[lxc-devel] [PATCH] lxc-create: conside create succeed when container is already created

[Serge Hallyn]

Quoting Qiang Huang (h.huangqiang at huawei.com):
> On 2013/9/17 21:41, Serge Hallyn wrote:
> > Quoting Qiang Huang (h.huangqiang at huawei.com):
> >> On 2013/9/17 11:27, Serge Hallyn wrote:
> >>> Quoting Qiang Huang (h.huangqiang at huawei.com):
> >>>> On 2013/9/16 12:23, Stéphane Graber wrote:
> >>>>> On Mon, Sep 16, 2013 at 11:37:02AM +0800, Qiang Huang wrote:
> >>>>>> Sometimes we use:
> >>>>>> lxc-create -n xxx -f config
> >>>>>> to copy config to the default lxcpath with the rootfs already
> >>>>>> exist.
> >>>>>> But we will get error right now, so fix this.
> >>>>>
> >>>>> Hmm, I'm not sure I understand.
> >>>>>
> >>>>> Running "lxc-create -n xxx -f config" when xxx already exists is an
> >>>>> error and should return an error code so the current code seems
> >>>>> perfectly right to me.
> >>>>
> >>>> Well, it did works this way in the former lxc_create version.
> >>>>
> >>>> We used to use LXC this way:
> >>>> - We made a template(rootfs, config and fstab) manually.
> >>>
> >>> >From here, can you just write a script 'lxc-homebrew' which
> >>> copies the rootfs+config+fstab into place, and call
> >>>
> >>> 	lxc-create -t homebrew -n c1
> >>>
> >>> ?
> >>>
> >>> If you want to just copy the stuff in by hand, you can
> >>> do that.  You don't *have* to run lxc-create if you've done
> >>> everything by hand.
> >>
> >> OK, thanks Serge.
> >>
> >> So we are still not supposed to use lxc-create without -t option?
> > 
> > I just don't see the point, and I worry that people using the
> > common case will end up accidentally deleting existing container
> > data.
> > 
> > Well, the current code says
> > 
> >         /* container is already created if we have a config and rootfs.path is accessible */
> >         if (lxcapi_is_defined(c) && c->lxc_conf && c->lxc_conf->rootfs.path && access(c->lxc_conf->rootfs.path, F_OK) == 0)
> >                 goto out;
> > 
> > Maybe what we want to do is add a '&& access(c->configfile, F_OK) to that
> > test?  I think that would give you what you want, and I think it's what
> > I really meant to say.
> 
> Yes, add a '&& access(c->configfile, F_OK) to that test will make the
> lxc-create -n xxx -f config
> successful, but I don't quite understand the logic here, in what situation
> will this test fail?

I meant file_exists(c->configfile).

It'll "fail" if the container has not yet been created, but only
the rootfs path exists.  Which is exactly what you want.

-serge