解决在 Docker 中换源后 No system certificates available. Try installing ca-certificates 问题

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参考
先用原本的仓库安装 ca-certificates (若先换了源, 就会找不到安装包):

apt-get update
apt-get -y install ca-certificates

然后再换源和更新:

sed -i "s@http://.*archive.ubuntu.com@https://mirrors.tuna.tsinghua.edu.cn@g" /etc/apt/sources.list
sed -i "s@http://.*security.ubuntu.com@https://mirrors.tuna.tsinghua.edu.cn@g" /etc/apt/sources.list
apt-get update