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Many of CRIU's command-line options can also be influenced via configuration files. Configuration files are evaluated in CLI and RPC mode. It is important to know that configuration files are evaluated before the options set via CLI or RPC. This means that whatever is configured in the configuration files will be overwritten by explicitly set values via CLI or RPC.
Configuration File Location
The default configuration files parsed by CRIU, it they are present on the system, are first /etc/criu/default.conf and then $HOME/.criu/default.conf. Settings in the file /etc/criu/default.conf are overridden by settings in $HOME/.criu/default.conf.
Without any additional parameters CRIU configuration file parsing works like this:
/etc/criu/default.conf; these values can be overridden by$HOME/.criu/default.conf; these values can be overridden by- CLI or RPC configuration options
The user can tell CRIU to completely ignore any configuration file in one of the default locations with the --no-default-config option. In this case the user can still tell CRIU to use a configuration file with the --config FILENAME option. CRIU also honours the environment variable CRIU_CONFIG_FILE just as --config FILENAME option.
Configuration File Syntax
Comments are supported using the '#' character. The rest of the line is ignored. Options are the same as command line options without the '--' prefix, use one option per line (with corresponding argument if applicable, divided by whitespaces). If needed, the argument can be provided in double quotes (this should be needed only if the argument contains whitespaces). In case this type of argument contains a literal double quote as well, it can be escaped using the '\' character. Usage of commands is disallowed and all other escape sequences are interpreted literally.
Example of Configuration File
$ cat ~/.criu/default.conf tcp-established work-dir "/home/USERNAME/criu/my \"work\" directory" #this is a comment no-restore-sibling # this is another comment
Configuration Files in RPC Mode
As configuration file settings are overridden by CLI and RPC mode, there is a special RPC options which lets configuration file settings override RPC settings. This is different than the normal sequence and can lead to situation which break the RPC client -> CRIU setup. As this can lead to broken setups the RPC client has to explicitly enable this mode: opts.prefer_config_file = True.