Updates

packages/bare-os-booter/index.js

@@ -8,7 +8,7 @@ import { topicKey, parseMbr } from 'bare-os-protocol'
 import { SwarmDisk } from './lib/swarm-disk.js'
 import { runKernelFromSource, runBinCommand } from './lib/kernel-runner.js'
 import { createVfs } from './lib/vfs.js'
-import { execShellLine } from './lib/shell.js'
+import { execShellLine, syncBareOsExitStatusEnv } from './lib/shell.js'
 import { packageRootDir, defaultBootCorestorePath } from './lib/paths.js'
 import {
   createBareReadlineQuestion,
@@ -36,6 +36,7 @@ import {
   startBareInitd,
   registerKernelShutdownHook
 } from './lib/bare-initd.js'
+import { BARE_OS_CTX_API_VERSION } from './lib/bare-os-ctx-api.js'
 import './lib/bare-cron.js'
 
 const _pkg = packageRootDir(import.meta.url)
@@ -221,6 +222,7 @@ async function executeKernel(disk, store, swarm, initSource) {
     GID: '65534',
     GROUP: 'guest',
     BARE_OS_IDENTITY: 'guest',
+    BARE_OS_EXIT_STATUS: '0',
     0: 'bare-os'
   }
   /** @type {{ getMounts: () => Map<string, { drive: import('hyperdrive').default, writable: boolean }> }} */
@@ -234,6 +236,8 @@ async function executeKernel(disk, store, swarm, initSource) {
   let forceSessionEnd = false
   /** @type {Record<string, unknown>} */
   const ctx = {
+    /** Documented `ctx` contract version; bump in lib/bare-os-ctx-api.js when the surface changes. */
+    bareOsCtxApiVersion: BARE_OS_CTX_API_VERSION,
     disk,
     drive: disk.drive,
     personalDrive: disk.personalDrive,
@@ -359,10 +363,14 @@ async function executeKernel(disk, store, swarm, initSource) {
     if (exitMatch) {
       const ec =
         exitMatch[1] != null ? Number.parseInt(exitMatch[1], 10) : 0
-      ctx.requestBooterExit(Number.isFinite(ec) ? ec : 0)
+      const code = Number.isFinite(ec) ? ec : 0
+      ctx.exitCode = code
+      syncBareOsExitStatusEnv(ctx)
+      ctx.requestBooterExit(code)
       return 'exit'
     }
-    return await execShellLine(ctx, line)
+    const st = await execShellLine(ctx, line)
+    return st
   }
   ctx.readLine = async (prompt) => {
     if (forceSessionEnd) return null

packages/bare-os-booter/lib/bare-initd.js

@@ -84,6 +84,12 @@ export async function startBareInitd(ctx) {
 
 const KERNEL_LOG_REL = '.kernel/kernel.log'
 
+/** Max size before trimming older log bytes (best-effort). */
+const KERNEL_LOG_MAX_BYTES = 512 * 1024
+
+/** After trim, keep this many trailing bytes plus a notice line. */
+const KERNEL_LOG_KEEP_BYTES = 256 * 1024
+
 /**
  * Append one UTF-8 line to ~/.kernel/kernel.log (personal drive). Best-effort; never throws.
  * @param {Record<string, unknown>} ctx
@@ -106,7 +112,15 @@ async function appendKernelLog(ctx, kind, line) {
     const prev = await vfs.readFile(logPath)
     const ts = new Date().toISOString()
     const chunk = ctx.b4a.from(`[${ts}] [${kind}] ${line}\n`)
-    const merged = prev ? ctx.b4a.concat([prev, chunk]) : chunk
+    let merged = prev ? ctx.b4a.concat([prev, chunk]) : chunk
+    if (merged.length > KERNEL_LOG_MAX_BYTES) {
+      const start = Math.max(0, merged.length - KERNEL_LOG_KEEP_BYTES)
+      const tail = merged.subarray(start)
+      const notice = ctx.b4a.from(
+        `[${ts}] [bare-os] kernel.log truncated (kept last ${KERNEL_LOG_KEEP_BYTES} bytes)\n`
+      )
+      merged = ctx.b4a.concat([notice, tail])
+    }
     await vfs.writeFile(logPath, merged)
   } catch {
     /* ignore */

packages/bare-os-booter/lib/bare-os-ctx-api.js

@@ -0,0 +1,5 @@
+/**
+ * Semantic version of the booter `ctx` contract for custom kernels.
+ * Bump when adding/removing/renaming documented `ctx` fields or changing behavior.
+ */
+export const BARE_OS_CTX_API_VERSION = '1.0.0'

packages/bare-os-booter/lib/shell.js

@@ -30,6 +30,20 @@ function mergeChildExitCode(ctx, childCtx) {
   }
 }
 
+/** Env key mirroring last command exit status (POSIX `$?` parity). */
+export const BARE_OS_EXIT_STATUS_ENV = 'BARE_OS_EXIT_STATUS'
+
+/**
+ * Mirror `ctx.exitCode` into `ctx.vfs.env` so kernels and `echo $?` see last status.
+ * @param {Record<string, unknown>} ctx
+ */
+export function syncBareOsExitStatusEnv(ctx) {
+  const env = ctx.vfs?.env
+  if (!env || typeof env !== 'object') return
+  const n = Number(ctx.exitCode)
+  env[BARE_OS_EXIT_STATUS_ENV] = String(Number.isFinite(n) ? n : 0)
+}
+
 /** Max alias indirections (prevents cycles). */
 const MAX_ALIAS_DEPTH = 16
 
@@ -338,10 +352,19 @@ export function expandWord(s, env) {
           break
         }
         const name = s.slice(j + 2, end)
-        out += env[name] ?? ''
+        if (name === '?') {
+          out += env[BARE_OS_EXIT_STATUS_ENV] ?? '0'
+        } else {
+          out += env[name] ?? ''
+        }
         j = end + 1
         continue
       }
+      if (s[j + 1] === '?') {
+        out += env[BARE_OS_EXIT_STATUS_ENV] ?? '0'
+        j += 2
+        continue
+      }
       if (/[0-9]/.test(s[j + 1] ?? '')) {
         out += env[s[j + 1]] ?? ''
         j += 2
@@ -853,6 +876,7 @@ export async function execShellLine(ctx, line) {
       'shell: unsupported operator & (job control is not available)'
     )
     ctx.exitCode = 2
+    syncBareOsExitStatusEnv(ctx)
     return 'ok'
   }
 
@@ -860,7 +884,11 @@ export async function execShellLine(ctx, line) {
   for (const listTok of lists) {
     if (!listTok.length) continue
     const r = await execAndOrList(ctx, listTok)
-    if (r === 'exit') return 'exit'
+    if (r === 'exit') {
+      syncBareOsExitStatusEnv(ctx)
+      return 'exit'
+    }
   }
+  syncBareOsExitStatusEnv(ctx)
   return 'ok'
 }

packages/bare-os-booter/test.js

@@ -21,8 +21,11 @@ import {
   loadBarerc,
   BARERC_SKELETON,
   splitTokensBySemicolon,
-  splitTokensByAndOr
+  splitTokensByAndOr,
+  BARE_OS_EXIT_STATUS_ENV,
+  syncBareOsExitStatusEnv
 } from './lib/shell.js'
+import { BARE_OS_CTX_API_VERSION } from './lib/bare-os-ctx-api.js'
 import {
   fuzzyMatch,
   stripAnsi,
@@ -74,6 +77,7 @@ function testCtx(drive, personal, env) {
     UID: '1000',
     GID: '1000',
     PWD: '/home/user',
+    BARE_OS_EXIT_STATUS: '0',
     ...env
   }
   const vfs = createVfs(drive, personal, shellEnv)
@@ -455,6 +459,44 @@ test('expandWord reads env', async (t) => {
   t.is(expandWord('x${HOME}y', { HOME: '/h' }), 'x/hy')
 })
 
+test('expandWord $? and ${?} use BARE_OS_EXIT_STATUS', async (t) => {
+  const env = { [BARE_OS_EXIT_STATUS_ENV]: '7', HOME: '/h' }
+  t.is(expandWord('code=$?', env), 'code=7')
+  t.is(expandWord('c=${?}', env), 'c=7')
+  t.is(expandWord('missing=$?', {}), 'missing=0')
+})
+
+test('syncBareOsExitStatusEnv and execShellLine update env', async (t) => {
+  const dir = testCorestoreDir('exstat')
+  const store = new Corestore(dir)
+  const drive = new Hyperdrive(store)
+  const personal = new Hyperdrive(store.namespace('pex'))
+  await drive.ready()
+  await personal.ready()
+  await drive.put(
+    '/bin/false',
+    b4a.from(`async function run(ctx) { ctx.exitCode = 1 }`)
+  )
+  await drive.put(
+    '/bin/true',
+    b4a.from(`async function run(ctx) { ctx.exitCode = 0 }`)
+  )
+  const ctx = testCtx(drive, personal)
+  ctx.exitCode = 0
+  syncBareOsExitStatusEnv(ctx)
+  t.is(ctx.vfs.env[BARE_OS_EXIT_STATUS_ENV], '0')
+  await execShellLine(ctx, 'false')
+  t.is(ctx.vfs.env[BARE_OS_EXIT_STATUS_ENV], '1')
+  await execShellLine(ctx, 'true')
+  t.is(ctx.vfs.env[BARE_OS_EXIT_STATUS_ENV], '0')
+  await store.close()
+  rmSync(dir, { recursive: true, force: true })
+})
+
+test('BARE_OS_CTX_API_VERSION is semver-shaped', async (t) => {
+  t.ok(/^\d+\.\d+\.\d+$/.test(BARE_OS_CTX_API_VERSION))
+})
+
 test('expandArgvAliases expands first word and keeps trailing argv', async (t) => {
   t.alike(expandArgvAliases(['ll', 'z'], defaultShellAliases()), [
     'ls',

packages/bare-os-seeder/kernel/etc/bare-os/rc

@@ -0,0 +1,4 @@
+# Optional boot-time shell lines (one command per non-comment line).
+# Executed by /boot/init.js after /etc/os-release and this motd, before the main banner.
+# Example (uncomment to use):
+# export BARE_OS_SHOW_RC=1

packages/bare-os-seeder/kernel/etc/motd

@@ -0,0 +1 @@
+Welcome to Bare OS — edit /etc/motd on the system image to customize this line.