Ship initrd.img in MSI using build-time generation via powershell script (#14424)
* Ship initrd.img in MSI using build-time generation via tar.exe Replace the install-time CreateInitrd/RemoveInitrd custom actions with a build-time step that generates initrd.img using the Windows built-in tar.exe (libarchive/bsdtar) and ships it directly in the MSI. The install-time approach had a race condition: wsl.exe could launch before the CreateInitrd custom action completed, causing ERROR_FILE_NOT_FOUND for initrd.img. Changes: - Add CMake custom command to generate initrd.img via tar.exe --format=newc - Add initrd.img as a regular file in the MSI tools component - Remove CreateInitrd/RemoveInitrd custom actions from WiX, DllMain, and wslinstall.def - Remove CreateCpioInitrd helper and its tests (no longer needed) - Update pipeline build targets to build initramfs instead of init * pr feedback * more pr feedback * switch to using a powershell script instead of tar.exe * powershell script feedback * hopefully final pr feedback --------- Co-authored-by: Ben Hillis <benhill@ntdev.microsoft.com>
Ben Hillis committed
Mar 12, 2026 at 20:42 UTC
e5cb458e67b18bb8082f0b79a9f4b3978cf5451b
11 files changed
+82
-289
.pipelines/build-stage.yml
+1
-1
@@ -23,7 +23,7 @@ parameters:
23
- name: targets
24
type: object
25
default:
26
- - target: "wsl;libwsl;wslg;wslservice;wslhost;wslrelay;wslinstaller;wslinstall;init;wslserviceproxystub;wslsettings;wslinstallerproxystub;testplugin"
26
+ - target: "wsl;libwsl;wslg;wslservice;wslhost;wslrelay;wslinstaller;wslinstall;initramfs;wslserviceproxystub;wslsettings;wslinstallerproxystub;testplugin"
27
pattern: "wsl.exe,libwsl.dll,wslg.exe,wslservice.exe,wslhost.exe,wslrelay.exe,wslinstaller.exe,wslinstall.dll,wslserviceproxystub.dll,wslsettings/wslsettings.dll,wslsettings/wslsettings.exe,wslinstallerproxystub.dll,wsldevicehost.dll,WSLDVCPlugin.dll,testplugin.dll,wsldeps.dll"
28
- target: "msixgluepackage"
29
pattern: "gluepackage.msix"
msipackage/CMakeLists.txt
+2
-2
@@ -22,7 +22,7 @@ foreach(binary ${WINDOWS_BINARIES})
22
list(APPEND BINARIES_DEPENDENCIES "${PACKAGE_INPUT_DIR}/${binary}")
23
endforeach()
24
25
-set(LINUX_BINARIES init)
25
+set(LINUX_BINARIES init;initrd.img)
26
foreach(binary ${LINUX_BINARIES})
27
list(APPEND BINARIES_DEPENDENCIES "${BIN}/${binary}")
28
endforeach()
@@ -52,7 +52,7 @@ add_custom_command(
52
53
add_custom_target(msipackage DEPENDS ${OUTPUT_PACKAGE})
54
set_target_properties(msipackage PROPERTIES EXCLUDE_FROM_ALL FALSE SOURCES ${PACKAGE_WIX_IN})
55
-add_dependencies(msipackage wsl wslg wslservice wslhost wslrelay wslserviceproxystub init wslinstall msixgluepackage)
55
+add_dependencies(msipackage wsl wslg wslservice wslhost wslrelay wslserviceproxystub init initramfs wslinstall msixgluepackage)
56
57
if (WSL_BUILD_WSL_SETTINGS)
58
add_dependencies(msipackage wslsettings libwsl)
msipackage/package.wix.in
+1
-21
@@ -261,6 +261,7 @@
261
<DirectoryRef Id="TOOLSFOLDER">
262
<Component Id="tools" Guid="F0C8D6BA-1502-41E7-BF72-D93DFA134733" Bitness="always64" UninstallWhenSuperseded="yes">
263
<File Id="init" Source="${BIN}/init" Checksum="yes" />
264
+ <File Id="initrd.img" Source="${BIN}/initrd.img" Checksum="yes" />
265
<File Id="bsdtar" Source="${BSDTARD_SOURCE_DIR}/${TARGET_PLATFORM}/bsdtar"/>
266
267
<?if "${WSL_DEV_BINARY_PATH}" = "" ?>
@@ -461,21 +462,6 @@
462
Execute="deferred"
463
/>
464
464
- <CustomAction Id="CreateInitrd"
465
- Impersonate="no"
466
- BinaryRef="wslinstall.dll"
467
- DllEntry="CreateInitrd"
468
- Return="check"
469
- Execute="deferred"
470
- />
471
-
472
- <CustomAction Id="RemoveInitrd"
473
- Impersonate="no"
474
- BinaryRef="wslinstall.dll"
475
- DllEntry="RemoveInitrd"
476
- Return="check"
477
- Execute="deferred"
478
- />
465
466
<CustomAction Id="RemoveRegistryKeyProtections"
467
Impersonate="no"
@@ -540,16 +526,10 @@
526
<!-- This needs to run after the registry is written because this action needs to read the install path -->
527
<Custom Action="RegisterLspCategories" After="WriteRegistryValues" Condition='((not REMOVE~="ALL") or WIX_UPGRADE_DETECTED) and (not UPGRADINGPRODUCTCODE) and (not SKIPLSP = 1)' />
528
543
- <!-- Generate initrd.img from the init binary whenever the tools component is being installed -->
544
- <Custom Action="CreateInitrd" After="RegisterLspCategories" Condition='$tools=3' />
545
-
529
<!-- This needs to run before the registry is cleared because this action needs to read the install path.
530
This actions runs on uninstallation and upgrade. -->
531
<Custom Action="UnregisterLspCategories" Before="RemoveRegistryValues" Condition='(REMOVE~="ALL") and (not UPGRADINGPRODUCTCODE) and (not SKIPLSP = 1)' />
532
550
- <!-- Remove initrd.img during uninstallation. Must run after StopServices so the file isn't locked -->
551
- <Custom Action="RemoveInitrd" Before="UnregisterLspCategories" Condition='(REMOVE~="ALL") and (not UPGRADINGPRODUCTCODE)' />
552
-
533
<?if "${WSL_BUILD_WSL_SETTINGS}" = "true" ?>
534
<!-- This needs to run before the registry is written because this action calculates registry key names and values -->
535
<Custom Action="CalculateWslSettingsProtocolIds" Before="WriteRegistryValues" Condition='(not REMOVE~="ALL")' />
src/linux/init/CMakeLists.txt
+11
@@ -51,3 +51,14 @@ add_linux_executable(init "${SOURCES}" "${HEADERS};${COMMON_LINUX_HEADERS}" "${I
51
add_dependencies(init localization)
52
53
set_target_properties(init PROPERTIES FOLDER linux)
54
+
55
+set(INITRAMFS ${CMAKE_RUNTIME_OUTPUT_DIRECTORY}/${CMAKE_BUILD_TYPE}/initrd.img)
56
+set(INIT ${CMAKE_RUNTIME_OUTPUT_DIRECTORY}/${CMAKE_BUILD_TYPE}/init)
57
+add_custom_command(
58
+ OUTPUT ${INITRAMFS} "${CMAKE_CURRENT_BINARY_DIR}/CmakeFiles/initramfs"
59
+ DEPENDS init ${INIT}
60
+ COMMAND powershell.exe -ExecutionPolicy Bypass -NoProfile -NonInteractive -File "${CMAKE_SOURCE_DIR}/tools/create-initrd.ps1" "${INIT}" "${INITRAMFS}"
61
+ COMMAND ${CMAKE_COMMAND} -E touch "${CMAKE_CURRENT_BINARY_DIR}/CmakeFiles/initramfs"
62
+ VERBATIM)
63
+add_custom_target(initramfs DEPENDS ${INITRAMFS})
64
+set_target_properties(initramfs PROPERTIES FOLDER linux)
src/windows/common/filesystem.cpp
-112
@@ -1115,118 +1115,6 @@ void wsl::windows::common::filesystem::UpdateInit(_In_ PCWSTR BasePath, _In_ ULO
1115
CopyFileWithMetadata(source.c_str(), dest.c_str(), (LX_S_IFREG | 0755), DistroVersion);
1116
}
1117
1118
-void wsl::windows::common::filesystem::CreateCpioInitrd(_In_ const std::filesystem::path& SourcePath, _In_ const std::filesystem::path& DestPath)
1119
-{
1120
- // Open the source init binary
1121
- wil::unique_hfile sourceFile{
1122
- CreateFileW(SourcePath.c_str(), GENERIC_READ, FILE_SHARE_READ, nullptr, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, nullptr)};
1123
- THROW_LAST_ERROR_IF(!sourceFile);
1124
-
1125
- // Get file size
1126
- LARGE_INTEGER fileSize{};
1127
- THROW_IF_WIN32_BOOL_FALSE(GetFileSizeEx(sourceFile.get(), &fileSize));
1128
- THROW_HR_IF(E_INVALIDARG, fileSize.HighPart != 0); // File too large
1129
-
1130
- const DWORD initSize = fileSize.LowPart;
1131
- const auto initDataPadding = (4 - (initSize % 4)) % 4;
1132
- wil::unique_hfile destFile{CreateFileW(DestPath.c_str(), GENERIC_WRITE, 0, nullptr, CREATE_ALWAYS, FILE_ATTRIBUTE_NORMAL, nullptr)};
1133
- THROW_LAST_ERROR_IF(!destFile);
1134
-
1135
- // Clean up the destination file on failure.
1136
- auto deleteFile = wil::scope_exit_log(WI_DIAGNOSTICS_INFO, [&] {
1137
- destFile.reset();
1138
- LOG_IF_WIN32_BOOL_FALSE(DeleteFileW(DestPath.c_str()));
1139
- });
1140
-
1141
- auto writeCpioHeader = [&destFile](DWORD fileSize, PCSTR name) {
1142
- // CPIO newc header: magic(6) + 13 fields of 8 hex chars each = 110 bytes
1143
- constexpr size_t headerSize = 110;
1144
- const auto nameLen = strlen(name) + 1;
1145
- const auto headerPadding = (4 - ((headerSize + nameLen) % 4)) % 4;
1146
- const bool isTrailer = strcmp(name, "TRAILER!!!") == 0;
1147
-
1148
- // Get current time for mtime. CPIO newc format only supports 32-bit fields.
1149
- const auto mtime = static_cast<DWORD>(time(nullptr));
1150
-
1151
- char header[headerSize + 1];
1152
- sprintf_s(
1153
- header,
1154
- "070701" // magic
1155
- "%08X" // inode
1156
- "%08X" // mode
1157
- "%08X" // uid
1158
- "%08X" // gid
1159
- "%08X" // nlink
1160
- "%08X" // mtime
1161
- "%08X" // filesize
1162
- "%08X" // devmajor
1163
- "%08X" // devminor
1164
- "%08X" // rdevmajor
1165
- "%08X" // rdevminor
1166
- "%08X" // namesize
1167
- "%08X", // check
1168
- 0,
1169
- isTrailer ? 0 : 0100755,
1170
- 0,
1171
- 0,
1172
- isTrailer ? 0 : 1,
1173
- mtime,
1174
- fileSize,
1175
- 0,
1176
- 0,
1177
- 0,
1178
- 0,
1179
- static_cast<DWORD>(nameLen),
1180
- 0);
1181
-
1182
- DWORD bytesWritten;
1183
- THROW_IF_WIN32_BOOL_FALSE(WriteFile(destFile.get(), header, headerSize, &bytesWritten, nullptr));
1184
-
1185
- // Write name with null terminator
1186
- THROW_IF_WIN32_BOOL_FALSE(WriteFile(destFile.get(), name, static_cast<DWORD>(nameLen), &bytesWritten, nullptr));
1187
-
1188
- // Write padding to align to 4 bytes
1189
- if (headerPadding > 0)
1190
- {
1191
- char padding[4] = {0};
1192
- THROW_IF_WIN32_BOOL_FALSE(WriteFile(destFile.get(), padding, static_cast<DWORD>(headerPadding), &bytesWritten, nullptr));
1193
- }
1194
- };
1195
-
1196
- // Write init file header
1197
- writeCpioHeader(initSize, SourcePath.filename().string().c_str());
1198
-
1199
- // Copy file contents
1200
- wsl::windows::common::relay::InterruptableRelay(sourceFile.get(), destFile.get(), nullptr, 64 * 1024);
1201
-
1202
- // Write data padding
1203
- if (initDataPadding > 0)
1204
- {
1205
- char padding[4] = {0};
1206
- DWORD bytesWritten;
1207
- THROW_IF_WIN32_BOOL_FALSE(WriteFile(destFile.get(), padding, static_cast<DWORD>(initDataPadding), &bytesWritten, nullptr));
1208
- }
1209
-
1210
- // Write trailer entry (empty file with name "TRAILER!!!")
1211
- writeCpioHeader(0, "TRAILER!!!");
1212
-
1213
- // Pad the archive to 512-byte boundary
1214
- constexpr DWORD archiveBlockSize = 512;
1215
- LARGE_INTEGER currentPos{};
1216
- THROW_IF_WIN32_BOOL_FALSE(SetFilePointerEx(destFile.get(), {}, ¤tPos, FILE_CURRENT));
1217
-
1218
- const auto currentSize = static_cast<ULONGLONG>(currentPos.QuadPart);
1219
- const auto archivePadding = static_cast<DWORD>((archiveBlockSize - (currentSize % archiveBlockSize)) % archiveBlockSize);
1220
- if (archivePadding > 0)
1221
- {
1222
- char paddingBuffer[archiveBlockSize] = {0};
1223
- DWORD bytesWritten;
1224
- THROW_IF_WIN32_BOOL_FALSE(WriteFile(destFile.get(), paddingBuffer, archivePadding, &bytesWritten, nullptr));
1225
- }
1226
-
1227
- deleteFile.release();
1228
-}
1229
-
1118
wil::unique_hfile wsl::windows::common::filesystem::WipeAndOpenDirectory(_In_ LPCWSTR pPath)
1119
{
1120
const auto result = wil::RemoveDirectoryRecursiveNoThrow(pPath);
src/windows/common/filesystem.hpp
-5
@@ -228,11 +228,6 @@ std::wstring UnquotePath(_In_ LPCWSTR Path);
228
/// </summary>
229
void UpdateInit(_In_ PCWSTR BasePath, _In_ ULONG DistroVersion);
230
231
-/// <summary>
232
-/// Creates a CPIO newc format initrd archive from a single source file.
233
-/// </summary>
234
-void CreateCpioInitrd(_In_ const std::filesystem::path& SourcePath, _In_ const std::filesystem::path& DestPath);
235
-
231
/// <summary>
232
/// Wipes out the directory with the given path if it exists, then creates it again and returns
233
/// an open directory handle onto it.
src/windows/wslinstall/DllMain.cpp
-40
@@ -872,46 +872,6 @@ extern "C" UINT __stdcall UnregisterLspCategories(MSIHANDLE install)
872
return NOERROR;
873
}
874
875
-extern "C" UINT __stdcall CreateInitrd(MSIHANDLE install)
876
-try
877
-{
878
- WSL_INSTALL_LOG("CreateInitrd");
879
-
880
- const auto installRoot = wsl::windows::common::wslutil::GetMsiPackagePath();
881
- THROW_HR_IF(E_INVALIDARG, !installRoot.has_value());
882
-
883
- const auto toolsPath = std::filesystem::path(installRoot.value()) / LXSS_TOOLS_DIRECTORY;
884
- const auto initPath = toolsPath / L"init";
885
- const auto initrdPath = toolsPath / LXSS_VM_MODE_INITRD_NAME;
886
- wsl::windows::common::filesystem::CreateCpioInitrd(initPath, initrdPath);
887
-
888
- return NOERROR;
889
-}
890
-catch (...)
891
-{
892
- LOG_CAUGHT_EXCEPTION();
893
-
894
- return ERROR_INSTALL_FAILURE;
895
-}
896
-
897
-extern "C" UINT __stdcall RemoveInitrd(MSIHANDLE install)
898
-{
899
- try
900
- {
901
- WSL_INSTALL_LOG("RemoveInitrd");
902
-
903
- const auto installRoot = wsl::windows::common::wslutil::GetMsiPackagePath();
904
- THROW_HR_IF(E_INVALIDARG, !installRoot.has_value());
905
-
906
- const auto initrdPath = std::filesystem::path(installRoot.value()) / LXSS_TOOLS_DIRECTORY / LXSS_VM_MODE_INITRD_NAME;
907
- THROW_IF_WIN32_BOOL_FALSE(DeleteFileW(initrdPath.c_str()));
908
- }
909
- CATCH_LOG()
910
-
911
- // Failures in this method aren't fatal.
912
- return NOERROR;
913
-}
914
-
875
std::wstring GetWslSettingsInstalledExePath(MSIHANDLE install)
876
{
877
const auto wslSettingsInstallFolder = GetMsiProperty(install, c_wslSettingsInstalledDirectoryPropertyName);
src/windows/wslinstall/wslinstall.def
-2
@@ -4,8 +4,6 @@ EXPORTS
4
CleanExplorerState
5
CleanMsixState
6
DeprovisionMsix
7
- CreateInitrd
8
- RemoveInitrd
7
WslValidateInstallation
8
WslFinalizeInstallation
9
InstallMsix
test/windows/InstallerTests.cpp
-51
@@ -485,57 +485,6 @@ class InstallerTests
485
ValidatePackageInstalledProperly();
486
}
487
488
- TEST_METHOD(InitrdImgLifecycle)
489
- {
490
- // initrd.img is generated during installation from the init binary.
491
- // It should:
492
- // 1. Exist after a fresh install (generated by custom action)
493
- // 2. Be re-created when the component is upgraded
494
- // 3. Persist when reinstalling the same version
495
- // 4. Be removed on uninstall
496
-
497
- auto initrdPath = m_installedPath / L"tools" / L"initrd.img";
498
-
499
- // Uninstall and install an older version to get a clean state
500
- UninstallMsi();
501
- VERIFY_IS_FALSE(IsMsiPackageInstalled());
502
-
503
- // Case 1: Install older version (2.5.10 which ships initrd.img in the MSI)
504
- InstallGitHubRelease(L"2.5.10");
505
- VERIFY_IS_TRUE(IsMsiPackageInstalled());
506
- VERIFY_IS_TRUE(std::filesystem::exists(initrdPath), L"initrd.img should exist after installing 2.5.10");
507
- ValidatePackageInstalledProperly(L"2.5.10.0");
508
-
509
- // Case 2: Upgrade to current version - initrd.img should be regenerated by custom action
510
- InstallMsi();
511
- VERIFY_IS_TRUE(IsMsiPackageInstalled());
512
- VERIFY_IS_TRUE(std::filesystem::exists(initrdPath), L"initrd.img should exist after upgrade (generated by installer)");
513
- ValidatePackageInstalledProperly();
514
-
515
- // Case 3: Reinstall same version - initrd.img should persist
516
- InstallMsi();
517
- VERIFY_IS_TRUE(IsMsiPackageInstalled());
518
- VERIFY_IS_TRUE(std::filesystem::exists(initrdPath), L"initrd.img should exist after reinstalling same version");
519
- ValidatePackageInstalledProperly();
520
-
521
- // Case 4: Downgrade to older version
522
- InstallGitHubRelease(L"2.5.10");
523
- VERIFY_IS_TRUE(IsMsiPackageInstalled());
524
- VERIFY_IS_TRUE(std::filesystem::exists(initrdPath), L"initrd.img should exist after downgrade");
525
- ValidatePackageInstalledProperly(L"2.5.10.0");
526
-
527
- // Case 5: Uninstall - initrd.img should be removed
528
- UninstallMsi();
529
- VERIFY_IS_FALSE(IsMsiPackageInstalled());
530
- VERIFY_IS_FALSE(std::filesystem::exists(initrdPath), L"initrd.img should be removed on uninstall");
531
-
532
- // Reinstall to leave the system in a consistent state for other tests
533
- InstallMsi();
534
- VERIFY_IS_TRUE(IsMsiPackageInstalled());
535
- VERIFY_IS_TRUE(std::filesystem::exists(initrdPath), L"initrd.img should exist after fresh install");
536
- ValidatePackageInstalledProperly();
537
- }
538
-
488
TEST_METHOD(UpgradeInstallsTheMsiPackage)
489
{
490
// Remove the MSIX package
test/windows/SimpleTests.cpp
-55
@@ -296,60 +296,5 @@ class SimpleTests
296
VERIFY_IS_TRUE(output.find(L"/mnt/c/Program Files (x86)/Common Files") != std::wstring::npos);
297
VERIFY_IS_TRUE(output.find(L"/mnt/c/Users/Test User/AppData/Local/Programs/Microsoft VS Code/bin") != std::wstring::npos);
298
}
299
-
300
- TEST_METHOD(CreateCpioInitrd)
301
- {
302
- using wsl::windows::common::filesystem::CreateCpioInitrd;
303
- using wsl::windows::common::filesystem::TempFile;
304
- using wsl::windows::common::filesystem::TempFileFlags;
305
-
306
- auto validateCpio = [](size_t sourceSize) {
307
- // Create source file with specified size
308
- TempFile sourceFile(GENERIC_WRITE, 0, CREATE_ALWAYS, TempFileFlags::None);
309
- std::vector<char> sourceData(sourceSize, 'X');
310
- DWORD written;
311
- THROW_IF_WIN32_BOOL_FALSE(
312
- WriteFile(sourceFile.Handle.get(), sourceData.data(), static_cast<DWORD>(sourceData.size()), &written, nullptr));
313
- sourceFile.Handle.reset();
314
-
315
- // Create CPIO archive
316
- TempFile destFile(0, 0, CREATE_ALWAYS, TempFileFlags::None, L"img");
317
- CreateCpioInitrd(sourceFile.Path, destFile.Path);
318
-
319
- // Read and validate the CPIO archive
320
- wil::unique_hfile cpioHandle{CreateFileW(
321
- destFile.Path.c_str(), GENERIC_READ, FILE_SHARE_READ, nullptr, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, nullptr)};
322
- THROW_LAST_ERROR_IF(!cpioHandle);
323
-
324
- LARGE_INTEGER cpioSize{};
325
- THROW_IF_WIN32_BOOL_FALSE(GetFileSizeEx(cpioHandle.get(), &cpioSize));
326
- VERIFY_ARE_EQUAL(cpioSize.QuadPart % 512, 0LL); // Archive padded to 512-byte boundary
327
-
328
- char header[111] = {};
329
- DWORD bytesRead;
330
- THROW_IF_WIN32_BOOL_FALSE(ReadFile(cpioHandle.get(), header, 110, &bytesRead, nullptr));
331
- VERIFY_ARE_EQUAL(bytesRead, 110u);
332
-
333
- // Parse CPIO newc header: magic(6) ino mode uid gid nlink mtime filesize devmajor devminor rdevmajor rdevminor namesize check
334
- DWORD fileSize, nameSize;
335
- VERIFY_ARE_EQUAL(sscanf_s(header, "070701%*8x%*8x%*8x%*8x%*8x%*8x%8x%*8x%*8x%*8x%*8x%8x", &fileSize, &nameSize), 2);
336
-
337
- // Verify filename matches source file
338
- auto expectedName = sourceFile.Path.filename().string();
339
- VERIFY_ARE_EQUAL(nameSize, static_cast<DWORD>(expectedName.size() + 1));
340
-
341
- std::string filename(nameSize, '\0');
342
- THROW_IF_WIN32_BOOL_FALSE(ReadFile(cpioHandle.get(), filename.data(), nameSize, &bytesRead, nullptr));
343
- VERIFY_ARE_EQUAL(filename.c_str(), expectedName);
344
-
345
- VERIFY_ARE_EQUAL(fileSize, static_cast<DWORD>(sourceSize));
346
- };
347
-
348
- // Test various sizes to exercise 4-byte alignment padding
349
- for (size_t size : {0, 1, 2, 3, 4, 5, 100, 1024, 4096, 65536})
350
- {
351
- validateCpio(size);
352
- }
353
- }
299
};
300
} // namespace SimpleTests
\ No newline at end of file
tools/create-initrd.ps1
new
+67
@@ -0,0 +1,67 @@
1
+# Copyright (c) Microsoft Corporation.
2
+# Licensed under the MIT License.
3
+
4
+# Creates a CPIO newc format initramfs archive containing a single file named "init"
5
+# with mode 0100755 (rwxr-xr-x), uid 0, gid 0.
6
+
7
+[CmdletBinding()]
8
+param (
9
+ [Parameter(Mandatory)][string]$InputFile,
10
+ [Parameter(Mandatory)][string]$OutputFile
11
+)
12
+
13
+$ErrorActionPreference = "Stop"
14
+Set-StrictMode -Version Latest
15
+
16
+function Write-Pad([System.IO.Stream]$Stream)
17
+{
18
+ $remainder = $Stream.Position % 4
19
+ if ($remainder -ne 0)
20
+ {
21
+ $pad = [byte[]]::new(4 - $remainder)
22
+ $Stream.Write($pad, 0, $pad.Length)
23
+ }
24
+}
25
+
26
+function Write-CpioEntry([System.IO.Stream]$Stream, [byte[]]$NameBytes, [byte[]]$FileData, [int]$Mode, [uint32]$Mtime)
27
+{
28
+ $header = "070701" + # header magic
29
+ "00000001" + # inode
30
+ ("{0:X8}" -f $Mode) + # mode
31
+ "00000000" + # uid
32
+ "00000000" + # gid
33
+ "00000001" + # nlink
34
+ ("{0:X8}" -f $Mtime) + # mtime
35
+ ("{0:X8}" -f $FileData.Length) + # filesize
36
+ "00000000" + # devmajor
37
+ "00000000" + # devminor
38
+ "00000000" + # rdevmajor
39
+ "00000000" + # rdevminor
40
+ ("{0:X8}" -f $NameBytes.Length) + # namesize
41
+ "00000000" # check
42
+ $headerBytes = [System.Text.Encoding]::ASCII.GetBytes($header)
43
+ $Stream.Write($headerBytes, 0, $headerBytes.Length)
44
+ $Stream.Write($NameBytes, 0, $NameBytes.Length)
45
+ Write-Pad $Stream
46
+ if ($FileData.Length -gt 0)
47
+ {
48
+ $Stream.Write($FileData, 0, $FileData.Length)
49
+ Write-Pad $Stream
50
+ }
51
+}
52
+
53
+$data = [System.IO.File]::ReadAllBytes($InputFile)
54
+$name = [System.Text.Encoding]::ASCII.GetBytes("init`0")
55
+$mtime = [uint32][System.DateTimeOffset]::UtcNow.ToUnixTimeSeconds()
56
+
57
+$out = [System.IO.File]::Create($OutputFile)
58
+try
59
+{
60
+ Write-CpioEntry $out $name $data 0x81ED $mtime # S_IFREG | 0755
61
+ $trailer = [System.Text.Encoding]::ASCII.GetBytes("TRAILER!!!`0")
62
+ Write-CpioEntry $out $trailer ([byte[]]::new(0)) 0 0
63
+}
64
+finally
65
+{
66
+ $out.Close()
67
+}