[lxc-devel] [PATCH 1/4] Honor network type and link from lxc-create -f

Dwight Engen dwight.engen at oracle.com
Thu Oct 11 15:54:52 UTC 2012


On Thu, 11 Oct 2012 10:10:03 -0500
Serge Hallyn <serge.hallyn at canonical.com> wrote:

> Quoting Dwight Engen (dwight.engen at oracle.com):
> > Make the oracle template honor the lxc.network.type and
> > lxc.network.link configuration items if a "base" configuration file
> > is passed to lxc-create. If no configuration file is passed, the
> > template falls back to the default name created by libvirt.
> > 
> > Signed-off-by: Dwight Engen <dwight.engen at oracle.com>
> > ---
> >  templates/lxc-oracle.in |   16 ++++++++++++----
> >  1 files changed, 12 insertions(+), 4 deletions(-)
> > 
> > diff --git a/templates/lxc-oracle.in b/templates/lxc-oracle.in
> > index ba62f8f..2d62396 100644
> > --- a/templates/lxc-oracle.in
> > +++ b/templates/lxc-oracle.in
> > @@ -27,10 +27,6 @@
> >  # Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
> > 02111-1307 USA #
> >  
> > -# use virbr0 that is setup by default by libvirtd
> > -lxc_network_type=veth
> > -lxc_network_link=virbr0
> > -
> >  die()
> >  {
> >      echo "failed: $1"
> > @@ -250,6 +246,18 @@ container_config_create()
> >  		      head -1 |awk '{print $2}' | cut -c1-10 |\
> >  		      sed 's/\(..\)/\1:/g; s/.$//'`"
> >      mkdir -p $cfg_dir || die "unable to create config dir $cfg_dir"
> > +
> > +    # see if the network settings are specified in the file thats
> > handed to us
> > +    lxc_network_type=`grep '^lxc.network.type' $cfg_dir/config |
> > awk -F'[= \t]+' '{ print $2 }'`
> > +    if [ -z "$lxc_network_type" ]; then
> > +	lxc_network_type="veth"
> > +    fi
> > +
> > +    lxc_network_link=`grep '^lxc.network.link' $cfg_dir/config |
> > awk -F'[= \t]+' '{ print $2 }'`
> > +    if [ -z "$lxc_network_link" ]; then
> > +	lxc_network_link="virbr0"
> > +    fi
> > +
> 
> Hi,
> 
> the creator might want to put other things in the initial config,
> such as lxc.cgroup.devices entries.

Yes that is what was bothering me, does the user/host config know
better which devices should be imported to the container or the
template? I guess we're okay since you must be root on the host to
start them, so root just has to know that those devices make sense for
the container. So instead of removing the config, I guess I'll just
have a little function that adds config keys one at a time, checking to
see that it's not already there, so that way anything can be specified
in the copied in config and the template won't override it. Sound
reasonable?

> When you do 'lxc-create -t TEMPLATE -n p1 -f CONFIG", lxc-create will
> copy CONFIG to /var/lib/lxc/p1/config.  I think it would be better for
> your template to not remove the config copied over by lxc-create.  So
> don't do the above steps.  If you want the default to be to use
> virbr0, just check whether 'lxc.network.type' is not in the config
> yet, and if it is not then set 
> 
> lxc_network_type=veth
> lxc_network_link=virbr0
> 
> as you were before.  (I'm sure you know this, but to be clear, if
> there is no 'lxc.network.type' at all then the container will share
> the host's network, and if it is 'lxc.network.type = empty' then it
> will have a private netns with only loopback.  So you can pick what
> you want for a default, but this way the distro, by setting a default
> /etc/lxc/lxc.conf, can easily choose a default bridge for
> lxc.network.link while the template can choose what to do if nothing
> is specified.

I do remember seeing that, but you're right that I wasn't thinking
of that use case (shared network by not having lxc.network.type) since
my goal was to keep the 'default' containers created fairly isolated,
but still update-able through the network.

This also gets back to the fact that lxc-create in git doesn't
copy /etc/lxc/lxc.conf if no -f is specified, so I guess that only
works on Ubuntu now? I'd like to add the 'distro' lxc.conf file and
have the rpm .spec package it, but it won't do much good without the
part in lxc-create :( Doing so would actually obviate the need for the
template to have a "host default" for networking since it would just
honor /etc/lxc/lxc.conf, making the template more 'host distro'
agnostic. I'm happy to add the bits for this to lxc-create that Ubuntu
already has, and add an lxc.conf to the source tree if you want.




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