# GitHub Actions "pwsh: command not found" on an Ubuntu runner

> Fix the GitHub Actions error where a step with "shell: pwsh" fails on an Ubuntu runner because PowerShell Core is not installed.

Source: https://latchkey.dev/learn/github-actions/github-actions-shell-pwsh-not-found-ubuntu  
Updated: 2026-06-26

A step declared "shell: pwsh" but the chosen runner image does not have PowerShell Core on PATH. GitHub-hosted Ubuntu images bundle pwsh, but custom or self-hosted runners may not.

## Diagnose it: print the context before you change anything

Most workflow-expression bugs are not syntax errors, they are an expression reading something that is empty. GitHub resolves a missing property to an empty string instead of failing the run, so a wrong reference looks like a logic bug rather than a mistake. Dump the contexts first and you will usually see the answer immediately.

```.github/workflows/ci.yml
- name: Dump contexts
  run: |
    echo '--- github ---'   ; echo '${{ toJSON(github) }}'
    echo '--- needs ---'    ; echo '${{ toJSON(needs) }}'
    echo '--- steps ---'    ; echo '${{ toJSON(steps) }}'
    echo '--- matrix ---'   ; echo '${{ toJSON(matrix) }}'
    echo '--- inputs ---'   ; echo '${{ toJSON(inputs) }}'
```

> An empty `{}` or a blank line is the finding. It means the context is not populated at that point, which is a different problem from the value being wrong, and it needs a different fix.

## Check the context is allowed where you used it

Contexts are not available everywhere. The same expression can be valid in a step `if` and invalid in a job `if`, which is why an expression that works in one workflow fails when moved.

| Where you wrote it | Contexts available there |
| --- | --- |
| `run-name` | `github`, `inputs`, `vars` |
| `concurrency` | `github`, `inputs`, `vars` |
| Top-level `env` | `github`, `secrets`, `inputs`, `vars` |
| `jobs.<id>.if` | `github`, `needs`, `vars`, `inputs` |
| `jobs.<id>.steps.if` | `github`, `needs`, `strategy`, `matrix`, `job`, `runner`, `env`, `vars`, `steps`, `inputs` |
| `jobs.<id>.outputs` | Full access, including `secrets` |
| Reusable workflow `outputs` | `github`, `jobs`, `vars`, `inputs` |

> The most common trap in this table: `steps` and `matrix` are available in a **step** `if` but not in a **job** `if`. Moving a condition up a level silently breaks it.

## Catch it before it reaches CI

Every failure in this cluster is statically detectable. `actionlint` parses workflow expressions, checks context availability against the same rules above, and validates `needs` references, so these bugs never need to cost you a run.

```Terminal
# one-off
docker run --rm -v "$(pwd):/repo" --workdir /repo rhysd/actionlint:latest -color

# as a job, before anything expensive runs
- uses: actions/checkout@v4
- run: |
    bash <(curl -s https://raw.githubusercontent.com/rhysd/actionlint/main/scripts/download-actionlint.bash)
    ./actionlint -color
```

## FAQ

### What causes GitHub Actions "pwsh: command not found" on an Ubuntu runner?

There are 2 common causes: self-hosted or custom image without pwsh and step assumes windows shell semantics. PowerShell Core is not part of the base OS.

### How do I fix GitHub Actions "pwsh: command not found" on an Ubuntu runner?

There are 2 fixes depending on which cause you have: use bash on linux runners and install powershell if pwsh is required. Work through them in order, since the first is the most common.

### What does GitHub Actions "pwsh: command not found" on an Ubuntu runner actually mean?

A step with "shell: pwsh" fails to start, reporting that pwsh cannot be found, even though "bash" steps run fine.

### How do I stop GitHub Actions "pwsh: command not found" on an Ubuntu runner happening again?

Match the "shell:" value to what the runner image actually ships. The prevention section lists 2 changes that keep it from recurring.

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Latchkey runs CI/CD that repairs its own failures. Agent entry points: https://latchkey.dev/agent.txt, https://latchkey.dev/openapi.json, https://latchkey.dev/llms.txt