A typical install of logstash-forwarder (lumberjack) is configured to watch a set of files in specific locations and often playing with that file is impossible. However, you might need to load a file into it that it doesn’t typically monitor.
In another situation, you may need to load historic logfiles into LSF. This can be problematic as LSF keeps track of its position in a given file and will often recognise the file as one it has already processed and won’t reimport events it considers as “old”. ...