ focal main restricted universe multiverse
deb https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ focal-updates main restricted universe multiverse
# deb-src https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ focal-updates main restricted universe multiverse
deb https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ focal-backports main restricted universe multiverse
# deb-src https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ focal-backports main restricted universe multiverse# 以下安全更新软件源包含了官方源与镜像站配置，如有需要可自行修改注释切换
deb http://security.ubuntu.com/ubuntu/ focal-security main restricted universe multiverse
# deb-src http://security.ubuntu.com/ubuntu/ focal-security main restricted universe multiverse

3.添加并信任GPG密钥​

sudo apt-key adv --keyserver 'hkp://keyserver.ubuntu.com:80' --recv-key C1CF6E31E6BADE8868B172B4F42ED6FBAB17C654

若密钥失效，改用官方密钥备份（我没用到）

sudo curl -sSL https://raw.githubusercontent.com/ros/rosdistro/master/ros.key -o /usr/share/keyrings/ros-archive-keyring.gpg

4.更新软件列表​

sudo apt update