libvirt users - Aug 2014 - Re: username and passwd after create VM from XML dump

On Tue, Aug 5, 2014 at 6:33 PM, Eric Blake <eblake@redhat.com> wrote:
> On 08/05/2014 03:02 PM, Yuanzhen Gu wrote:
> > Good afternoon guys,
> >
> > I created the VM from XML dump,
> > # virsh create vm4.xml
> >
> > and # virsh list   I can see the VM running,
> > and I know the ip address for the VM,
> >
> > but how can I know the username and password to login the running VM,
> which
> > is created from XML dump?  is there any place to edit and add the
> username
> > and password in guest domain XML ?   thanks a lot!!
>
> Libvirt is only concerned with what virtual hardware you present to the
>
> guest, not with the OS running in that guest or what username/password
>
> combinations will let you log into that guest OS.  libguestfs may be
>
> able to do some introspection for learning usernames, and also has the
>
> ability to create guest clones where you control the usernames and
>
> passwords to be used in the new guest.
>
>
       Thanks!  so do you mean that I can use libvirt clone a new guest
with which I can give username and password?

>   But it is up to you to manage
>
> your VMs to where you know what username/password pairs are stored for a
>
> given guest image.
>
>
      but I've no idea where the username and passwd be stored, create it
with dumpXML of a VM, I've tried that original VM's username and passwd
via
ssh, but it didn't work.
>
> --
> Eric Blake   eblake redhat com    +1-919-301-3266
> Libvirt virtualization library http://libvirt.org
>
>

On 08/06/2014 11:11 AM, Yuanzhen Gu wrote:
>> Libvirt is only concerned with what virtual hardware you present to the
>>
>> guest, not with the OS running in that guest or what username/password
>>
>> combinations will let you log into that guest OS.  libguestfs may be
>>
>> able to do some introspection for learning usernames, and also has the
>>
>> ability to create guest clones where you control the usernames and
>>
>> passwords to be used in the new guest.
>>
>>
>        Thanks!  so do you mean that I can use libvirt clone a new guest
> with which I can give username and password?
Libvirt can just copy guest storage and hardware configuration.  If you
use only libvirt to do a guest clone, then the clone will have the same
OS credentials as the original.  That's probably not what you want.

You seem to be asking about libguestfs - but that's a higher-level
application than libvirt, so you may want to migrate your questions to
the libguestfs list.  http://libguestfs.org/virt-sysprep.1.html gives an
overview of the sort of things you can do when prepping a cloned system
via libguestfs, such as setting up a known account with a known password.

>       but I've no idea where the username and passwd be stored, create
it
> with dumpXML of a VM, I've tried that original VM's username and
passwd via
> ssh, but it didn't work.
Again, libvirt could care less what passwords your guest OS uses, as
passwords are not hardware, so dumpxml is unable to show you that
information(well, you COULD use libvirt's virDomainSetMetadata to store
custom XML that records that information, and then dumpxml would repeat
back the custom XML you associated with the guest - but again, that's
something you do as management, and not something libvirt tracks
natively).  Libguestfs knows how to introspect guest file systems, and
may help you create a new password, but if you were careless enough to
lose track of what password an existing guest was using, I seriously
doubt there is anything that we can do to help you recover that
password, at least if it was stored securely by the guest OS.

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org

On Wed, Aug 6, 2014 at 1:29 PM, Eric Blake <eblake@redhat.com> wrote:
> On 08/06/2014 11:11 AM, Yuanzhen Gu wrote:
>
> >> Libvirt is only concerned with what virtual hardware you present
to the
> >>
> >> guest, not with the OS running in that guest or what
username/password
> >>
> >> combinations will let you log into that guest OS.  libguestfs may
be
> >>
> >> able to do some introspection for learning usernames, and also has
the
> >>
> >> ability to create guest clones where you control the usernames and
> >>
> >> passwords to be used in the new guest.
> >>
> >>
> >        Thanks!  so do you mean that I can use libvirt clone a new
guest
> > with which I can give username and password?
>
> Libvirt can just copy guest storage and hardware configuration.  If you
> use only libvirt to do a guest clone, then the clone will have the same
> OS credentials as the original.  That's probably not what you want.
>
> You seem to be asking about libguestfs - but that's a higher-level
> application than libvirt, so you may want to migrate your questions to
> the libguestfs list.  http://libguestfs.org/virt-sysprep.1.html gives an
> overview of the sort of things you can do when prepping a cloned system
> via libguestfs, such as setting up a known account with a known password.
>
>
> >       but I've no idea where the username and passwd be stored,
create it
> > with dumpXML of a VM, I've tried that original VM's username
and passwd
> via
> > ssh, but it didn't work.
>
> Again, libvirt could care less what passwords your guest OS uses, as
> passwords are not hardware, so dumpxml is unable to show you that
> information(well, you COULD use libvirt's virDomainSetMetadata to store
> custom XML that records that information, and then dumpxml would repeat
> back the custom XML you associated with the guest - but again, that's
> something you do as management, and not something libvirt tracks
> natively).  Libguestfs knows how to introspect guest file systems, and
> may help you create a new password, but if you were careless enough to
> lose track of what password an existing guest was using, I seriously
> doubt there is anything that we can do to help you recover that
> password, at least if it was stored securely by the guest OS.
>
    I see, thank you so much Eric!
    Just one more question to make me clear in this point, so if I install
an application in the guest, and make a dmup XML, then     create a new
guest using that configured dump XML file, the new guest should also have
that application installed?  and the username and password of the new guest
should be the same as the previous guest?   thanks a lot!
>
>
 --
> Eric Blake   eblake redhat com    +1-919-301-3266
> Libvirt virtualization library http://libvirt.org
>
>