Linux|22 years|RHEL/Debian/Ubuntu, kickstart, PXE, LDAP, SSSD, RPM/Deb package creation, quotas, extended permissions, clustering, linux virtual server (LVS),NFS Samba  
Windows|22 years|Server (2008  2016), Windows client automated deployment (7,8,10,11), Active Directory (multi forest, multi domain, cross domain trusts, sites and services, schema extension), Exchange,Group Policy, WSUS, Certificate Services, AD DNS, AD DHCP, complex multiple forest and domain setups and Office365 integration and migrarion
Free/Libre/Open Source software|22 years|Apache, Jboss, Tomcat, 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, VScode
Cyber Security|22 years|PCI Compliance (tier 1 implementations), security hardening, audits, breach response/mitigation/remediation, AppArmor, SeLinux, Centrify, OSSEC, Integrit, Tripwire, patch and vulnerability management 
Networking|22 years|Linux Virtual Server, 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 
Monitoring/Alerting|22 years|Uptime kuma, librenms, zabbix, zenoss, nagios 
Virtualization|22 years|VmWare, Parallels,HyperV, KVM, Xen
Containerization|15 years|LXC, Docker,OpenVZ
Configuration management|22 years|Slack, Cfengine, Puppet, FetchApply, Ansible, Hashicorp Packer/Vault
Embedded development|5 years|Raspberry pi, arduino, seeduino, Lego Mindstorms
Programming/Automation|22 years|Bash , J2ME, PHP, Ruby, PowerShell, TCL/TK, Java
Ticket / incident / project management| 22 years| Jira, ServiceNow,Redmine,RT
Git|15 years|branching, merging, multiple teams, external vendors, submodules 
SRE|4 years| Grafana, Promethus, Signoz, Wazuh
LLM|2 years|OpenWebUI, Apple Silicon, QA/validation, RAG, data cleaning/prep