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-rw-r--r--tools/vm/README.md6
-rw-r--r--tools/vm/defs.bzl11
2 files changed, 12 insertions, 5 deletions
diff --git a/tools/vm/README.md b/tools/vm/README.md
index 898c95fca..1e9859e66 100644
--- a/tools/vm/README.md
+++ b/tools/vm/README.md
@@ -25,6 +25,12 @@ vm_image(
These images can be built manually by executing the target. The output on
`stdout` will be the image id (in the current project).
+For example:
+
+```
+$ bazel build :ubuntu
+```
+
Images are always named per the hash of all the hermetic input scripts. This
allows images to be memoized quickly and easily.
diff --git a/tools/vm/defs.bzl b/tools/vm/defs.bzl
index 0f67cfa92..9af5ad3b4 100644
--- a/tools/vm/defs.bzl
+++ b/tools/vm/defs.bzl
@@ -60,11 +60,12 @@ def _vm_image_impl(ctx):
# Run the builder to generate our output.
echo = ctx.actions.declare_file(ctx.label.name)
resolved_inputs, argv, runfiles_manifests = ctx.resolve_command(
- command = "echo -ne \"#!/bin/bash\\nset -e\\nimage=$(%s)\\necho ${image}\\n\" > %s && chmod 0755 %s" % (
- ctx.files.builder[0].path,
- echo.path,
- echo.path,
- ),
+ command = "\n".join([
+ "set -e",
+ "image=$(%s)" % ctx.files.builder[0].path,
+ "echo -ne \"#!/bin/bash\\necho ${image}\\n\" > %s" % echo.path,
+ "chmod 0755 %s" % echo.path,
+ ]),
tools = [ctx.attr.builder],
)
ctx.actions.run_shell(