Linux/Unix System Administration - Installation and Configuration Storage: ISCSI, DRBD, GlusterFS, and Ceph. File servers: FTP, NFS, and Samba. Web Server: Apache, Tomcat, and Nginx. Database: Mysql, Postgres, MongoDB Cache & Proxy: Squid, Varnish, Nginx, and Lusca. Mail Server: Postfix, Sendmail, IredMail, Qmail, and Zimbra. Automation: Ansibe, Puppet, Chef, and Teraform. Scripting: Bash, Perl, Python, and Ruby. Network Services: DNS, NTP, VPN, and DHCP. Identity Authentication: OpenLDAP, and FreeIPA. Security: IPtables, Firewalld, SELINUX Monitoring: Nagios, Zabbix, collectd, Zenoss, and Netdata. DevOps: Docker, Git, Jenkins, and Selenium.