Old logs are not imported into ES by logstash

Question

When I start logstash, the old logs are not imported into ES.
Only the new request logs are recorded in ES.
Now I've see this in the doc.

Even if I set the start_position=>"beginning", old logs are not inserted.
This only happens when I run logstash on linux.

If I run it with the same config, old logs are imported.
I don't even need to set start_position=>"beginning" on windows.

Any idea about this ?

Answer 1

Please see this line also.

This option only modifies "first contact" situations where a file is new and not seen before. If a file has already been seen before, this option has no effect.

Answer 2

When you read an input log to Logstash, Logstash will keep an record about the position it read on this file, that's call sincedb.

Where to write the sincedb database (keeps track of the current position of monitored log files). 
The default will write sincedb files to some path matching "$HOME/.sincedb*"

So, if you want to import old log files, you must delete all the .sincedb* at your $HOME. Then, you need to set

start_position=>"beginning"

at your configuration file.

Hope this can help you.