release: prep v0.1.10 changelog

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

CHANGELOG.md

@@ -10,6 +10,16 @@ changed between versions.
 
 ## [Unreleased]
 
+## [v0.1.10] - 2026-05-03
+
+### Added
+
+- README now includes an animated demo GIF showing the typical
+  sandbox lifecycle (`vm run`, host-side `ssh demo.vm`, stop/start
+  with file persistence, `vm exec`, `curl http://demo.vm`). The
+  recording script lives at `assets/demo.tape` and is rendered with
+  [VHS](https://github.com/charmbracelet/vhs).
+
 ## [v0.1.9] - 2026-05-01
 
 ### Fixed
@@ -302,7 +312,8 @@ root filesystem and network, and exits on demand.
   the swap rather than starting up against an incompatible store.
 - Linux only. amd64 only. KVM required.
 
-[Unreleased]: https://git.thaloco.com/thaloco/banger/compare/v0.1.9...HEAD
+[Unreleased]: https://git.thaloco.com/thaloco/banger/compare/v0.1.10...HEAD
+[v0.1.10]: https://git.thaloco.com/thaloco/banger/releases/tag/v0.1.10
 [v0.1.9]: https://git.thaloco.com/thaloco/banger/releases/tag/v0.1.9
 [v0.1.8]: https://git.thaloco.com/thaloco/banger/releases/tag/v0.1.8
 [v0.1.7]: https://git.thaloco.com/thaloco/banger/releases/tag/v0.1.7

README.md

@@ -2,6 +2,8 @@
 
 One-command development sandboxes on Firecracker microVMs.
 
+![banger demo](assets/banger.gif)
+
 Spin up a clean Linux VM with your repo and tooling preloaded, drop
 into ssh, and tear it down — all from one command. banger is built
 for the dev loop, not the server use case: guests are short-lived,

assets/demo.tape

@@ -0,0 +1,112 @@
+# banger hero demo — VHS tape
+# Render with: vhs assets/demo.tape
+
+Output assets/banger.gif
+
+Require banger
+Require ssh
+Require curl
+
+Set Shell "bash"
+Set FontSize 14
+Set LineHeight 1.4
+Set Width 1200
+Set Height 720
+Set Padding 20
+Set Theme "Catppuccin Frappe"
+Set TypingSpeed 66ms
+
+# Off-camera reset: enable bash syntax highlighting via ble.sh, prompt
+# styling, drop any prior demo VM, and clear the screen.
+Hide
+Type "source ~/.local/share/blesh/ble.sh --noattach"
+Enter
+Sleep 200ms
+Type "bleopt complete_auto_complete= complete_auto_history="
+Enter
+Sleep 100ms
+Type `export PS1="\n$PS1"`
+Enter
+Sleep 200ms
+Type "[[ ${BLE_VERSION-} ]] && ble-attach"
+Enter
+Sleep 400ms
+Type "ble-face -s syntax_error fg=red"
+Enter
+Sleep 100ms
+Type "banger vm kill demo 2>/dev/null; banger vm delete demo 2>/dev/null; clear"
+Enter
+Sleep 500ms
+Show
+
+Type "banger vm run --nat --name demo"
+Enter
+Wait+Line /demo:~#/
+Sleep 1.4s
+
+Type "uname -a"
+Enter
+Sleep 1.4s
+
+Type "exit"
+Enter
+Wait
+Sleep 700ms
+
+Type "banger vm list"
+Enter
+Wait
+Sleep 1.8s
+
+Type "ssh demo.vm"
+Enter
+Wait+Line /demo:~#/
+Sleep 500ms
+
+Type "touch foo bar baz"
+Enter
+Sleep 700ms
+
+Type "ls"
+Enter
+Sleep 1.4s
+
+Type "exit"
+Enter
+Sleep 700ms
+
+Type "banger vm stop demo"
+Enter
+Wait
+Sleep 1s
+
+Type "banger vm start demo"
+Enter
+Wait
+Sleep 1s
+
+Type "banger vm exec demo -- ls"
+Enter
+Wait
+Sleep 1.4s
+
+Type "banger vm exec demo -- docker run -d -p 80:80 nginx"
+Enter
+Wait
+Sleep 1.6s
+
+Type "banger vm ports demo"
+Enter
+Wait
+Sleep 2s
+
+Type "curl http://demo.vm"
+Sleep 1.2s
+Enter
+Wait
+Sleep 4s
+
+Type "banger vm kill demo && banger vm delete demo"
+Enter
+Wait
+Sleep 3s

internal/daemon/capabilities.go

@@ -247,6 +247,9 @@ func (c workDiskCapability) PrepareHost(ctx context.Context, vm *model.VMRecord,
 	if err := c.ws.ensureAuthorizedKeyOnWorkDisk(ctx, vm, image, prep); err != nil {
 		return err
 	}
+	if err := c.ws.ensureHushLoginOnWorkDisk(ctx, vm); err != nil {
+		return err
+	}
 	if err := c.ws.ensureGitIdentityOnWorkDisk(ctx, vm); err != nil {
 		return err
 	}

internal/daemon/tap_pool.go

@@ -6,6 +6,7 @@ import (
 	"strconv"
 	"strings"
 	"sync"
+	"sync/atomic"
 )
 
 const tapPoolPrefix = "tap-pool-"
@@ -16,8 +17,16 @@ type tapPool struct {
 	mu      sync.Mutex
 	entries []string
 	next    int
+	warming bool
 }
 
+// maxConcurrentTapWarmup caps the number of `priv.create_tap` RPCs the
+// warmup loop runs in parallel. Each tap creation is ~4 root-helper
+// shell-outs serialized within one RPC handler; running too many at
+// once just contends on netlink. 8 is the production sweet spot for
+// SMOKE_JOBS=8.
+const maxConcurrentTapWarmup = 8
+
 // initializeTapPool seeds the monotonic pool index from the set of
 // tap names already in use by running/stopped VMs, so newly warmed
 // pool entries don't collide with existing ones. Callers (Daemon.Open)
@@ -41,6 +50,23 @@ func (n *HostNetwork) ensureTapPool(ctx context.Context) {
 	if n.config.TapPoolSize <= 0 {
 		return
 	}
+
+	// Dedupe concurrent warmup invocations. Releases trigger a fresh
+	// ensureTapPool in a goroutine; without this, N parallel releases
+	// would each spin up their own warmup loop racing on n.tapPool.next.
+	n.tapPool.mu.Lock()
+	if n.tapPool.warming {
+		n.tapPool.mu.Unlock()
+		return
+	}
+	n.tapPool.warming = true
+	n.tapPool.mu.Unlock()
+	defer func() {
+		n.tapPool.mu.Lock()
+		n.tapPool.warming = false
+		n.tapPool.mu.Unlock()
+	}()
+
 	for {
 		select {
 		case <-ctx.Done():
@@ -51,28 +77,54 @@ func (n *HostNetwork) ensureTapPool(ctx context.Context) {
 		}
 
 		n.tapPool.mu.Lock()
-		if len(n.tapPool.entries) >= n.config.TapPoolSize {
+		deficit := n.config.TapPoolSize - len(n.tapPool.entries)
+		if deficit <= 0 {
 			n.tapPool.mu.Unlock()
 			return
 		}
-		tapName := fmt.Sprintf("%s%d", tapPoolPrefix, n.tapPool.next)
+		batch := deficit
+		if batch > maxConcurrentTapWarmup {
+			batch = maxConcurrentTapWarmup
+		}
+		// Reserve names up front so concurrent goroutines can't collide
+		// on n.tapPool.next.
+		names := make([]string, batch)
+		for i := range names {
+			names[i] = fmt.Sprintf("%s%d", tapPoolPrefix, n.tapPool.next)
 			n.tapPool.next++
+		}
 		n.tapPool.mu.Unlock()
 
+		var (
+			wg        sync.WaitGroup
+			progress  atomic.Int32
+		)
+		for _, tapName := range names {
+			wg.Add(1)
+			go func(tapName string) {
+				defer wg.Done()
 				if err := n.createTap(ctx, tapName); err != nil {
 					if n.logger != nil {
 						n.logger.Warn("tap pool warmup failed", "tap_device", tapName, "error", err.Error())
 					}
 					return
 				}
-
 				n.tapPool.mu.Lock()
 				n.tapPool.entries = append(n.tapPool.entries, tapName)
 				n.tapPool.mu.Unlock()
-
+				progress.Add(1)
 				if n.logger != nil {
 					n.logger.Debug("tap added to idle pool", "tap_device", tapName)
 				}
+			}(tapName)
+		}
+		wg.Wait()
+
+		// Whole batch failed → bail rather than burn names indefinitely
+		// (the original sequential loop bailed on first error too).
+		if progress.Load() == 0 {
+			return
+		}
 	}
 }
 

internal/daemon/vm_authsync.go

@@ -86,6 +86,15 @@ func provisionAuthorizedKey(ctx context.Context, runner system.CommandRunner, im
 	return system.WriteExt4FileOwned(ctx, runner, imagePath, "/.ssh/authorized_keys", 0o600, 0, 0, merged)
 }
 
+// ensureHushLoginOnWorkDisk lands /root/.hushlogin in the guest by
+// writing /.hushlogin at the root of the work disk (which mounts at
+// /root inside the guest). pam_motd checks $HOME/.hushlogin and stays
+// silent when it exists — combined with sshd's PrintMotd no / PrintLastLog no
+// that suppresses the Debian-style banner on `banger vm run`.
+func (s *WorkspaceService) ensureHushLoginOnWorkDisk(ctx context.Context, vm *model.VMRecord) error {
+	return system.WriteExt4FileOwned(ctx, s.runner, vm.Runtime.WorkDiskPath, "/.hushlogin", 0o644, 0, 0, nil)
+}
+
 func (s *WorkspaceService) ensureGitIdentityOnWorkDisk(ctx context.Context, vm *model.VMRecord) error {
 	runner := s.runner
 	if runner == nil {

internal/daemon/vm_disk.go

@@ -50,11 +50,6 @@ func (s *VMService) patchRootOverlay(ctx context.Context, vm model.VMRecord, ima
 	builder.WriteFile(guestnet.ConfigPath, guestnet.ConfigFile(vm.Runtime.GuestIP, s.config.BridgeIP, s.config.DefaultDNS))
 	builder.WriteFile(guestnet.GuestScriptPath, []byte(guestnet.BootstrapScript()))
 	builder.WriteFile("/etc/ssh/sshd_config.d/99-banger.conf", sshdConfig)
-	// pam_motd reads /etc/motd + /etc/update-motd.d on Debian-family
-	// guests independent of sshd's PrintMotd. .hushlogin in $HOME tells
-	// pam_motd to stay quiet for that user — root is the only login on
-	// banger VMs, so a single file suffices.
-	builder.WriteFile("/root/.hushlogin", []byte{})
 	builder.DropMountTarget("/home")
 	builder.DropMountTarget("/var")
 	builder.AddMount(guestconfig.MountSpec{
@@ -169,9 +164,11 @@ func (s *VMService) ensureWorkDisk(ctx context.Context, vm *model.VMRecord, imag
 //     Banger VMs are short-lived sandboxes. The Debian-style MOTD
 //     ("Linux ... GNU/Linux comes with ABSOLUTELY NO WARRANTY …") and
 //     the "Last login" line are pure noise for `vm run -- echo hi`
-//     style invocations. Pair this with the .hushlogin written below
+//     style invocations. Pair this with the .hushlogin landed on the
-//     so pam_motd also stays silent on distros that read /etc/motd
+//     work disk (see ensureHushLoginOnWorkDisk) so pam_motd also stays
-//     through PAM rather than sshd.
+//     silent on distros that read /etc/motd through PAM rather than
+//     sshd. The work disk mounts at /root, so the file has to live on
+//     that disk — a write to the rootfs overlay would be shadowed.
 func sshdGuestConfig() string {
 	return strings.Join([]string{
 		"PermitRootLogin prohibit-password",

internal/daemon/vm_lifecycle.go

@@ -131,44 +131,27 @@ func (s *VMService) stopVMLocked(ctx context.Context, current model.VMRecord) (v
 		}
 		return vm, nil
 	}
-	pid := s.vmHandles(vm.ID).PID
 	op.stage("graceful_shutdown")
-	// Reach into the guest over SSH to force a sync + queue a poweroff
+	// Reach into the guest over SSH to force a sync + queue a poweroff.
-	// before falling back on FC's SendCtrlAltDel. The sync is what
+	// The sync is what keeps stop() from losing data: every dirty page
-	// keeps stop() from losing data: every dirty page the guest hasn't
+	// the guest hasn't flushed through virtio-blk to the work disk is
-	// flushed through virtio-blk to the work disk is written out
+	// written out before this RPC returns. Once sync completes,
-	// before this RPC returns. Without it, files freshly created via
+	// root.ext4 on the host is consistent and cleanupRuntime's SIGKILL
-	// `vm workspace prepare` can disappear across stop+start, because
+	// is safe — there is no benefit to waiting for the guest's
-	// the 10-second wait_for_exit window expires (FC doesn't exit on
+	// poweroff.target to finish, so we skip waitForExit entirely.
-	// SendCtrlAltDel — Debian routes ctrl-alt-del.target → reboot.target,
-	// not poweroff) and the fallback SIGKILL drops everything still
-	// in FC's userspace I/O path.
 	//
-	// `systemctl --no-block poweroff` is queued for the same reason
+	// When SSH is unreachable (broken sshd, network down, drifted host
-	// SendCtrlAltDel was here originally — it's how stop() asks the
+	// key) we drop straight to SIGKILL via cleanupRuntime. The
-	// guest to halt. That request is best-effort; FC may or may not
+	// previous fallback was SendCtrlAltDel + a 10-second wait for FC
-	// exit before the SIGKILL fallback fires. Either way, sync
+	// to exit, but on Debian ctrl+alt+del routes to reboot.target, so
-	// already ran, so the on-host root.ext4 is consistent regardless.
+	// FC never exits on it — the wait was always a wasted 10s. We pay
-	//
+	// the data-loss cost we already paid before (after the timeout
-	// SendCtrlAltDel survives as a fallback for guests where SSH
+	// expired the old code SIGKILLed too), but without the latency.
-	// itself is unreachable (broken sshd, network down, drifted host
-	// key); it doesn't fix the data-loss path, but it's the existing
-	// last-resort signal and is at least no worse than today.
 	if err := s.requestGuestPoweroff(ctx, vm); err != nil {
 		if s.logger != nil {
-			s.logger.Warn("guest ssh poweroff failed; falling back to ctrl+alt+del",
+			s.logger.Warn("guest ssh poweroff failed; SIGKILL without sync",
 				append(vmLogAttrs(vm), "error", err.Error())...)
 		}
-		if fallbackErr := s.net.sendCtrlAltDel(ctx, vm.Runtime.APISockPath); fallbackErr != nil {
-			return model.VMRecord{}, fallbackErr
-		}
-	}
-	op.stage("wait_for_exit", "pid", pid)
-	if err := s.net.waitForExit(ctx, pid, vm.Runtime.APISockPath, gracefulShutdownWait); err != nil {
-		if !errors.Is(err, errWaitForExitTimeout) {
-			return model.VMRecord{}, err
-		}
-		op.stage("graceful_shutdown_timeout", "pid", pid)
 	}
 	op.stage("cleanup_runtime")
 	if err := s.cleanupRuntime(ctx, vm, true); err != nil {
@@ -190,16 +173,16 @@ func (s *VMService) stopVMLocked(ctx context.Context, current model.VMRecord) (v
 // comment in stopVMLocked. Returns the dial / SSH error if the guest
 // is unreachable; the caller treats that as a fallback signal.
 //
-// Bounded by a hard 5-second SSH-dial timeout so a half-broken guest
+// Bounded by a hard 2-second SSH-dial timeout. A reachable guest on
-// doesn't extend the overall stop window past the existing
+// the host bridge dials in single-digit milliseconds; if we haven't
-// gracefulShutdownWait. If the dial doesn't succeed in that window we
+// connected in 2s the guest is effectively gone, so we fail fast and
-// surface an error and let the caller take the SendCtrlAltDel path.
+// let the caller SIGKILL rather than burning latency on a doomed dial.
 func (s *VMService) requestGuestPoweroff(ctx context.Context, vm model.VMRecord) error {
 	guestIP := strings.TrimSpace(vm.Runtime.GuestIP)
 	if guestIP == "" {
 		return errors.New("guest IP unknown")
 	}
-	dialCtx, cancel := context.WithTimeout(ctx, 5*time.Second)
+	dialCtx, cancel := context.WithTimeout(ctx, 2*time.Second)
 	defer cancel()
 	address := net.JoinHostPort(guestIP, "22")
 	client, err := guest.Dial(dialCtx, address, s.config.SSHKeyPath, s.layout.KnownHostsPath)

internal/daemon/vm_test.go

@@ -1592,7 +1592,7 @@ func TestDeleteStoppedNATVMDoesNotFailWithoutTapDevice(t *testing.T) {
 	}
 }
 
-func TestStopVMFallsBackToForcedCleanupAfterGracefulTimeout(t *testing.T) {
+func TestStopVMSIGKILLsWhenSSHUnreachable(t *testing.T) {
 	ctx := context.Background()
 	db := openDaemonStore(t)
 	apiSock := filepath.Join(t.TempDir(), "fc.sock")
@@ -1606,12 +1606,6 @@ func TestStopVMFallsBackToForcedCleanupAfterGracefulTimeout(t *testing.T) {
 		}
 	})
 
-	oldGracefulWait := gracefulShutdownWait
-	gracefulShutdownWait = 50 * time.Millisecond
-	t.Cleanup(func() {
-		gracefulShutdownWait = oldGracefulWait
-	})
-
 	vm := testVM("stubborn", "image-stubborn", "172.16.0.23")
 	vm.State = model.VMStateRunning
 	vm.Runtime.State = model.VMStateRunning
@@ -1622,8 +1616,6 @@ func TestStopVMFallsBackToForcedCleanupAfterGracefulTimeout(t *testing.T) {
 		scriptedRunner: &scriptedRunner{
 			t: t,
 			steps: []runnerStep{
-				sudoStep("", nil, "chmod", "600", apiSock),
-				sudoStep("", nil, "chown", "-h", fmt.Sprintf("%d:%d", os.Getuid(), os.Getgid()), apiSock),
 				{call: runnerCall{name: "pgrep", args: []string{"-n", "-f", apiSock}}, out: []byte(strconv.Itoa(fake.Process.Pid) + "\n")},
 				sudoStep("", nil, "kill", "-KILL", strconv.Itoa(fake.Process.Pid)),
 			},

scripts/install.sh

@@ -228,6 +228,7 @@ banger $TARGET_VERSION installed.
 Next steps:
   banger doctor                    # confirm host readiness
   banger vm run                    # boot a sandbox
+  banger ssh-config --install      # optional: enable 'ssh <name>.vm'
 
 Updates land via:
   banger update --check