Re: [libvirt] [sandbox PATCH v4 10/21] Image: Add get_command function to Source

On Tue, 2015-09-08 at 17:21 +0100, Daniel P. Berrange wrote: > On Fri, Aug 28, 2015 at 01:47:38PM +0000, Eren Yagdiran wrote: > > Provide a way to know how a template can be started depending on the used source > > DockerSource will need to parse the topmost config file in order to find the igniter command > > --- > > virt-sandbox-image/sources/DockerSource.py | 14 ++++++++++++++ > > virt-sandbox-image/sources/Source.py | 4 ++++ > > 2 files changed, 18 insertions(+) > > > > diff --git a/virt-sandbox-image/sources/DockerSource.py b/virt-sandbox-image/sources/DockerSource.py > > index 760ba6c..3e0362b 100644 > > --- a/virt-sandbox-image/sources/DockerSource.py > > +++ b/virt-sandbox-image/sources/DockerSource.py > > @@ -29,6 +29,15 @@ import os > > import subprocess > > import shutil > > > > +class DockerConfParser(): > > + > > + def __init__(self,jsonfile): > > + with open(jsonfile) as json_file: > > + self.json_data = json.load(json_file) > > + def getRunCommand(self): > > + cmd = self.json_data['container_config']['Cmd'][2] > > + return cmd[cmd.index('"') + 1:cmd.rindex('"')] > > In testing, I found out we should be using 'config' here > not 'container_config', since the latter refers to the > configuration used when the image was built, which is > subtly different from the config that is intended to be > used when in it deployed. > > In particular the 'Cmd' field does not need this string > munging when we use 'config' instead of 'container_config'. > > In researching this, I found out that docker also has an > optional 'Entrypoints' array and if both Entrypoints and > Cmd are specified, we should concatenate them. If the > user provides command line args, then should replace > the 'Cmd' list, but not the 'Entrypoints' list. Finally > some images don'pt define any 'Cmd' or 'Entrypoints' at > all, in which case it seems we should just try using > /bin/sh, in the absence of any user supplied command. Do we really want to have a default to /bin/sh when docker is giving an error to the user?

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