Cannot SSH into QEMU virtual machine running dropbear sshd
我已经设置了一个模拟vexpress-a9机器的QEMU虚拟机。我使用buildroot来创建initrd系统，并且使用了buildroot下载的代码源交叉编译器作为编译Linux内核的一部分。这就是我调用qemu
的方式
-dtb linux-4.4.192/arch/arm/boot/dts/vexpress-v2p-ca9.dtb
-kernel linux-4.4.192/arch/arm/boot/zImage
-initrd buildroot/output/images/rootfs.cpio
-append"console=ttyAMA0,ip=dhcp"
-net nic,model=lan9118
-net user,hostfwd=tcp::2222-:22
-nographic
它启动很好。与网络相关的引导消息，表明网络已经初始化，并且dropbear sshd已启动并正在运行：
Starting dropbear sshd: random: dropbear: uninitialized urandom read (32 bytes read, 1 bits of entropy available)
OK
但是
smsc911x 4e000000.ethernet eth0: SMSC911x/921x identified at 0xa12a0000, IRQ: 31
所以
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 | # ifconfig eth0 Link encap:Ethernet HWaddr 52:54:00:12:34:56 inet addr:192.168.160.150 Bcast:192.168.160.255 Mask:255.255.255.0 UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:0 errors:0 dropped:0 overruns:0 frame:0 TX packets:0 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:0 (0.0 B) TX bytes:0 (0.0 B) Interrupt:31 lo Link encap:Local Loopback inet addr:127.0.0.1 Mask:255.0.0.0 UP LOOPBACK RUNNING MTU:65536 Metric:1 RX packets:0 errors:0 dropped:0 overruns:0 frame:0 TX packets:0 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1 RX bytes:0 (0.0 B) TX bytes:0 (0.0 B) |
1 2 3 4 | # netstat -tln Active Internet connections (only servers) Proto Recv-Q Send-Q Local Address Foreign Address State tcp 0 0 0.0.0.0:22 0.0.0.0:* LISTEN |
我什至可以像这样SSH到localhost：
1 2 3 4 5 6 7 8 9 10 11 | # ssh [email protected] random: ssh: uninitialized urandom read (32 bytes read, 24 bits of entropy available) random: dropbear: uninitialized urandom read (32 bytes read, 24 bits of entropy available) random: dropbear: uninitialized urandom read (32 bytes read, 24 bits of entropy available) random: dropbear: uninitialized urandom read (32 bytes read, 24 bits of entropy available) Host '127.0.0.1' is not in the trusted hosts file. (ecdsa-sha2-nistp256 fingerprint sha1!! de:cf:f8:b3:ac:4d:96:47:22:d7:76:a1:ea:11:3d:bc:ec:c6:71:9a) Do you want to continue connecting? (y/n) y [email protected]'s password: random: dropbear: uninitialized urandom read (32 bytes read, 26 bits of entropy available) |
而当我尝试从linux主机通过SSH进入此VM时，从主机上看到的是这句话：
1 2 3 4 5 6 7 8 9 | $ ssh -vvv [email protected] OpenSSH_7.4p1 Debian-10+deb9u7, OpenSSL 1.0.2s 28 May 2019 debug1: Reading configuration data /etc/ssh/ssh_config debug1: /etc/ssh/ssh_config line 19: Applying options for * debug2: resolving"192.168.160.150" port 22 debug2: ssh_connect_direct: needpriv 0 debug1: Connecting to 192.168.160.150 [192.168.160.150] port 22. debug1: connect to address 192.168.160.150 port 22: No route to host ssh: connect to host 192.168.160.150 port 22: No route to host |
我很高兴能对此提出一些建议，因为我找不到其他可以尝试的方法
更新1：配置buildroot时包含dhcpd。现在，无论我使用dropbear还是openssh，日志消息都会一直显示到
1 2 3 4 5 6 7 | Starting dhcpcd... no interfaces have a carrier <--- the problem forked to background, child pid 746 smsc911x 4e000000.ethernet eth0: SMSC911x/921x identified at 0xa12a0000, IRQ: 31 Starting dropbear sshd: random: dropbear: uninitialized urandom read (32 bytes read, 2 bits of entropy available) OK random: dhcpcd: uninitialized urandom read (120 bytes read, 2 bits of entropy available) |
这时只是停止，我看不到登录提示。删除
UPDATE2：我尝试手动调用
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 | # udhcpc -S -a100 udhcpc: started, v1.31.0 udhcpc: sending discover udhcpc: sending select for 10.0.2.15 udhcpc: lease of 10.0.2.15 obtained, lease time 86400 deleting routers adding dns 10.0.2.3 # ifconfig eth0 Link encap:Ethernet HWaddr 52:54:00:12:34:56 inet addr:10.0.2.15 Bcast:10.0.2.255 Mask:255.255.255.0 UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:4 errors:0 dropped:0 overruns:0 frame:0 TX packets:5 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:2360 (2.3 KiB) TX bytes:1428 (1.3 KiB) Interrupt:31 |
但是仍然无法从主机访问计算机。我是否需要从主机向该VM添加手动路由？如果是，我该怎么做？ QEMU是否在主机上创建虚拟接口(就像工作站一样)？
如果您正在使用QEMU的"用户"模式网络，则尝试在主机的网络中为访客分配IP地址是错误的。用户模式网络使用自己的DHCP服务器创建了一个模拟的网络-您可以在https://wiki.qemu.org/Documentation/Networking#User_Networking_.28SLIRP.29
上看到其示意图。
默认情况下，来宾所在的网络是10.0.2.x，但是您可以使用命令行参数对其进行更改。
配置来宾的最简单方法是让它运行DHCP客户端，该客户端应该能够找到QEMU提供的内置DHCP服务器，并以此方式在仿真网络上获取IP地址。
关于用户模式网络的重要一点是，它通常不允许您直接从主机连接到来宾VM。连接到它的唯一方法是，如果您的QEMU命令行指定了要从主机转发到来宾的特定端口，如果这样做，则可以连接到在命令行转发选项中指定的主机IP地址和端口。并将其转发到仿真网络上来宾的IP地址和端口。
如果这还不够，并且您需要VM出现在桥接到主机网络的真实虚拟接口上，则应停止使用用户模式网络，而应查看TAP网络选项。但是，TAP的设置更为复杂。
昨天我花了几个小时尝试使用
1 2 3 | Host localhost PreferredAuthentications=password PubkeyAuthentication=no |