[libvirt-users] Broken OS when booting rootfs from 9p share

Mon Mar 2 13:13:16 UTC 2015

Finally got it working by setting user root as qemu user and
disabling clearing of capabilities.

Olivier 

On 2015-02-26 17:49,
Olivier Mauras wrote: 

> On 2015-02-26 17:05, Kashyap Chamarthy wrote:

> 
>> On Tue, Feb 24, 2015 at 11:56:50PM +0100, Olivier Mauras
wrote:
>> 
>>> On Tue, 2015-02-24 at 16:05 -0500, Laine Stump wrote:

>>> 
>>>> On 02/24/2015 03:37 PM, Olivier Mauras wrote: 
>>>> 
>>>>>>
Hello, I've been trying to boot a VM with the rootfs being a 9P share
from the host. The VM OS is centos 7. The OS boots but no services can
work and it appears that the authentication system is broken. Now the
funny thing is that booting the same OS on the same 9P share manually
with Qemu works as expected with a fully functionnal OS... So I'm
wondering what could libvirt do that render the OS on the share broken -
Something with rights ? Selinux is disabled on the host, and accessmode
to the share is set to passthrough in both cases. Here's my working Qemu
line: qemu -kernel
/srv/overlay/kernels/grsec-3.14.33-101/vmlinuz-3.14.33-101.el6.x86_64
-initrd
/srv/overlay/kernels/grsec-3.14.33-101/initramfs-3.14.33-101.el6.x86_64.img
-fsdev local,id=r,path=/srv/overlay/run/irc,security_model=passthrough
-device virtio-9p-pci,fsdev=r,mount_tag=root -nographic -m 256M -machine
pc-i440fx-2.1,accel=kvm -netdev tap,id=net0 -device
virtio-net,netdev=net0,mac=52:54:00:12:36:34 -smp 1,sockets=1,cores=1
-append 'root=virtfs:root rootflags=trans=virtio,version=9p2000.u ro
rootfstype=9p console=ttyS0' And here my libvirt VM
config:ircffbd32eb-a693-eadd-8923-18de801374722621442621441hvm/srv/overlay/kernels/grsec-3.14.33-101/vmlinuz-3.14.33-101.el6.x86_64/srv/overlay/kernels/grsec-3.14.33-101/initramfs-3.14.33-101.el6.x86_64.imgroot=virtfs:root
rootflags=trans=virtio,version=9p2000.u ro
rootfstype=9pdestroyrestartrestart/usr/bin/qemu-system-x86_64 My libvirt
version is 1.2.9, and qemu is 2.1.2. Thanks for your help, Olivier
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>>>>> So I
updated libvirt to 1.2.12 and qemu to 2.1.3 and it still gives me the
exact same behaviour ... Could it be that the share was created with an
old version of virt-manager redenring in old/broken XML? From Qemu
config example i don't see how my XML could be incorrect. Any idea
?
>>>> I know nothing about the 9p filesystem, but since you have a qemu
commandline that works and a libvirt config that doesn't, the next
logical step would be to provide the non-working qemu commandline
generated by libvirt. You can find this at the end of the log file
/var/log/libvirt/qemu/irc.log.
>>> Here it is... A bit more complex :)
LC_ALL=C PATH=/sbin:/usr/sbin:/bin:/usr/bin QEMU_AUDIO_DRV=none
/usr/bin/qemu-system-x86_64 -name irc -S -machine
pc-i440fx-2.1,accel=kvm,usb=off -m 256 -realtime mlock=off -smp
1,sockets=1,cores=1,threads=1 -uuid ffbd32eb-a693-eadd-8923-18de80137472
-no-user-config -nodefaults -chardev
socket,id=charmonitor,path=/var/lib/libvirt/qemu/irc.monitor,server,nowait
-mon chardev=charmonitor,id=monitor,mode=control -rtc base=utc
-no-shutdown -no-acpi -boot strict=on -kernel
/srv/overlay/kernels/grsec-3.14.33-101/vmlinuz-3.14.33-101.el6.x86_64
-initrd
/srv/overlay/kernels/grsec-3.14.33-101/initramfs-3.14.33-101.el6.x86_64.img
-append root=virtfs:root rootflags=trans=virtio,version=9p2000.u rw
rootfstype=9p -device piix3-usb-uhci,id=usb,bus=pci.0,addr=0x1.0x2
-fsdev
local,security_model=passthrough,id=fsdev-fs0,path=/srv/overlay/run/irc
-device
virtio-9p-pci,id=fs0,fsdev=fsdev-fs0,mount_tag=root,bus=pci.0,addr=0x5
-netdev tap,fd=27,id=hostnet0,vhost=on,vhostfd=28 -device
virtio-net-pci,netdev=hostnet0,id=net0,mac=52:54:00:00:10:10,bus=pci.0,addr=0x3
-chardev pty,id=charserial0 -device
isa-serial,chardev=charserial0,id=serial0 -vnc 127.0.0.1:3 -device
cirrus-vga,id=video0,bus=pci.0,addr=0x2 -device
virtio-balloon-pci,id=balloon0,bus=pci.0,addr=0x4 -msg timestamp=on
>>

>> Maybe you can try enabling Debug logs/filters in libvirt
>> 
>>
http://wiki.libvirt.org/page/DebugLogs
>> 
>> and see if that helps you
narrow down?
> 
> #!/bin/bash
> LC_ALL=C
PATH=/sbin:/usr/sbin:/bin:/usr/bin QEMU_AUDIO_DRV=none
/usr/bin/qemu-system-x86_64 -name irc -machine pc-i440fx-2.1,accel=kvm
-m 256 -smp 1,sockets=1,cores=1,threads=1 
> -no-user-config 
> -chardev
socket,id=charmonitor,path=/var/lib/libvirt/qemu/irc.monitor,server,nowait
-mon chardev=charmonitor,id=monitor,mode=control -rtc base=utc -boot
strict=on 
> -kernel
/srv/overlay/kernels/grsec-3.14.33-101/vmlinuz-3.14.33-101.el6.x86_64 
>
-initrd
/srv/overlay/kernels/grsec-3.14.33-101/initramfs-3.14.33-101.el6.x86_64.img

> -append 'root=virtfs:root rootflags=trans=virtio,version=9p2000.u rw
rootfstype=9p console=ttyS0' 
> -fsdev
local,security_model=passthrough,id=fsdev-fs0,path=/srv/overlay/run/irc
-nographic 
> -device
virtio-9p-pci,id=fs0,fsdev=fsdev-fs0,mount_tag=root,bus=pci.0,addr=0x5

> -chardev stdio,id=charserial0 -device
isa-serial,chardev=charserial0,id=serial0 -device
cirrus-vga,id=video0,bus=pci.0,addr=0x3 -device
virtio-balloon-pci,id=balloon0,bus=pci.0,addr=0x4 -msg timestamp=on
> 
>
This gives me the same result as my first qemu command. Seems that
-nodefaults gives me non booted state VM.

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[2]
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