3步实现SSH免密登录Linux服务器

准备工作

确保本地机器和目标Linux服务器均已安装OpenSSH服务。通过以下命令检查SSH服务状态：

systemctl status sshd

若未安装，使用对应包管理器安装：

# Ubuntu/Debian
sudo apt install openssh-server
# CentOS/RHEL
sudo yum install openssh-server

生成密钥对

在本地机器生成RSA密钥对（默认存放在~/.ssh/目录）：

ssh-keygen -t rsa -b 4096

连续回车三次（不设置密码短语），生成id_rsa（私钥）和id_rsa.pub（公钥）文件。

上传公钥到服务器

使用ssh-copy-id工具自动上传公钥：

ssh-copy-id username@server_ip

若未安装该工具，可手动操作：

cat ~/.ssh/id_rsa.pub | ssh username@server_ip "mkdir -p ~/.ssh && cat >> ~/.ssh/authorized_keys"

设置权限

确保服务器端权限正确：

chmod 700 ~/.ssh
chmod 600 ~/.ssh/authorized_keys

验证免密登录

直接使用SSH命令连接服务器：

ssh username@server_ip

若无需输入密码即登录成功，表示配置完成。

故障排查

若登录失败，检查服务器SSH配置：

sudo vi /etc/ssh/sshd_config

确认以下参数：

PubkeyAuthentication yes
AuthorizedKeysFile .ssh/authorized_keys
PasswordAuthentication no  # 可选：禁用密码登录提升安全性

修改后重启服务：

sudo systemctl restart sshd

高级配置

多服务器管理时，可编辑本地~/.ssh/config文件：

Host alias1
    HostName server1_ip
    User username1
    IdentityFile ~/.ssh/id_rsa

Host alias2
    HostName server2_ip
    User username2
    IdentityFile ~/.ssh/id_rsa

之后可通过别名连接：

ssh alias1

安全建议

私钥文件权限必须为600
生产环境建议使用ED25519算法：ssh-keygen -t ed25519
定期轮换密钥对
使用ssh-agent管理密钥密码短语

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