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

[Pavel Emelyanov]

On 07/06/2018 01:37 PM, Adrian Reber wrote:
> 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.

:D

>>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?

Right, but my question was exactly about the case you mentioned --  user->docker->runc->criu.
IIRC, this was the unavoidable obstacle lots of people suffer from.

> 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
>