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 
Virtualization|22 years|VmWare,Parallels,HyperV,KVM,Xen
Networking|22 years|Linux Virtual Server(LVS),HAProxy,Ubiquiti Unifi,Opnsense,Pfsense,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,Elasticsearch,Logstash,Kibana(ELK)
Storage|22 years|Netapp,EMC,EqualLogic,3par,MSA,TrueNAS/ZFS,iscsi,S3,Azure Storage
Cloud|5 years|AWS,Azure,Kubernetes,Helm,Docker
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|5 years| Grafana,Prometheus,Signoz,Wazuh
LLM|2 years|OpenWebUI,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