Runner environment - paths and environment variables

Linux runners follow the GitHub-hosted runner layout wherever a workflow can depend on it. Windows runners keep the self-hosted layout. This page lists the paths a job sees and the environment variables RunsOn adds to every job, on Linux and Windows, for both Flex and Fleet.

Paths#

	Linux	Windows
Runner work folder	`/home/runner/work`	`C:\actions-runner\_work`
`GITHUB_WORKSPACE`	`/home/runner/work/<repo>/<repo>`	`C:\actions-runner\_work\<repo>\<repo>`
`RUNNER_TEMP`	`/home/runner/work/_temp`	`C:\actions-runner\_work\_temp`
Job user and home	`runner`, `/home/runner`	`Administrator`
`RUNNER_TOOL_CACHE`	`/opt/hostedtoolcache`	Set by the image
RunsOn files (`RUNS_ON_HOME`)	`/runs-on`	`C:\runs-on`
Sticky disk mount	`/mnt/runs-on/stickydisk`	`C:\runs-on\stickydisk`
EFS mount (`extras=efs`, Flex only)	`/mnt/efs`	Not available
tmpfs volume (`extras=tmpfs`)	`/mnt/tmpfs`	Not available

On instance types with local NVMe, the same paths stay in place; RunsOn moves their storage, not their location.

Linux workspace#

Linux jobs run under /home/runner/work, the same directory as on GitHub-hosted Linux runners. Tools that record absolute paths, such as test reporters that write sharded blob reports or coverage files, therefore produce artifacts that a job on a GitHub-hosted runner can consume, and the other way round. You can move one job of a producer and consumer pair to RunsOn without moving the other.

/home/runner/_work remains available as a link to /home/runner/work, so preinstall hooks, scripts, and workflows that hardcode it keep working. Tools still report the /home/runner/work path in their output.

Windows workspace#

Windows jobs run under C:\actions-runner\_work. GitHub-hosted Windows runners use D:\a, so absolute paths recorded on one do not resolve on the other.

Environment variables#

RunsOn sets these variables in every job, in addition to the variables GitHub sets ↗. It writes them to GITHUB_ENV when the job starts, so a step’s env overrides them, but workflow- and job-level env do not.

Variable	Example	Description
`RUNS_ON_VERSION`	`v3.5.0`	RunsOn release that launched the runner.
`RUNS_ON_STACK_NAME`	`runs-on`	RunsOn stack that launched the runner.
`RUNS_ON_RUNNER_NAME`	`runs-on--i-0123456789abcdef0--…`	Runner name registered with GitHub.
`RUNS_ON_INSTANCE_ID`	`i-0123456789abcdef0`	EC2 instance ID.
`RUNS_ON_INSTANCE_TYPE`	`c8i.large`	EC2 instance type.
`RUNS_ON_INSTANCE_LIFECYCLE`	`spot`	`spot` or `on-demand`.
`RUNS_ON_INSTANCE_LAUNCHED_AT`	`2026-10-08T10:31:41Z`	Time RunsOn scheduled the runner for the job, in RFC 3339.
`RUNS_ON_AMI_ID`	`ami-0123456789abcdef0`	AMI the instance booted from.
`RUNS_ON_AGENT_ARCH`	`x64`	Runner architecture.
`RUNS_ON_AWS_REGION`	`us-east-1`	AWS region of the runner.
`RUNS_ON_AWS_AZ`	`us-east-1a`	Availability zone of the runner.
`RUNS_ON_S3_BUCKET_CACHE`	`runs-on-s3bucketcache-…`	Stack cache bucket. See Docker caching.
`RUNS_ON_S3_CACHE_REPO_PREFIX`	`cache/repo/<owner>/<repo>`	Per-repository prefix in the cache bucket.
`RUNS_ON_HOME`	`/runs-on`	Directory holding RunsOn files on the runner.
`RUNS_ON_AGENT_USER`	`runner`	Linux job user. Windows jobs run as `Administrator`.

Set by features#

Variable	Set when	Description
`ACTIONS_CACHE_URL`, `ACTIONS_RESULTS_URL`, `ACTIONS_CACHE_SERVICE_V2`	`extras=s3-cache`	Point `actions/cache` and compatible tools at the runner’s S3-backed cache.
`RUNS_ON_ECR_CACHE`	Ephemeral registry enabled on the stack	Ephemeral ECR registry URI. With `extras=ecr-cache` on Linux, Docker is already logged in to it. Without the extra, or on Windows, only step shells on the host see it, not the `env` context or job containers.
`RUNS_ON_ECR_PULL_THROUGH_CACHE`	Pull-through cache rules configured on the stack	ECR registry host of the pull-through cache. With `extras=ecr-pull-through` on Linux, Docker is already logged in to it. Without the extra, or on Windows, only step shells on the host see it, not the `env` context or job containers.
`RUNS_ON_EFS_ID`	EFS enabled on the stack (Flex only)	EFS file system ID.
`RUNS_ON_STICKYDISK_DIR`, `RUNS_ON_STICKYDISK_NAME`, `RUNS_ON_STICKYDISK_READY_FILE`, `RUNS_ON_STICKYDISK_UNAVAILABLE_FILE`	Sticky disk requested	Sticky disk mount and readiness files.
`RUNS_ON_POOL_NAME`, `RUNS_ON_POOL_STANDBY_TYPE`	Job served by a warm pool	Pool name, and `hot` or `stopped`.
`TRACEPARENT`	Job traces exported with OpenTelemetry	Trace context of the job, so spans your workflow sends join the job’s trace.
`OTEL_EXPORTER_OTLP_ENDPOINT`, `OTEL_EXPORTER_OTLP_PROTOCOL`	Local OpenTelemetry collector running	Loopback OTLP/HTTP receiver. RunsOn keeps them out of `GITHUB_ENV`, so `env` at any level overrides them. Job containers do not receive them.
`GITHUB_SERVER_URL`, `GITHUB_API_URL`, `GITHUB_HOST`	GitHub.com or GHE.com	Set for tools such as the Copilot coding agent that expect them on self-hosted runners. GitHub Enterprise Server keeps the runner’s own values.

Other RUNS_ON_* variables you may see in a job are internal to RunsOn and can change between releases.