fs-overlay/
            └── etc/
                ├── ssh/
                │   └── sshd_config      # SSH 主配置文件
                └── init.d/
                    ├── S40sshd_setup    # SSH 环境设置脚本

mkdir -p fs-overlay/etc/ssh
mkdir -p fs-overlay/etc/init.d

# OpenSSH精简配置 - 兼容嵌入式系统
Port 22
AddressFamily inet
ListenAddress 0.0.0.0

# 主机密钥路径
HostKey /etc/ssh/ssh_host_rsa_key
HostKey /etc/ssh/ssh_host_ecdsa_key
HostKey /etc/ssh/ssh_host_ed25519_key

# 认证设置
PermitRootLogin yes
PasswordAuthentication yes
PubkeyAuthentication yes
PermitEmptyPasswords no

# 禁用不支持的功能
# PrintLastLog no    # 注释掉，旧版本不支持
# UsePAM no          # 注释掉，Buildroot通常不启用PAM
ChallengeResponseAuthentication no
UsePrivilegeSeparation yes

# 日志
SyslogFacility AUTH
LogLevel INFO

# 客户端保活
ClientAliveInterval 30
ClientAliveCountMax 3

# 禁用不必要功能
X11Forwarding no
PrintMotd no

# 子系统
Subsystem sftp /usr/libexec/sftp-server

# 性能优化
UseDNS no
Compression delayed

vim  S40sshd_setup
chmod +x  S40sshd_setup

#!/bin/sh
# S40sshd_setup - 在SSH服务启动前设置环境

case "$1" in
  start)
    echo "Setting up SSH environment (before sshd starts)..."

    # 1. 创建必需目录（必须在ssh服务启动前完成）

    # 2. 检查主机密钥是否存在
    echo "Checking SSH host keys..."
    if [ ! -f /etc/ssh/ssh_host_rsa_key ]; then
        echo "ERROR: SSH host keys not found in /etc/ssh/"
        echo "Make sure 'install server keys' is enabled in Buildroot"
        # 不要尝试生成密钥，因为文件系统只读
    else
        echo "SSH host keys found, setting permissions..."
        # 设置正确的权限
        chmod 600 /etc/ssh/ssh_host_*_key 2>/dev/null || true
        chmod 644 /etc/ssh/ssh_host_*_key.pub 2>/dev/null || true
        chmod 755 /etc/ssh 2>/dev/null || true
    fi

    # 3. 确保运行时目录存在
    mkdir -p /var/run/sshd
    mkdir -p /var/lock/subsys

    echo "SSH environment setup complete."
    ;;
  stop)
    # 停止时无需特别操作
    ;;
  *)
    echo "Usage: $0 {start|stop}"
    exit 1
    ;;
esac

exit 0
~     

./build.sh rootfs
./build.sh firmware

检查密钥
ls -la /etc/ssh/
hexdump -C /etc/ssh/ssh_host_rsa_key | head -5