无法通过 SSH 连接到运行 dropbear sshd 的 QEMU 虚拟机 [英] Cannot SSH into QEMU virtual machine running dropbear sshd
问题描述
我已经建立了一个模拟 vexpress-a9 机器的 QEMU 虚拟机.我使用 buildroot 创建了 initrd 系统，并且使用了 buildroot 下载的 codesourcery 交叉编译器作为编译 Linux 内核的设置的一部分.这就是我调用 qemu 的方式
I have set up a QEMU virtual machine emulating the vexpress-a9 machine. I've used buildroot to create the initrd system and I've used the codesourcery cross-compiler that buildroot downloads as part of it's setup to compile the Linux Kernel. This is how I invoke qemu
qemu-system-arm -m 512 -M vexpress-a9-dtb linux-4.4.192/arch/arm/boot/dts/vexpress-v2p-ca9.dtb-内核linux-4.4.192/arch/arm/boot/zImage-initrd buildroot/output/images/rootfs.cpio-附加控制台=ttyAMA0，ip=dhcp"-net nic,model=lan9118-net 用户,hostfwd=tcp::2222-:22-nographic
它启动得很好.与网络相关的启动消息表明网络已初始化并且 dropbear sshd 已启动并运行:
It boots just fine. Network related boot messages that tell that the network has been initialized and dropbear sshd was brought up and running:
启动网络:OK启动 dropbear sshd: random: dropbear: 未初始化的 urandom 读取(读取 32 个字节，1 位可用熵)好的
但是eth0 接口必须手动分配一个IP.我在与我的 Linux 主机相同的子网中为它分配了一个未使用的 C 类地址，如下所示:
however the eth0 interface has to be assigned an IP manually. I assign it an unused class C address in the same subnet as my Linux host like so:
# ifconfig eth0 192.168.160.150 upsmsc911x 4e000000.ethernet eth0:SMSC911x/921x 标识为 0xa12a0000，IRQ:31
所以 ifconfig 现在显示:
# 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)
netstat 告诉我我们正在监听端口 22:
netstat tells me that we are listening on port 22:
# 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 到本地主机:
I can even ssh into localhost like so:
# ssh root@127.0.0.1
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
root@127.0.0.1's password:
random: dropbear: uninitialized urandom read (32 bytes read, 26 bits of entropy available)
而在主机上，这是我尝试从 linux 主机通过 SSH 连接到此 VM 时所看到的:
whereas from the host this is what I see when I try to SSH into this VM from the linux host:
$ ssh -vvv root@192.168.160.150
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
我很乐意就此提供一些建议，因为我找不到其他可以尝试的方法
I would be pleased to have some pointers about this as I cannot find what else can be tried
更新 1: 在配置 buildroot 时包含 dhcpd.现在无论我是使用 dropbear 还是 openssh，日志消息都会出现直到
UPDATE 1: Included dhcpd while configuring buildroot. Now irrespective of whether I use dropbear or openssh, the log messages appear until
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)
此时它只是停止，我看不到登录提示.删除 dhcpd 并使用 dropbear 或 openssh 后，我可以再次看到登录提示(意味着所有 init 脚本运行完成)，但再次没有任何类型的连接.我不明白为什么dhcpd世界上会认为我们没有载体(当它能够枚举和识别模拟的NIC卡时)
at which point it just kind of stops and I cannot see the login prompt. Upon removing dhcpd and using either dropbear or openssh, I can see the login prompt again (meaning all the init scripts run to completion) but again no connectivity of any kind. I can't understand why in the world does dhcpd thinks we have no carrier (when it is able to enumerate and identify the emulated NIC card)
UPDATE2:我尝试手动调用 udhcpc 以通过 DHCP 获取地址，但它确实获取了地址
UPDATE2: I've tried invoking udhcpc manually to obtain an address via DHCP and it does get an address
# 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
但是主机仍然无法访问该机器.我是否需要从主机添加到此 VM 的手动路由?如果是，我该怎么做?QEMU 是否在主机上创建了一个虚拟接口(就像工作站一样)?
The machine is still however inaccessible from the host. Do I need to add a manual route to this VM from the host? If yes how do I do that? Does QEMU create a virtual interface on the host (like workstation does)?
推荐答案
昨天我花了几个小时尝试使用 的不同选项(即 ，但最后有用的是这个选项: -net、-netdev)qemu-system-arm-nic user,hostfwd=::2222-:22 我从 已删除功能页面(查看替换 -redir 选项).我还必须在主机的 SSH 配置文件中添加这 3 行:/etc/ssh/ssh_config
I spent hours yesterday trying different options (i.e. -net, -netdev) with qemu-system-arm, but finally what worked was this one option: -nic user,hostfwd=::2222-:22 Which I learned from the list of removed features page (look at replacement of -redir option). I also had to add these 3 lines in my host's SSH config file: /etc/ssh/ssh_config
Host localhost
PreferredAuthentications=password
PubkeyAuthentication=no
这篇关于无法通过 SSH 连接到运行 dropbear sshd 的 QEMU 虚拟机的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！
