[CRIU] [PATCH v3 5/7] config: check for CRIU_CONFIG_FILE environment variable

[Adrian Reber]

On Fri, Jul 06, 2018 at 12:33:27PM +0300, Pavel Emelyanov wrote:
> On 06/28/2018 07:02 PM, Adrian Reber wrote:
> > From: Adrian Reber <areber at redhat.com>
> > 
> > To be able to influence, especially via RPC, that another configuration
> > file should be used, this introduces the environment variable
> > CRIU_CONFIG_FILE.
> 
> But how is RPC client supposed to affect CRIU's environment if the latter is
> fork-ed and exec-ed by some (Docker/LXD) daemon?

This seems to dependent on the definition of what a RPC client is.

>From my point of view runc is basically the only RPC client CRIU
currently have besides p.haul.

My idea was, if the RPC client (runc) wants to allow the user to
override RPC settings via configuration file, the RPC client sets
opts.prefer_config_file to True. If the RPC client wants to offer the
possibility to specify a non-default configuration file it can offer
that and tell CRIU by setting the CRIU_CONFIG_FILE environment variable.

I did not expect CRIU_CONFIG_FILE to be set by the user which then calls
docker which then calls runc which then calls CRIU:

user->docker->runc->criu (are there even more layers between the user and criu???)

But if runc sets CRIU_CONFIG_FILE it should work, right?

So from my point of view CRIU_CONFIG_FILE is more for runc to define a
non standard configuration than for the actual user to set one.

		Adrian

> > If set, the file it points to will be used instead of the default
> > configuration files and also instead of the configuration file specified
> > via the command-line.
> > 
> > CRIU now first checks for CRIU_CONFIG_FILE and uses that, if that is not
> > set it looks for '--config FILEPATH' and uses that, if that is not set
> > it uses the default configuration files.
> > 
> > The idea behind this option is that now it is possible for an RPC client
> > to set CRIU_CONFIG_FILE and also set the RPC option
> > opts.prefer_config_file to tell CRIU to prefer the options from a
> > non-default configuration file over the options set via RPC.
> > 
> > Signed-off-by: Adrian Reber <areber at redhat.com>
> > ---
> >  criu/config.c | 9 +++++++++
> >  1 file changed, 9 insertions(+)
> > 
> > diff --git a/criu/config.c b/criu/config.c
> > index f3bf35b..d764832 100644
> > --- a/criu/config.c
> > +++ b/criu/config.c
> > @@ -157,6 +157,7 @@ int init_config(int argc, char **argv, int *global_cfg_argc, int *user_cfg_argc,
> >  {
> >  	bool no_default_config = false;
> >  	char *cfg_file = NULL;
> > +	char *cfg_from_env = getenv("CRIU_CONFIG_FILE");
> >  	int i;
> >  
> >  	/*
> > @@ -188,6 +189,14 @@ int init_config(int argc, char **argv, int *global_cfg_argc, int *user_cfg_argc,
> >  		}
> >  	}
> >  
> > +	/*
> > +	 * If the environment variable CRIU_CONFIG_FILE is set it
> > +	 * will overwrite the configuration file set via '--config'.
> > +	 */
> > +
> > +	if (cfg_from_env)
> > +		cfg_file = cfg_from_env;
> > +
> >  	init_configuration(argc, argv, no_default_config, cfg_file);
> >  	if (global_conf != NULL)
> >  		*global_cfg_argc = count_elements(global_conf);
> > 

		Adrian

-- 
Adrian Reber <adrian at lisas.de>            http://lisas.de/~adrian/
You had mail.  Paul read it, so ask him what it said.