Producing Images From Compiled/Built Code¶
A common first step before building a container image is to build your code in a consistent environment. Stacker provides a hermetically sealed environment in a build-only container to produce the binaries and other artifacts required for the container image. Whether you are building a container image or not, it is a good idea to use stacker's container-based builds to produce your binaries, especially when you need a consistent build environment for all the developers collaborating on the same project.
Go Code Example¶
As an example, let's build a simple go file using stacker:
cat > "hello_stacker.go" << EOF
package main
import "fmt"
func main() {
fmt.Println("Hello Stacker!")
}
EOF
cat > "go_build.stacker.yaml" << EOF
go-build-hello-stacker:
from:
type: docker
url: docker://zothub.io/c3/ubuntu/go-devel-amd64:1.19.2
import:
- ./hello_stacker.go
build_only: true
run: |
# Source Go toolchain env
. /etc/profile
# Setup Go ENV
mkdir -p /go
export GOPATH=/go
mkdir -p /go/src
cd /go/src
# Copy source code to go path
cp /stacker/hello_stacker.go .
# Build code
go build -o hello_stacker hello_stacker.go
# Test code
./hello_stacker
EOF
stacker build -f go_build.stacker.yaml
preparing image hello-go-stacker...
using cached copy of /dev/shm/ravi/hello_stacker.go
loading docker://zothub.io/c3/ubuntu/go-devel-amd64:1.19.2
Copying blob b900f44d647a skipped: already exists
Copying config 3ece5b544e done
Writing manifest to image destination
Storing signatures
cache miss because layer definition was changed
+ . /etc/profile
+ export 'HOME=/go'
+ export 'GOROOT=/opt/go'
+ export 'PATH=/opt/go/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin'
+ mkdir -p /tmp/go/cache
+ export 'GOCACHE=/tmp/go/cache'
+ mkdir -p /go
+ export 'GOPATH=/go'
+ mkdir -p /go/src
+ cd /go/src
+ cp /stacker/hello_stacker.go .
+ go build -o hello_stacker hello_stacker.go
+ ./hello_stacker
Hello Stacker!
The above script creates a go file called hello_stacker.go, then uses a go development container from zothub.io/c3/ubuntu/go-devel-amd:1.19.2 to build hello_stacker.go.
Let's look at details of the stacker file sections used:
| Stacker file Keyword | Description |
|---|---|
from | specifies the base container to be used for this build |
import | import file from host into the build container |
build_only | mark this as a build container to avoid layer creation |
run | build script to execute |
Note cp /stacker/hello_stacker.go . in the run script. Stacker bind mounts all the imported files under a special read-only directory /stacker. This directory can be used in the run script to access the host mounted files in the build script.