new copy command; scratch image

Author: alexei-led

Dockerfile

@@ -1,35 +1,28 @@
 # syntax = docker/dockerfile:experimental
 
 FROM --platform=${BUILDPLATFORM} golang:1.16-alpine as builder
-
 # passed by buildkit
 ARG TARGETOS
 ARG TARGETARCH
-
 # add CA certificates and TZ for local time
 RUN apk --update add ca-certificates make git
-
 # Create and change to the app directory.
 RUN mkdir -p /go/src/app
 WORKDIR /go/src/app
-
 # Retrieve application dependencies.
 # This allows the container build to reuse cached dependencies.
 # Expecting to copy go.mod and if present go.sum.
 COPY go.mod .
 COPY go.sum .
 RUN --mount=type=cache,target=/go/mod go mod download
-
 # Copy local code to the container image.
 COPY . .
-
 # Build the binary.
 RUN --mount=type=cache,target=/root/.cache/go-build TARGETOS=${TARGETOS} TARGETARCH=${TARGETARCH} make
 
 # final image
-# keep it FROM alpine - need to copy secrets-init to target container
-FROM --platform=${TARGETPLATFORM} alpine:3.13
-
-COPY --from=builder /go/src/app/.bin/secrets-init /usr/local/bin/secrets-init
-
-CMD ["secrets-init", "--version"]
+FROM scratch
+# copy the binary to the production image from the builder stage.
+COPY --from=builder /go/src/app/.bin/secrets-init /secrets-init
+ENTRYPOINT ["/secrets-init"]
+CMD ["--version"]

Makefile

@@ -14,7 +14,7 @@ PLATFORMS     = darwin linux
 ARCHITECTURES = amd64 arm64
 TARGETOS   ?= $(GOOS)
 TARGETARCH ?= $(GOARCH)
-LDFLAGS_VERSION = -X main.Version=$(VERSION) -X main.BuildDate=$(DATE) -X main.GitCommit=$(COMMIT) -X main.GitBranch=$(BRANCH)
+LDFLAGS_VERSION = -s -w -X main.Version=$(VERSION) -X main.BuildDate=$(DATE) -X main.GitCommit=$(COMMIT) -X main.GitBranch=$(BRANCH)
 
 DOCKER  = docker
 GO      = go

main.go

@@ -3,9 +3,11 @@ package main
 import (
 	"context"
 	"fmt"
+	"io"
 	"os"
 	"os/exec"
 	"os/signal"
+	"path/filepath"
 	"runtime"
 	"secrets-init/pkg/secrets"
 	"secrets-init/pkg/secrets/aws"
@@ -41,6 +43,15 @@ func main() {
 				Value: "aws",
 			},
 		},
+		Commands: []*cli.Command{
+			{
+				Name:      "copy",
+				Aliases:   []string{"cp"},
+				Usage:     "copy itself to a destination folder",
+				ArgsUsage: "destination",
+				Action:    copyCmd,
+			},
+		},
 		Name:    "secrets-init",
 		Usage:   "enrich environment variables with secrets from secret manager",
 		Action:  mainCmd,
@@ -61,6 +72,43 @@ func main() {
 	}
 }
 
+func copyCmd(c *cli.Context) error {
+	if c.Args().Len() != 1 {
+		return fmt.Errorf("must specify copy destination")
+	}
+	// full path of current executable
+	src := os.Args[0]
+	// destination path
+	dest := filepath.Join(c.Args().First(), filepath.Base(src))
+	// copy file with current file mode flags
+	sourceFileStat, err := os.Stat(src)
+	if err != nil {
+		return err
+	}
+	if !sourceFileStat.Mode().IsRegular() {
+		return fmt.Errorf("%s is not a regular file", src)
+	}
+	source, err := os.Open(src)
+	if err != nil {
+		return err
+	}
+	srcInfo, err := source.Stat()
+	if err != nil {
+		return err
+	}
+	defer func() { _ = source.Close() }()
+	destination, err := os.Create(dest)
+	if err != nil {
+		return err
+	}
+	defer func() { _ = destination.Close() }()
+	_, err = io.Copy(destination, source)
+	if err != nil {
+		return err
+	}
+	return destination.Chmod(srcInfo.Mode())
+}
+
 func mainCmd(c *cli.Context) error {
 	// Routine to reap zombies (it's the job of init)
 	ctx, cancel := context.WithCancel(context.Background())