[Qemu-discuss] failed to connect to ssh-agent when attach a ssh json backing image

[Han Han]

Hi all,
I tried to attach a ssh json backing image but failed:
# qemu-img create -f qcow2 -b 'json:{"file.driver":"ssh", 
"file.host":"10.66.4.129", "file.path":"/tmp/ssh", "file.user":"root", 
"file.port":22, "file.host_key_check":"no"}' /var/lib/libvirt/images/ssh.img
Formatting '/var/lib/libvirt/images/ssh.img', fmt=qcow2 size=104857600 
backing_file=json:{"file.driver":"ssh",, "file.host":"10.66.4.129",, 
"file.path":"/tmp/ssh",, "file.user":"root",, "file.port":22,, 
"file.host_key_check":"no"} encryption=off cluster_size=65536 
lazy_refcounts=off refcount_bits=16

# virsh start V
Domain V started

# virsh attach-disk V /var/lib/libvirt/images/ssh.img vdb --subdriver qcow2 
error: Failed to attach disk
error: internal error: unable to execute QEMU command '__com.redhat_drive_add': 
Device 'drive-virtio-disk1' could not be initialized

In VM log:
2016-08-18 06:18:02.572+0000: starting up libvirt version: 2.0.0, package: 
5.el7 (Red Hat, Inc. <http://bugzilla.redhat.com/bugzilla>, 
2016-08-10-12:57:06, x86-019.build.eng.bos.redhat.com), qemu version: 2.6.0 
(qemu-kvm-rhev-2.6.0-21.el7), hostname: lab.test.me
LC_ALL=C PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin 
QEMU_AUDIO_DRV=spice /usr/libexec/qemu-kvm -name guest=V,debug-threads=on -S 
-object 
secret,id=masterKey0,format=raw,file=/var/lib/libvirt/qemu/domain-33-V/master-key.aes
 -machine pc-i440fx-rhel7.3.0,accel=kvm,usb=off,vmport=off -cpu SandyBridge -m 
1024 -realtime mlock=off -smp 1,sockets=1,cores=1,threads=1 -uuid 
a2deb379-2c56-4adb-b278-021462eed0bd -no-user-config -nodefaults -chardev 
socket,id=charmonitor,path=/var/lib/libvirt/qemu/domain-33-V/monitor.sock,server,nowait
 -mon chardev=charmonitor,id=monitor,mode=control -rtc base=utc,driftfix=slew 
-global kvm-pit.lost_tick_policy=discard -no-hpet -no-shutdown -global 
PIIX4_PM.disable_s3=1 -global PIIX4_PM.disable_s4=1 -boot strict=on -device 
ich9-usb-ehci1,id=usb,bus=pci.0,addr=0x6.0x7 -device 
ich9-usb-uhci1,masterbus=usb.0,firstport=0,bus=pci.0,multifunction=on,addr=0x6 
-device ich9-usb-uhci2,masterbus=usb.0,firstport=2,bus=pci.0,addr=0x6.0x1 
-device ich9-usb-uhci3,masterbus=usb.0,firstport=4,bus=pci.0,addr=0x6.0x2 
-device virtio-serial-pci,id=virtio-serial0,bus=pci.0,addr=0x5 -drive 
file=/var/lib/libvirt/images/V.qcow2,format=qcow2,if=none,id=drive-virtio-disk0 
-device 
virtio-blk-pci,scsi=off,bus=pci.0,addr=0x7,drive=drive-virtio-disk0,id=virtio-disk0,bootindex=1
 -netdev tap,fd=29,id=hostnet0,vhost=on,vhostfd=31 -device 
virtio-net-pci,netdev=hostnet0,id=net0,mac=52:54:00:23:4f:f8,bus=pci.0,addr=0x3 
-chardev pty,id=charserial0 -device isa-serial,chardev=charserial0,id=serial0 
-chardev 
socket,id=charchannel0,path=/var/lib/libvirt/qemu/channel/target/domain-33-V/org.qemu.guest_agent.0,server,nowait
 -device 
virtserialport,bus=virtio-serial0.0,nr=1,chardev=charchannel0,id=channel0,name=org.qemu.guest_agent.0
 -chardev spicevmc,id=charchannel1,name=vdagent -device 
virtserialport,bus=virtio-serial0.0,nr=2,chardev=charchannel1,id=channel1,name=com.redhat.spice.0
 -device usb-tablet,id=input0,bus=usb.0,port=1 -spice 
port=5903,addr=127.0.0.1,disable-ticketing,image-compression=off,seamless-migration=on
 -device 
qxl-vga,id=video0,ram_size=67108864,vram_size=67108864,vram64_size_mb=0,vgamem_mb=16,bus=pci.0,addr=0x2
 -device intel-hda,id=sound0,bus=pci.0,addr=0x4 -device 
hda-duplex,id=sound0-codec0,bus=sound0.0,cad=0 -chardev 
spicevmc,id=charredir0,name=usbredir -device 
usb-redir,chardev=charredir0,id=redir0,bus=usb.0,port=2 -chardev 
spicevmc,id=charredir1,name=usbredir -device 
usb-redir,chardev=charredir1,id=redir1,bus=usb.0,port=3 -device 
virtio-balloon-pci,id=balloon0,bus=pci.0,addr=0x8 -msg timestamp=on
char device redirected to /dev/pts/20 (label charserial0)
Could not open backing file: failed to connect to ssh-agent: no auth sock 
variable (libssh2 error code: -39)

So is it a qemu bug? Or something I did wrongly? Thks