I'm mainly an expert at application administration and learned system administration on the way. Used to work on Windows platforms at the start of my career (> Windows NT4) and in recent years (since 2015) only active on RHEL and CentOS server and Ubuntu desktop. I've worked as admin with several CRM systems (Vantive, PeopleSoft, Salesforce, Clarify) and the underlying databases (mostly Oracle) at first and later also worked with all kinds of applications, Knowledge Base servers, Content Management platforms, Geo Web publishing, Atlassian Confluence and Jira and most recently still maintain a couple of Jenkins Master servers and agents as well as still doing sys admin on Jira. To make my life easier I've learned some Puppet and Git and still want to improve those skills as well as learn Docker, Ansible and Terraform (actually all Hashicorp tools seem interesting).