网络访问失败导致 Docker GPG 密钥下载失败，进而 apt 无法验证 Docker 仓库，最终安装失败。

install -m 0755 -d /etc/apt/keyrings
curl -fsSL https://download.docker.com/linux/ubuntu/gpg | gpg --dearmor -o /etc/apt/keyrings/docker.gpg
chmod a+r /etc/apt/keyrings/docker.gpg
echo \
"deb [arch="$(dpkg --print-architecture)" signed-by=/etc/apt/keyrings/docker.gpg] https://download.docker.com/linux/ubuntu \
"$(. /etc/os-release && echo "$VERSION_CODENAME")" stable" | \
tee /etc/apt/sources.list.d/docker.list > /dev/null
apt update
apt install -y docker-ce docker-ce-cli containerd.io docker-compose-plugin

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解决方法

1. 清理旧的错误配置

rm -rf /etc/apt/keyrings/docker.gpg
rm -rf /etc/apt/sources.list.d/docker.list

2. 重新下载 Docker 密钥（国内可用，不会被重置）

curl -fsSL https://mirrors.aliyun.com/docker-ce/linux/ubuntu/gpg | gpg --dearmor -o /etc/apt/keyrings/docker.gpg
chmod a+r /etc/apt/keyrings/docker.gpg

3. 添加阿里云 Docker 软件源（稳定可用）

echo \
"deb [arch=$(dpkg --print-architecture) signed-by=/etc/apt/keyrings/docker.gpg] https://mirrors.aliyun.com/docker-ce/linux/ubuntu \
$(. /etc/os-release && echo "$VERSION_CODENAME") stable" | \
tee /etc/apt/sources.list.d/docker.list > /dev/null