I have my bitcoins on a Linux Server. It runs Bitcoin Core 0.14.1.
What do I have to do after Segwit activates?
Bitcoin Core has had the code for segwit since 0.13.1, and your Bitcoin Core 0.14.1 is fully compatible with segwit blocks.
Note that the current release of Bitcoin Core does not create segwit addresses for the Bitcoin main network yet. Therefore, while BIP141 (Segwit) is expected to activate on the network late in August, only a later release of Bitcoin Core will allow you to receive bitcoins that you can spend making use of the witness space.