The CONFIG REWRITE command rewrites the
redis.conf file the server was started with, applying the minimal changes needed to make it reflect the configuration currently used by the server, which may be different compared to the original one because of the use of the CONFIG SET command.
The rewrite is performed in a very conservative way:
savedirectives, but the current configuration has fewer or none as you disabled RDB persistence, all the lines will be blanked.
CONFIG REWRITE is also able to rewrite the configuration file from scratch if the original one no longer exists for some reason. However if the server was started without a configuration file at all, the CONFIG REWRITE will just return an error.
In order to make sure the redis.conf file is always consistent, that is, on errors or crashes you always end with the old file, or the new one, the rewrite is performed with a single
write(2) call that has enough content to be at least as big as the old file. Sometimes additional padding in the form of comments is added in order to make sure the resulting file is big enough, and later the file gets truncated to remove the padding at the end.
Simple string reply:
OK when the configuration was rewritten properly. Otherwise an error is returned.
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