Setting a value of debug results in every event and action packet being written to the log file.

将值设置为debug会导致将每个事件和动作包写到日志文件。

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If a packet matches a rule, the kernel performs the action specified by the target of that rule on the packet.

如果信息包与某条规则匹配，那么内核就对该信息包执行由该规则的目标指定的操作。

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Each chain can have a policy that defines "a default target", i.e. a default action to perform, if a packet doesn't match any rule in that chain.

每个链都可以有一个策略，它定义“缺省目标”，也就是要执行的缺省操作，当信息包与链中的任何规则都不匹配时，执行此操作。

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