Merge pull request #2823 from TomSweeneyRedHat/dev/tsweeney/override_…

…from

Allow FROM to be overriden with from option

cmd/buildah/bud.go

@@ -318,6 +318,7 @@ func budCmd(c *cobra.Command, inputArgs []string, iopts budOptions) error {
 		DropCapabilities:        iopts.CapDrop,
 		Err:                     stderr,
 		ForceRmIntermediateCtrs: iopts.ForceRm,
+		From:                    iopts.From,
 		IDMappingOptions:        idmappingOptions,
 		IIDFile:                 iopts.Iidfile,
 		Isolation:               isolation,

docs/buildah-bud.md

@@ -61,6 +61,9 @@ instructions read from the Containerfiles in the same way that environment
 variables are, but which will not be added to environment variable list in the
 resulting image's configuration.
 
+Please refer to the [BUILD TIME VARIABLES](#build-time-variables) section for the
+list of variables that can be overridden within the Containerfile at run time.
+
 **--cache-from**
 
 Images to utilise as potential cache sources. Buildah does not currently support caching so this is a NOOP.
@@ -264,6 +267,11 @@ Recognized formats include *oci* (OCI image-spec v1.0, the default) and
 Note: You can also override the default format by setting the BUILDAH\_FORMAT
 environment variable.  `export BUILDAH_FORMAT=docker`
 
+**--from**
+
+Overrides the first `FROM` instruction within the Containerfile.  If there are multiple
+FROM instructions in a Containerfile, only the first is changed.
+
 **-h**, **--help**
 
 Print usage statement
@@ -666,6 +674,23 @@ will convert /foo into a `shared` mount point.  The propagation properties of th
 mount can be changed directly. For instance if `/` is the source mount for
 `/foo`, then use `mount --make-shared /` to convert `/` into a `shared` mount.
 
+## BUILD TIME VARIABLES
+
+The ENV instruction in a Containerfile can be used to define variable values.  When the image
+is built, the values will persist in the container image.  At times it is more convenient to
+change the values in the Containerfile via a command-line option rather than changing the
+values within the Containerfile itself.
+
+The following variables can be used in conjunction with the `--build-arg` option to override the
+corresponding values set in the Containerfile using the `ENV` instruction.
+
+  * HTTP_PROXY
+  * HTTPS_PROXY
+  * FTP_PROXY
+  * NO_PROXY
+
+Please refer to the [Using Build Time Variables](#using-build-time-variables) section of the Examples.
+
 ## EXAMPLE
 
 ### Build an image using local Containerfiles
@@ -727,6 +752,11 @@ buildah bud --dns-search=example.com --dns=223.5.5.5 --dns-option=use-vc .
 
   Note: supported compression formats are 'xz', 'bzip2', 'gzip' and 'identity' (no compression).
 
+### Using Build Time Variables
+#### Replace the value set for the HTTP_PROXY environment variable within the Containerfile.
+
+buildah bud --build-arg=HTTP_PROXY="http://127.0.0.1:8321"
+
 ## ENVIRONMENT
 
 **BUILD\_REGISTRY\_SOURCES**

imagebuildah/build.go

@@ -187,6 +187,9 @@ type BuildOptions struct {
 	LogRusage bool
 	// Excludes is a list of excludes to be used instead of the .dockerignore file.
 	Excludes []string
+	// From is the image name to use to replace the value specified in the first
+	// FROM instruction in the Containerfile
+	From string
 }
 
 // BuildDockerfiles parses a set of one or more Dockerfiles (which may be

imagebuildah/executor.go

@@ -114,6 +114,7 @@ type Executor struct {
 	logRusage                      bool
 	imageInfoLock                  sync.Mutex
 	imageInfoCache                 map[string]imageTypeAndHistoryAndDiffIDs
+	fromOverride                   string
 }
 
 type imageTypeAndHistoryAndDiffIDs struct {
@@ -229,6 +230,7 @@ func NewExecutor(store storage.Store, options BuildOptions, mainNode *parser.Nod
 		jobs:                           jobs,
 		logRusage:                      options.LogRusage,
 		imageInfoCache:                 make(map[string]imageTypeAndHistoryAndDiffIDs),
+		fromOverride:                   options.From,
 	}
 	if exec.err == nil {
 		exec.err = os.Stderr
@@ -245,6 +247,7 @@ func NewExecutor(store storage.Store, options BuildOptions, mainNode *parser.Nod
 			fmt.Fprintf(exec.out, prefix+format+suffix, args...)
 		}
 	}
+
 	for arg := range options.Args {
 		if _, isBuiltIn := builtinAllowedBuildArgs[arg]; !isBuiltIn {
 			exec.unusedArgs[arg] = struct{}{}
@@ -522,6 +525,12 @@ func (b *Executor) Build(ctx context.Context, stages imagebuilder.Stages) (image
 				switch strings.ToUpper(child.Value) { // first token - instruction
 				case "FROM":
 					if child.Next != nil { // second token on this line
+						// If we have a fromOverride, replace the value of
+						// image name for the first FROM in the Containerfile.
+						if b.fromOverride != "" {
+							child.Next.Value = b.fromOverride
+							b.fromOverride = ""
+						}
 						base := child.Next.Value
 						if base != "scratch" {
 							// TODO: this didn't undergo variable and arg

pkg/cli/common.go

@@ -63,6 +63,7 @@ type BudResults struct {
 	IgnoreFile          string
 	File                []string
 	Format              string
+	From                string
 	Iidfile             string
 	Label               []string
 	Logfile             string
@@ -187,6 +188,7 @@ func GetBudFlags(flags *BudResults) pflag.FlagSet {
 	fs.StringVar(&flags.Creds, "creds", "", "use `[username[:password]]` for accessing the registry")
 	fs.BoolVarP(&flags.DisableCompression, "disable-compression", "D", true, "don't compress layers by default")
 	fs.BoolVar(&flags.DisableContentTrust, "disable-content-trust", false, "This is a Docker specific option and is a NOOP")
+	fs.StringVar(&flags.From, "from", "", "image name used to replace the value in the first FROM instruction in the Containerfile")
 	fs.StringVar(&flags.IgnoreFile, "ignorefile", "", "path to an alternate .dockerignore file")
 	fs.StringSliceVarP(&flags.File, "file", "f", []string{}, "`pathname or URL` of a Dockerfile")
 	fs.StringVar(&flags.Format, "format", DefaultFormat(), "`format` of the built image's manifest and metadata. Use BUILDAH_FORMAT environment variable to override.")
@@ -233,6 +235,7 @@ func GetBudFlagsCompletions() commonComp.FlagCompletions {
 	flagCompletion["cert-dir"] = commonComp.AutocompleteDefault
 	flagCompletion["creds"] = commonComp.AutocompleteNone
 	flagCompletion["file"] = commonComp.AutocompleteDefault
+	flagCompletion["from"] = commonComp.AutocompleteDefault
 	flagCompletion["format"] = commonComp.AutocompleteNone
 	flagCompletion["ignorefile"] = commonComp.AutocompleteDefault
 	flagCompletion["iidfile"] = commonComp.AutocompleteDefault

tests/bud.bats

@@ -2430,5 +2430,14 @@ EOF
   expect_output --substring "FROM alpine"
 
   run_buildah 125 bud --network=bogus --signature-policy ${TESTSDIR}/policy.json -t ${target} ${TESTSDIR}/bud/containerfile
-  expect_output "error checking for network namespace: stat bogus: no such file or directory"
+
+}
+
+@test "bud-replace-from-in-containerfile" {
+  _prefetch alpine
+  # override the first FROM (fedora) image in the Containerfile
+  # with alpine, leave the second (busybox) alone.
+  run_buildah bud --signature-policy ${TESTSDIR}/policy.json --from=alpine ${TESTSDIR}/bud/build-with-from
+  expect_output --substring "STEP 1: FROM alpine AS builder"
+  expect_output --substring "STEP 2: FROM busybox"
 }

tests/bud/build-with-from/Containerfile

@@ -0,0 +1,4 @@
+FROM fedora as builder 
+FROM busybox
+COPY --from=builder /bin/df /tmp/df_tester
+