From 10beb3920debb0be135ae6cecee2ca55fbc43169 Mon Sep 17 00:00:00 2001
From: Jonathan Boulle <jonathanboulle@gmail.com>
Date: Thu, 12 Feb 2015 12:35:43 -0800
Subject: [PATCH] build: allow setting of stage1 image path

This introduces the ability to set the default stage1 image path for
`rkt run` by setting the environment variable RKT_STAGE1_IMAGE at build
time (i.e when invoking ./build).

The variable should be set to the fully qualified path at which rkt can
find the stage1 image - for example:

	RKT_STAGE1_IMAGE=/usr/lib/rkt/stage1.aci ./build

Rocket will use this environment variable to set the default value for
the stage1-image flag. If the value is _not_ set, it will continue to
use the heuristic it does today to guess the location of the stage1
image, by looking for a file called stage1.aci that is in the same
directory as rkt itself.
---
 build      |  4 +++-
 rkt/run.go | 15 +++++++++------
 2 files changed, 12 insertions(+), 7 deletions(-)

diff --git a/build b/build
index 472f6e6..3bd178a 100755
--- a/build
+++ b/build
@@ -14,7 +14,9 @@ export GOPATH=${PWD}/gopath
 eval $(go env)
 
 echo "Building rkt (stage0)..."
-go build -o $GOBIN/rkt ${REPO_PATH}/rkt
+go build -o ${GOBIN}/rkt \
+	${RKT_STAGE1_IMAGE:+-ldflags "-X main.defaultStage1Image '${RKT_STAGE1_IMAGE}'"} \
+	${REPO_PATH}/rkt
 
 if [[ "$OSTYPE" == "linux-gnu" ]]; then
 	echo "Building network plugins..."
diff --git a/rkt/run.go b/rkt/run.go
index 8fbf9fc..fb9bb0d 100644
--- a/rkt/run.go
+++ b/rkt/run.go
@@ -31,6 +31,8 @@ import (
 )
 
 var (
+	defaultStage1Image string // either set by linker, or guessed in init()
+
 	flagStage1Image      string
 	flagVolumes          volumeList
 	flagPrivateNet       bool
@@ -48,14 +50,15 @@ They will be checked in that order and the first match will be used.`,
 func init() {
 	commands = append(commands, cmdRun)
 
-	// try discover the directory rkt is running from, assume the default stage1.aci is stored alongside it.
-	defaultStage1Image := ""
-	exePath, err := os.Readlink("/proc/self/exe")
-	if err == nil {
-		defaultStage1Image = filepath.Join(filepath.Dir(exePath), "stage1.aci")
+	// if not set by linker, try discover the directory rkt is running
+	// from, and assume the default stage1.aci is stored alongside it.
+	if defaultStage1Image == "" {
+		if exePath, err := os.Readlink("/proc/self/exe"); err == nil {
+			defaultStage1Image = filepath.Join(filepath.Dir(exePath), "stage1.aci")
+		}
 	}
 
-	cmdRun.Flags.StringVar(&flagStage1Image, "stage1-image", defaultStage1Image, `image to use as stage1. Local paths and http/https URLs are supported. By default, Rocket will look for a file called "stage1.aci" in the same directory as rkt itself`)
+	cmdRun.Flags.StringVar(&flagStage1Image, "stage1-image", defaultStage1Image, `image to use as stage1. Local paths and http/https URLs are supported. If empty, Rocket will look for a file called "stage1.aci" in the same directory as rkt itself`)
 	cmdRun.Flags.Var(&flagVolumes, "volume", "volumes to mount into the shared container environment")
 	cmdRun.Flags.BoolVar(&flagPrivateNet, "private-net", false, "give container a private network")
 	cmdRun.Flags.BoolVar(&flagSpawnMetadataSvc, "spawn-metadata-svc", false, "launch metadata svc if not running")