- Linux: RHEL/Debian/Ubuntu, kickstart, PXE, LDAP, SSSD, RPM/Deb package creation, quotas, extended permissions, AppArmor, SeLinux, Centrify, Tripwire, Integrit, OSSEC. 22 years
- Windows: Server (2008 - 2016), Windows client automated deployment (7,8,10,11), Active Directory, Group Policy, WSUS, Certificate Services, AD DNS, AD DHCP, complex multiple forest and domain setups, LDAP. 22 years
- Server software: Apache, Postfix, Qmail, Dovecot, Courier, Nginx, Matamo, Discourse, Wordpress, Mautic,Dolibarr, Revive, Firefly, Cloudron, Coolify, Gitea, Gitlab, GitHub, Git, Jenkins, Rundeck, N8N, Mysql,Postgresql,  LetsEncrypt, ACME, cfssl. 22 years.
- Security: PCI Compliance, security hardening,audits, breach response and mitigation, patch and vulnerability management. 22 years
- Networking: HAProxy, Ubiquiti Unifi, Opnsense, Pfsense, HP, Cisco, Arista, Dell, DNS, DHCP, IPAM, PXE, IPS, IDS, GRE, IPSEC. Wireguard, OpenVPN, Nebula, Tailscale, RADIUS. Mostly layer2 data center/campus/access some WAN,firewall,layer3. 22 years 
- Monitoring: librenms, zabbix, zenoss, nagios 22 years 
- Storage: NFS, Samba, CIFS, Netapp, ZFS, True/Free NAS, 3par, MSA, Equallogic, EMC, generic iscsi. 22 years 
- Virtualization: VmWare, HyperV, KVM, Xen. 22 years.
- Git: branching, merging, multiple teams, external vendors, submodules etc. 15 years
- Containerization: LXC, Docker, Compose.  12 years
- Packer/Ansible 2 years
- Configuration management: Slack, Cfengine, Puppet, FetchApply, Ansible (20 years)
- Currently learning: GCP, AWS, Azure, Kubernetes, Helm (1 year in dev labs)