Linux|22 years|RHEL,Debian,Ubuntu,kickstart,PXE,  LDAP,SSSD,RPM/Deb package creation,  quotas,extended permissions, clustering,NFS,Samba
Unix|5 years|HPUX/Solaris
Windows|22 years|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 
Free/Libre/Open Source software|22 years|Apache,Postfix,Qmail,Dovecot,Courier IMAP,Nginx,Matamo,Discourse,Wordpress,  Mautic,Dolibarr,Revive Ad Server,Firefly,Cloudron,Coolify,Gitea,  HomeAssistant,  Jenkins,Rundeck,N8N,  LetsEncrypt,ACME,cfssl
Databases|22 years| MySQL,PostgreSQL,  Dbeaver,PHPMyAdmin,PostGIS
Cyber Security|22 years|PCI Compliance (tier 1 implementations),OpenVAS<, Lynis, security hardening, audits, breach response and mitigation, patch and vulnerability management. AppArmor, SeLinux, Centrify, Tripwire, Integrit, OSSEC 
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|22 years|Uptime Kuma, Librenms, Zabbix, Zenoss, Nagios, ELK (Elasticsearch, Logstash, Kibana)
Virtualization|22 years|VmWare, Parallels,HyperV, KVM, Xen
Cloud|5 years|AWS, Azure, GCP, Kubernetes
Containerization|15 years|LXC, Docker,OpenVZ
Configuration management/InfrastructureAsCode(IAC)|22 years|FetchApply, Terraform/OpenTOfU,Ansible, AWX,Hashicorp Packer/Vault
Ticket / incident / project management| 22 years| Jira, ServiceNow,Redmine,RT
Git|15 years|Branching, merging, multiple teams, external vendors, submodules 
SRE|4 years| Grafana, Prometheus, Signoz, Wazuh
LLM|2 years|OpenWebUI, Apple Silicon, QA/validation, RAG, data cleaning/prep
Programming|5 years|J2ME,PHP,Ruby,TCL/TK,Java,C,C++
Automation|22 years|Bash,YAML,TOML,PowerShell,Perl
Embedded development|5 years|Raspberry pi, arduino, seeduino, Lego Mindstorms