Add --no-hostname option to buildah containers

Fixes: https://github.com/containers/buildah/issues/5093

Signed-off-by: Daniel J Walsh <dwalsh@redhat.com>

cmd/buildah/run.go

@@ -27,6 +27,7 @@ type runInputOptions struct {
 	mounts      []string
 	runtime     string
 	runtimeFlag []string
+	noHostname  bool
 	noHosts     bool
 	noPivot     bool
 	terminal    bool
@@ -70,6 +71,7 @@ func init() {
 	// Do not set a default runtime here, we'll do that later in the processing.
 	flags.StringVar(&opts.runtime, "runtime", util.Runtime(), "`path` to an alternate OCI runtime")
 	flags.StringSliceVar(&opts.runtimeFlag, "runtime-flag", []string{}, "add global flags for the container runtime")
+	flags.BoolVar(&opts.noHostname, "no-hostname", false, "do not override the /etc/hostname file within the container")
 	flags.BoolVar(&opts.noHosts, "no-hosts", false, "do not override the /etc/hosts file within the container")
 	flags.BoolVar(&opts.noPivot, "no-pivot", false, "do not use pivot root to jail process inside rootfs")
 	flags.BoolVarP(&opts.terminal, "terminal", "t", false, "allocate a pseudo-TTY in the container")
@@ -141,6 +143,7 @@ func runCmd(c *cobra.Command, args []string, iopts runInputOptions) error {
 		Hostname:         iopts.hostname,
 		Runtime:          iopts.runtime,
 		Args:             runtimeFlags,
+		NoHostname:       iopts.noHostname,
 		NoHosts:          iopts.noHosts,
 		NoPivot:          noPivot,
 		User:             c.Flag("user").Value.String(),

define/build.go

@@ -64,6 +64,9 @@ type CommonBuildOptions struct {
 	LabelOpts []string
 	// MemorySwap limits the amount of memory and swap together.
 	MemorySwap int64
+	// NoHostname tells the builder not to create /etc/hostname content when running
+	// containers.
+	NoHostname bool
 	// NoHosts tells the builder not to create /etc/hosts content when running
 	// containers.
 	NoHosts bool

docs/buildah-build.1.md

@@ -645,9 +645,15 @@ Valid _mode_ values are:
 
 Do not use existing cached images for the container build. Build from the start with a new set of cached layers.
 
+**--no-hostname**
+
+Do not create the _/etc/hostname_ file in the container for RUN instructions.
+
+By default, Buildah manages the _/etc/hostname_ file, adding the container's own hostname.  When the **--no-hostname** option is set, the image's _/etc/hostname_ will be preserved unmodified if it exists.
+
 **--no-hosts**
 
-Do not create _/etc/hosts_ for the container.
+Do not create the _/etc/hosts_ file in the container for RUN instructions.
 
 By default, Buildah manages _/etc/hosts_, adding the container's own IP address.
 **--no-hosts** disables this, and the image's _/etc/hosts_ will be preserved unmodified. Conflicts with the --add-host option.

docs/buildah-run.1.md

@@ -217,9 +217,15 @@ Valid _mode_ values are:
         host, using the loopback interface instead of the tap interface for improved
         performance
 
+**--no-hostname**
+
+Do not create the _/etc/hostname_ file in the container for RUN instructions.
+
+By default, Buildah manages the _/etc/hostname_ file, adding the container's own hostname.  When the **--no-hostname** option is set, the image's _/etc/hostname_ will be preserved unmodified if it exists.
+
 **--no-hosts**
 
-Do not create _/etc/hosts_ for the container.
+Do not create the _/etc/hosts_ file in the container for RUN instructions.
 
 By default, Buildah manages _/etc/hosts_, adding the container's own IP address.
 **--no-hosts** disables this, and the image's _/etc/hosts_ will be preserved unmodified.

imagebuildah/executor.go

@@ -103,6 +103,7 @@ type Executor struct {
 	layerLabels             []string
 	annotations             []string
 	layers                  bool
+	noHostname              bool
 	noHosts                 bool
 	useCache                bool
 	removeIntermediateCtrs  bool
@@ -270,6 +271,7 @@ func newExecutor(logger *logrus.Logger, logPrefix string, store storage.Store, o
 		layerLabels:                    append([]string{}, options.LayerLabels...),
 		annotations:                    append([]string{}, options.Annotations...),
 		layers:                         options.Layers,
+		noHostname:                     options.CommonBuildOpts.NoHostname,
 		noHosts:                        options.CommonBuildOpts.NoHosts,
 		useCache:                       !options.NoCache,
 		removeIntermediateCtrs:         options.RemoveIntermediateCtrs,

imagebuildah/stage_executor.go

@@ -622,6 +622,7 @@ func (s *StageExecutor) Run(run imagebuilder.Run, config docker.Config) error {
 		Logger:           s.executor.logger,
 		Mounts:           append([]Mount{}, s.executor.transientMounts...),
 		NamespaceOptions: namespaceOptions,
+		NoHostname:       s.executor.noHostname,
 		NoHosts:          s.executor.noHosts,
 		NoPivot:          os.Getenv("BUILDAH_NOPIVOT") != "",
 		Quiet:            s.executor.quiet,

pkg/cli/common.go

@@ -76,6 +76,7 @@ type BudResults struct {
 	Logfile             string
 	LogSplitByPlatform  bool
 	Manifest            string
+	NoHostname          bool
 	NoHosts             bool
 	NoCache             bool
 	Timestamp           int64
@@ -246,8 +247,9 @@ func GetBudFlags(flags *BudResults) pflag.FlagSet {
 		panic(fmt.Sprintf("error marking the rusage-logfile flag as hidden: %v", err))
 	}
 	fs.StringVar(&flags.Manifest, "manifest", "", "add the image to the specified manifest list. Creates manifest list if it does not exist")
-	fs.BoolVar(&flags.NoHosts, "no-hosts", false, "do not create new /etc/hosts files for RUN instructions, use the one from the base image.")
 	fs.BoolVar(&flags.NoCache, "no-cache", false, "do not use existing cached images for the container build. Build from the start with a new set of cached layers.")
+	fs.BoolVar(&flags.NoHostname, "no-hostname", false, "do not create new /etc/hostname file for RUN instructions, use the one from the base image.")
+	fs.BoolVar(&flags.NoHosts, "no-hosts", false, "do not create new /etc/hosts file for RUN instructions, use the one from the base image.")
 	fs.String("os", runtime.GOOS, "set the OS to the provided value instead of the current operating system of the host")
 	fs.StringArrayVar(&flags.OSFeatures, "os-feature", []string{}, "set required OS `feature` for the target image in addition to values from the base image")
 	fs.StringVar(&flags.OSVersion, "os-version", "", "set required OS `version` for the target image instead of the value from the base image")

pkg/parse/parse.go

@@ -104,6 +104,7 @@ func CommonBuildOptionsFromFlagSet(flags *pflag.FlagSet, findFlagFunc func(name
 		}
 	}
 
+	noHostname, _ := flags.GetBool("no-hostname")
 	noHosts, _ := flags.GetBool("no-hosts")
 
 	addHost, _ := flags.GetStringSlice("add-host")
@@ -183,6 +184,7 @@ func CommonBuildOptionsFromFlagSet(flags *pflag.FlagSet, findFlagFunc func(name
 		IdentityLabel: types.NewOptionalBool(identityLabel),
 		Memory:        memoryLimit,
 		MemorySwap:    memorySwap,
+		NoHostname:    noHostname,
 		NoHosts:       noHosts,
 		OmitHistory:   omitHistory,
 		ShmSize:       findFlagFunc("shm-size").Value.String(),

run.go

@@ -86,7 +86,9 @@ type RunOptions struct {
 	Runtime string
 	// Args adds global arguments for the runtime.
 	Args []string
-	// NoHosts use the images /etc/hosts file
+	// NoHostname won't create new /etc/hostname file
+	NoHostname bool
+	// NoHosts won't create new /etc/hosts file
 	NoHosts bool
 	// NoPivot adds the --no-pivot runtime flag.
 	NoPivot bool

run_linux.go

@@ -269,16 +269,13 @@ func (b *Builder) Run(command []string, options RunOptions) error {
 		bindFiles[config.DefaultHostsFile] = hostFile
 	}
 
-	// generate /etc/hostname if the user intentionally did not override
-	if !(contains(volumes, "/etc/hostname")) {
-		if _, ok := bindFiles["/etc/hostname"]; !ok {
-			hostFile, err := b.generateHostname(path, spec.Hostname, rootIDPair)
-			if err != nil {
-				return err
-			}
-			// Bind /etc/hostname
-			bindFiles["/etc/hostname"] = hostFile
+	if !options.NoHostname && !(contains(volumes, "/etc/hostname")) {
+		hostFile, err := b.generateHostname(path, spec.Hostname, rootIDPair)
+		if err != nil {
+			return err
 		}
+		// Bind /etc/hostname
+		bindFiles["/etc/hostname"] = hostFile
 	}
 
 	if !contains(volumes, resolvconf.DefaultResolvConf) && options.ConfigureNetwork != define.NetworkDisabled && !(len(b.CommonBuildOpts.DNSServers) == 1 && strings.ToLower(b.CommonBuildOpts.DNSServers[0]) == "none") {

tests/bud.bats

@@ -5258,6 +5258,27 @@ _EOF
     assert "$output" =~ ".*accepts at most 1 arg\(s\), received 2" "Should fail when passed extra arg after context directory"
 }
 
+@test "bud with --no-hostname" {
+  skip_if_no_runtime
+
+  _prefetch alpine
+
+  run_buildah build --no-cache -t testbud \
+                  $WITH_POLICY_JSON $BUDFILES/no-hostname
+  assert "${lines[2]}" != "localhost" "Should be set to something other then localhost"
+
+  run_buildah build --no-hostname --no-cache -t testbud \
+                  $WITH_POLICY_JSON \
+		  $BUDFILES/no-hostname
+  assert "${lines[2]}" == "localhost" "Should be set to localhost"
+
+  run_buildah 1 build --network=none --no-hostname --no-cache -t testbud \
+                  $WITH_POLICY_JSON \
+		  -f $BUDFILES/no-hostname/Containerfile.noetc \
+		  $BUDFILES/no-hostname
+  assert "$output" =~ ".*ls: /etc: No such file or directory" "/etc/ directory should be gone"
+}
+
 @test "bud with --add-host" {
   skip_if_no_runtime
 

tests/bud/no-hostname/Containerfile

@@ -0,0 +1,3 @@
+from alpine
+run cat /etc/hostname
+

tests/bud/no-hostname/Containerfile.noetc

@@ -0,0 +1,3 @@
+from alpine
+RUN mv /etc /usr/
+RUN ls -l /etc

tests/run.bats

@@ -295,6 +295,14 @@ function configure_and_check_user() {
 	hostname=$output
 	run_buildah run --hostname foobar $cid cat /etc/hostname
 	expect_output $hostname
+	run_buildah from --quiet --pull=false $WITH_POLICY_JSON alpine
+	cid=$output
+	run_buildah inspect --format "{{ .ContainerID }}" $cid
+	id=$output
+	run_buildah run $cid cat /etc/hostname
+	expect_output "${id:0:12}"
+	run_buildah run --no-hostname $cid cat /etc/hostname
+	expect_output 'localhost'
 }
 
 @test "run --volume" {