He sacked his acting Director of National Intelligence when one of his underlings went and told the House Intel Committee that Russia was meddling again to get Trump reelected last Thursday. He was especially pissed that Adam Schiff heard the report. It was actually pretty moot, because the acting DNI had to go by March 12. But Trump took him out early to install a yes man as acting DNI.
Trump mostly uses acting positions so they don't have to be confirmed by the Senate. Which is pretty silly because the majority would line up to kiss his ass if he asked.