[Libguestfs] Name resolution not working inside virt-customize

[Daniel P. Berrange]

On Tue, Mar 10, 2015 at 09:12:12PM +0000, Richard W.M. Jones wrote:
> On Tue, Mar 10, 2015 at 04:41:22PM -0400, Lee Revell wrote:
> > Hi!
> > 
> > I am trying to use virt-customize to add packages to an image.
> > However it seems that there is a problem where a resolv.conf is not
> > being installed and thus package installation fails.
> > 
> > The command is:
> > 
> > virt-customize -v -x -a trusty-server-cloudimg-amd64-disk1.img
> > --run-command "host openstack.org"
> >
> > I am having a hard time gathering complete output as the command
> > seems to corrupt my terminal somehow but I think the relevant lines
> > may be:
> > 
> > [   3.0] Running: host openstack.org
> > running command:
> > exec >>'/tmp/builder.log' 2>&1
> > 
> > 
> > host openstack.org
> > 
> > libguestfs: trace: sh "exec >>'/tmp/builder.log' 2>&1\n\n\nhost
> > openstack.org\n"
> > guestfsd: main_loop: new request, len 0x60
> > mount --bind /dev /sysroot/dev
> > mount --bind /dev/pts /sysroot/dev/pts
> > mount: mount point /sysroot/dev/pts does not exist
> > mount --bind /proc /sysroot/proc
> > mount --bind /sys/fs/selinux /sysroot/selinux
> > mount: mount point /sysroot/selinux does not exist
> > mount --bind /sys /sysroot/sys
> > mount --bind /sys/fs/selinux /sysroot/sys/fs/selinux
> > mount: mount point /sysroot/sys/fs/selinux does not exist
> > renaming /sysroot/etc/resolv.conf to /sysroot/etc/g1fbx1fs
> > cp /etc/resolv.conf /sysroot/etc/resolv.conf
> > cp: cannot stat '/etc/resolv.conf': No such file or directory
> > /bin/sh -c exec >>'/tmp/builder.log' 2>&1
> > 
> > 
> > host openstack.org
> > 
> > And the command fails due to the missing resolv.conf.
> > 
> > I am using version 1.28.6 build from source on ubuntu 14.04. The
> > same image file listed above works perfectly when launched as an
> > openstack instance.
> 
> I'm afraid our handling of /etc/resolv.conf inside the chroot is a
> large (and continuing) source of problems.  Currently this code is
> run:
> 
> https://github.com/libguestfs/libguestfs/blob/master/daemon/command.c#L148
> 
> There are a couple of thing you could do:
> 
>  - Don't rely too heavily on name resolution.
> 
>  - Use --firstboot* scripts instead, since they genuinely run in guest
>    context, and should therefore work more like you expect.
> 
> (and I guess a third one .. suggest a better approach to resolv.conf
> handling).

We can finally use overlayfs now it is merged

 # cat /etc/resolv.conf
 nameserver 192.168.1.254
 # mkdir /mnt/{overlay,empty,custometc}
 # mount -t overlay overlay -o lowerdir=/etc,upperdir=/mnt/overlay,workdir=/mnt/empty /mnt/custometc
 # echo "nameserver 192.168.1.1" > /mnt/custometc/resolv.conf
 # cat /mnt/custom/etcresolv.conf
 nameserver 192.168.1.1
 # cat /etc/resolv.conf
 nameserver 192.168.1.254

Regards,
Daniel
-- 
|: http://berrange.com      -o-    http://www.flickr.com/photos/dberrange/ :|
|: http://libvirt.org              -o-             http://virt-manager.org :|
|: http://autobuild.org       -o-         http://search.cpan.org/~danberr/ :|
|: http://entangle-photo.org       -o-       http://live.gnome.org/gtk-vnc :|