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

[Andrei Vagin]

Hi Adrian,

Last time, we discussed that we need a way how to override criu options
which are set by Docker, runc, LXC or other tools.

https://marc.info/?l=openvz-criu&m=152844187925264&w=2

> My idea was to introduce two config files for criu. The first one is exsting one, that
> criu reads from known global place (/etc/...). Then criu parses CLI/RPC options and 
> overrides values read from config. Then should go the 2nd config, which is formatted
> the same way as the 1st one, but it sits not in some other place path to which is
> somehow (I don't know how to pass this knowledge "through" docker/lxd) told to criu
> by the caller. This 2nd config file will override options set via CLI/RPC. Also, since
> the path to this 2nd config file is specified by the caller, if some other criu invocation
> happens in parallel it will not erroneously pick this file's options.
> 

But CRIU_CONFIG_FILE doesn't work this way, does it?

# cat /tmp/criu.cfg 
log-file /tmp/criu.log
# export CRIU_CONFIG_FILE="/tmp/criu.cfg"
# ./criu/criu dump -t 8888888 -v4
# cat /tmp/criu.log | grep Error
(00.001984) Error (criu/util.c:407): Can't open 8888888: No such file or directory
(00.002021) Error (compel/src/lib/infect.c:341): Unable to detach from 8888888: No such process
(00.002056) Error (criu/cr-dump.c:1834): Dumping FAILED.

# unlink /tmp/criu.log 
# ./criu/criu dump -t 8888888 -v4 --log-file dump.log
# cat /tmp/criu.log | grep Error
cat: /tmp/criu.log: No such file or directory

Thanks,
Andrei

On Thu, Jun 28, 2018 at 04:02:32PM +0000, 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.
> 
> 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);
> -- 
> 1.8.3.1
>