Andrew Clay Shafer's contribution to DevOps is both conceptual and organizational: he proposed applying Agile principles to systems administration — a reframing that became foundational — and his accidental meeting with patrick-debois directly produced the first DevOpsDays.
In August 2008, at the Agile Conference in Toronto, Shafer posted a birds-of-a-feather session titled "Agile Infrastructure." Only Debois attended; the session itself was cancelled before it formally began. But the conversation between Shafer and Debois continued, establishing the conceptual frame of infrastructure-as-code and the application of Agile practices to operations. This meeting is the direct precursor to the first devopsdays-conference in October 2009.
Shafer is co-founder of puppet-labs (with Luke Kanies), one of the first modern infrastructure-as-code companies. Puppet the tool — configuration management through declarative code rather than manual administration — operationalized the "Agile Infrastructure" concept Shafer had been advocating. The move from shell scripts and manual server configuration to version-controlled, tested, reproducible infrastructure definitions was a enabling condition for DevOps practice at scale.
The phrase "infrastructure as code" — the framing of infrastructure management as a software engineering discipline, with all that implies (version control, testing, review, automation) — is attributed to or closely associated with Shafer. The concept is now so foundational to DevOps practice that it is easy to forget it required invention: the idea that a server configuration should be treated like source code, not like a handcrafted artifact, was not obvious to the 2008 operations community.
Shafer's intellectual lineage runs through the Agile community (hence the Agile Conference context) and through his own operations practice. He is from the sysadmin world, which gives his advocacy for applying developer disciplines to operations a different character than it would have coming from a developer — he was proposing change from inside the affected practice, not imposing development culture on operations.
His subsequent trajectory after Puppet is less thoroughly documented (20+ years in technology is the record). The Puppet Labs founding, the Agile Infrastructure BOF, and the Debois meeting are his most historically significant contributions to the movement.