[Libguestfs] Notes on building libguestfs in a systemd-nspawn container

[Daniel P. Berrange]

On Thu, Jan 30, 2014 at 04:34:04PM +0530, Kashyap Chamarthy wrote:
> On 01/30/2014 03:58 PM, Richard W.M. Jones wrote:
> >>> - `make -k check` is still running as I write this, albeit
> >>>    a bit slow.
> >>
> >> This just finished (in the container):
> >>
> >>     [. . .]
> >>     grep -v -E '^(examples|gnulib|perl/(blib|examples)|po-docs|tests)/' | \
> >>     grep -v -E '/((guestfs|rc)_protocol\.c)$' | \
> >>     LC_ALL=C sort > po/POTFILES
> >>     cd .; \
> >>     find builder mllib resize sparsify sysprep -name '*.ml' | \
> >>     LC_ALL=C sort > po/POTFILES-ml
> >>     make[1]: Leaving directory `/root/libguestfs'
> >>     make: *** [check-recursive] Error 1
> >>       GEN      public-submodule-commit
> >>     make: Target `check' not remade because of errors.
> >>
> >>     real    474m53.630s
> >>     user    325m54.254s
> >>     sys     205m58.032s
> >>
> >>     -bash-4.2# git log | head -1
> >>     commit c841d08d7084db69e81614d54423686cf0566ad6
> >>
> >>
> >> Again, for comparison, `make -k check` on _host_:
> >>
> >>     real    63m1.078s
> >>     user    54m39.393s
> >>     sys     12m8.130s
> > 
> > Is KVM available in the container?  I've never tried that actually ..
> 
> No it isn't (as Dan noted in his next thread)
> 
> =========
> -bash-4.2# file /dev/kvm
> /dev/kvm: ERROR: cannot open `/dev/kvm' (No such file or directory)
> =========
> -bash-4.2# virt-host-validate
>   QEMU: Checking for hardware virtualization
>      : PASS
>   QEMU: Checking for device /dev/kvm
>      : FAIL (Check that the 'kvm-intel' or 'kvm-amd' modules are loaded
> & the BIOS has enabled virtualization)
>   QEMU: Checking for device /dev/vhost-net
>      : WARN (Load the 'vhost_net' module to improve performance of
> virtio networking)
>   QEMU: Checking for device /dev/net/tun
>      : FAIL (Load the 'tun' module to enable networking for QEMU guests)
>    LXC: Checking for Linux >= 2.6.26
>      : PASS
> =========
> 
> Despite reading from the `systemd-nspawn` man page:
> 
>  ". . .kernel modules may not be loaded from within the container."
> 
> I purposefully tried from inside the container:

With container based virt there is only one kernel image, so any
modules you want must be loaded in the host. Libvirt "passthrough"
of char/block devices simply involves libvirt doing mknod in the
/dev tmpfs it sets up. The container itself is blocked from doing
any 'mknod' calls since that'd be a security risk. Hence you must
list any desired device nodes in the XML config.

Daniel
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