question regarding early ssh with kvm

question regarding early ssh with kvm

[Oliver Zemann]

Hi

I would like to run my centos with an encrypted hard drive without 
entering the password with vnc (as the connection is not encrypted). For 
that i followed the guide on 
http://roosbertl.blogspot.ch/2012/12/centos6-disk-encryption-with-remote.html

When i follow the tutorial in VirtualBox, i at least can see that i 
create a connection to the machine.
But on my productive server which runs in KVM, i even cant ping the machine.

Is there some way to print out debug messages (like "ip addr show") 
before the mount command has been executed? Maybe some kvm console 
driver where i can pipe messages to...?
Also, is virtio_net and virtio_pci enough to load?

I try to get that working for more than 10 days now, this is really 
driving me crazy.

Thanks in advance.

Oli

Re: question regarding early ssh with kvm

[Stefan Hajnoczi]

On Tue, Sep 17, 2013 at 09:27:24PM +0200, Oliver Zemann wrote:
> I would like to run my centos with an encrypted hard drive without
> entering the password with vnc (as the connection is not encrypted).
> For that i followed the guide on http://roosbertl.blogspot.ch/2012/12/centos6-disk-encryption-with-remote.html
> 
> When i follow the tutorial in VirtualBox, i at least can see that i
> create a connection to the machine.
> But on my productive server which runs in KVM, i even cant ping the machine.
> 
> Is there some way to print out debug messages (like "ip addr show")
> before the mount command has been executed? Maybe some kvm console
> driver where i can pipe messages to...?
> Also, is virtio_net and virtio_pci enough to load?
> 
> I try to get that working for more than 10 days now, this is really
> driving me crazy.

In a situation like this a serial console can be helpful.  Set the
kernel command-line to use the serial port (console=ttyS0) and make sure
the VM is configured with a serial port device.

This will allow you to follow the boot process.  If you need an
interactive prompt, check the distro initramfs scripts and set the
relevant debug options to get a shell prompt during the boot.

Stefan

Re: question regarding early ssh with kvm

[Oliver Zemann]

Hi Stefan

Thanks for your help.
I am able now to print some messages like lsmod, ip addr show etc.
I loaded virtio_net and virtio_pci, there are also a few more, but eth0 
is still unknown to the system.
Do i need any other module?

Regards,
Oli

Am 18.09.2013 10:14, schrieb Stefan Hajnoczi:
> On Tue, Sep 17, 2013 at 09:27:24PM +0200, Oliver Zemann wrote:
>> I would like to run my centos with an encrypted hard drive without
>> entering the password with vnc (as the connection is not encrypted).
>> For that i followed the guide on http://roosbertl.blogspot.ch/2012/12/centos6-disk-encryption-with-remote.html
>>
>> When i follow the tutorial in VirtualBox, i at least can see that i
>> create a connection to the machine.
>> But on my productive server which runs in KVM, i even cant ping the machine.
>>
>> Is there some way to print out debug messages (like "ip addr show")
>> before the mount command has been executed? Maybe some kvm console
>> driver where i can pipe messages to...?
>> Also, is virtio_net and virtio_pci enough to load?
>>
>> I try to get that working for more than 10 days now, this is really
>> driving me crazy.
> In a situation like this a serial console can be helpful.  Set the
> kernel command-line to use the serial port (console=ttyS0) and make sure
> the VM is configured with a serial port device.
>
> This will allow you to follow the boot process.  If you need an
> interactive prompt, check the distro initramfs scripts and set the
> relevant debug options to get a shell prompt during the boot.
>
> Stefan

Re: question regarding early ssh with kvm

[Stefan Hajnoczi]

On Wed, Sep 18, 2013 at 09:44:48PM +0200, Oliver Zemann wrote:
> I am able now to print some messages like lsmod, ip addr show etc.
> I loaded virtio_net and virtio_pci, there are also a few more, but
> eth0 is still unknown to the system.
> Do i need any other module?

Check that the virtio-net PCI adapter is present:

 $ grep 1af41000 /proc/bus/pci/devices

The output should print many fields and end with "virtio_pci" (the
driver that is bound to this device).

If you get no output from this grep command then your QEMU command-line
does not define a virtio-net PCI device.

If you get output but the last field is empty or "?" then you are
missing virtio kernel modules.  This can happen either because you
didn't compile them or because the udev device aliases file hasn't been
updated to autoload the right kernel module.

Stefan

Re: question regarding early ssh with kvm

[Oliver Zemann]

Hi Stefan

Everything looks as expected.
Even more wierd: when i execute the script 01remote-ssh.sh as stated in 
http://roosbertl.blogspot.ch/2012/12/centos6-disk-encryption-with-remote.html 
i can connect with ssh to that machine, so its not a kvm problem i guess.

Many thanks for your help.

Btw.: when running on centos and not knowing how to get a initramfs 
interactive shell, simply append "rdshell" to the kernel params (grub) 
and hit 2 times ctrl+c on the password prompt for the hdd/luks encryption.

Regards,
Oliver

Am 19.09.2013 13:40, schrieb Stefan Hajnoczi:
> On Wed, Sep 18, 2013 at 09:44:48PM +0200, Oliver Zemann wrote:
>> I am able now to print some messages like lsmod, ip addr show etc.
>> I loaded virtio_net and virtio_pci, there are also a few more, but
>> eth0 is still unknown to the system.
>> Do i need any other module?
> Check that the virtio-net PCI adapter is present:
>
>   $ grep 1af41000 /proc/bus/pci/devices
>
> The output should print many fields and end with "virtio_pci" (the
> driver that is bound to this device).
>
> If you get no output from this grep command then your QEMU command-line
> does not define a virtio-net PCI device.
>
> If you get output but the last field is empty or "?" then you are
> missing virtio kernel modules.  This can happen either because you
> didn't compile them or because the udev device aliases file hasn't been
> updated to autoload the right kernel module.
>
> Stefan