docs/chromeos_build_instructions.md - chromium/src - Git at Google

 # Chrome OS Build Instructions

 Chrome for Chromium OS can be built in a couple different ways. After following
 the [initial setup](#common-setup), you'll need to choose one of the following
 build configurations:

 - If you're interested in testing Chrome OS code in Chrome, but not interactions
   with Chrome OS services, you can build for
   [linux-chromeos](#Chromium-OS-on-Linux-linux_chromeos) using just a Linux
   workstation.
 - Otherwise, Chrome's full integration can be covered by building for a real
   Chrome OS device or VM using [Simple Chrome](#Chromium-OS-Device-Simple-Chrome).
 - Use `is_chromeos_device` in GN and `BUILDFLAG(IS_CHROMEOS_DEVICE)` in C++ code
   to differentiate between these two modes.

 [TOC]

 ## Common setup

 First, follow the [normal Linux build
 instructions](https://chromium.googlesource.com/chromium/src/+/main/docs/linux/build_instructions.md)
 as usual to get a Chromium checkout.

 You'll also need to add `'chromeos'` to the `target_os` list in your `.gclient`
 configuration, which will fetch the additional build dependencies required for
 CrOS. This file is located one level up from your Chromium checkout's `src`.

 If you don't already have a `target_os` line present, simply add this to the
 end of the `.gclient` file:

     target_os = ['chromeos']

 If you already have a `target_os` line present in your `.gclient file`, you can
 simply append `'chromeos'` to the existing list there. For example:

     target_os = ['android', 'chromeos']

 Once your `.gclient` file is updated, you will need to run `gclient sync` once
 before proceeding with the rest of these instructions.

 ## Chromium OS on Linux (linux-chromeos)

 Chromium on Chromium OS uses Linux Chromium as a base, but adds a large number
 of Chrome OS-specific features to the code. For example, the login UI, window
 manager and system UI are part of the Chromium code base and built into the
 chrome binary.

 Fortunately, most Chromium changes that affect Chromium OS can be built and
 tested on a Linux workstation. This build is called "linux-chromeos". In this
 configuration most system services (like the power manager, bluetooth daemon,
 etc.) are stubbed out. The entire system UI runs in a single X11 window on your
 desktop.

 You can test sign-in/sync in this mode by adding the --login-manager flag, see
 the [Login notes](#Login-notes) section.

 ### Building and running Chromium with Chromium OS UI on your local machine

 Run the following in your chromium checkout:

     $ gn gen out/Default --args='target_os="chromeos"'
     $ autoninja -C out/Default chrome
     $ out/Default/chrome --use-system-clipboard

 (`autoninja` is a wrapper that automatically provides optimal values for the
 arguments passed to `ninja`).

 Some additional options you may wish to set by passing in `--args` to `gn gen`
 or running `gn args out/Default`:

     # Googlers: Reclient is a distributed compiler service. Goma successor.
     use_remoteexec = true

     is_component_build = true  # Links faster.
     is_debug = false           # Release build, runs faster.
     dcheck_always_on = true    # Enables DCHECK despite release build.
     enable_nacl = false        # Skips native client build, compiles faster.

     # Builds Chrome instead of Chromium. This requires a src-internal
     # checkout. Adds internal features and branded art assets.
     is_chrome_branded = true

     # Enables many optimizations, leading to much slower compiles, links,
     # and no runtime stack traces.
     #
     # Note: not compatible with `is_component_build = true`.
     is_official_build = true

 NOTE: You may wish to replace 'Default' with something like 'Cros' if
 you switch back and forth between Linux and Chromium OS builds, or 'Debug'
 if you want to differentiate between Debug and Release builds (see below).

 See [GN Build Configuration](https://www.chromium.org/developers/gn-build-configuration)
 for more information about configuring your build.

 You can also build and run test targets like `unit_tests`, `browser_tests`, etc.

 ### Flags

 Some useful flags:

 *    `--ash-debug-shortcuts`: Enable shortcuts such as Ctl+Alt+Shift+T to toggle
      tablet mode.
 *    `--ash-host-window-bounds="0+0-800x600,800+0-800x600"`: Specify one or more
      virtual screens, by display position and size.
 *    `--enable-features=Feature1,OtherFeature2`: Enable specified features.
      Features are often listed in chrome://flags, or in source files such as
      [chrome_features.cc](https://source.chromium.org/chromium/chromium/src/+/main:chrome/common/chrome_features.cc)
      or [ash_features.cc](https://source.chromium.org/chromium/chromium/src/+/main:ash/constants/ash_features.cc).
      Note that changing values in chrome://flags does not work for
      linux-chromeos, and this flag must be used.
 *    `--enable-ui-devtools[=9223]`: Allow debugging of the system UI through
      devtools either within linux-chromeos at chrome://inspect, or from a remote
      browser at
      devtools://devtools/bundled/devtools_app.html?uiDevTools=true&ws=127.0.0.1:9223/0
 *    `--remote-debugging-port=9222`: Allow debugging through devtools at
      http://localhost:9222
 *    `--use-system-clipboard`: Integrate clipboard with the host X11 system.

 ### Login notes

 By default this build signs in with a stub user. To specify a real user:

 *   For first run, add the following options to chrome's command line:
     `--user-data-dir=/tmp/chrome --login-manager`
 *   Go through the out-of-the-box UX and sign in with a real Gmail account.
 *   For subsequent runs, if you want to skip the login manager page, add:
     `--user-data-dir=/tmp/chrome --login-user=username@gmail.com
     --login-profile=username@gmail.com-hash`. It's also fine to just keep
     --login-manager instead.
 *   To run in guest mode instantly, add:
     `--user-data-dir=/tmp/chrome --bwsi --incognito --login-user='$guest'
     --login-profile=user`

 Signing in as a specific user is useful for debugging features like sync
 that require a logged in user.

 ### Graphics notes

 The Chromium OS build requires a functioning GL so if you plan on
 testing it through Chromium Remote Desktop you might face drawing
 problems (e.g. Aura window not painting anything). Possible remedies:

 *   `--ui-enable-software-compositing --ui-disable-threaded-compositing`
 *   `--use-gl=angle --use-angle=swiftshader`, but it's slow.

 To more closely match the UI used on devices, you can install fonts used
 by Chrome OS, such as Roboto, on your Linux distro.

 ## Chromium OS Device (Simple Chrome)

 This configuration allows you to build a fully functional Chrome for a real
 Chrome OS device or VM. Since Chrome OS uses a different toolchain for each
 device model, you'll first need to know the name of the model (or "board") you
 want to build for. For most boards, `amd64-generic` and `arm-generic` will
 produce a functional binary, though it won't be optimized and may be missing
 functionality.

 ### Additional gclient setup

 Each board has its own toolchain and misc. build dependencies. To fetch these,
 list the board under the `"cros_boards"` gclient custom var. If you were using
 the `amd64-generic` board, your `.gclient` file would look like:
 ```
 solutions = [
   {
     "url": "https://chromium.googlesource.com/chromium/src.git",
     "name": "src",
     "custom_deps": {},
     "custom_vars" : {
         "cros_boards": "amd64-generic",
     },
   },
 ]
 target_os = ["chromeos"]
 ```
 Once your .gclient file is updated, you will need to run `gclient sync` again
 to fetch the toolchain.

 NOTE:
  - If you'd like a VM image additionally downloaded for the board, add it to the
    `"cros_boards_with_qemu_images"` gclient custom var. That var downloads the
    SDK along with a VM image. `cros_boards` downloads only the SDK.
  - If you'd like to fetch multiple boards, add a `:` between each board in the
    gclient var. For example: `"cros_boards": "amd64-generic:arm-generic"`.

 ### Building for the board

 After the needed toolchain has been downloaded for your ${BOARD}, a build dir
 will have been conveniently created for you at `out_$BOARD/Release`, which can
 then be used to build Chrome. For the `amd64-generic` board, this would
 look like:

     $ gn gen out_amd64-generic/Release
     $ autoninja -C out_$BOARD/Release chrome

 Or if you prefer to use your own build dir, simply add the following line to the
 top of your GN args: `import("//build/args/chromeos/amd64-generic.gni")`. eg:

     $ gn gen out/Default --args='import("//build/args/chromeos/amd64-generic.gni")'
     $ autoninja -C out/Default chrome

 That will produce a Chrome OS build of Chrome very similar to what is shipped
 for that device. You can also supply additional args or even overwrite ones
 supplied in the imported .gni file after the `import()` line.

 ### Additional notes

 For more information (like copying the locally-built Chrome to a device, or
 running Tast tests), consult Simple Chrome's
 [full documentation](https://chromium.googlesource.com/chromiumos/docs/+/main/simple_chrome_workflow.md).
	# Chrome OS Build Instructions

	Chrome for Chromium OS can be built in a couple different ways. After following
	the [initial setup](#common-setup), you'll need to choose one of the following
	build configurations:

	- If you're interested in testing Chrome OS code in Chrome, but not interactions
	with Chrome OS services, you can build for
	[linux-chromeos](#Chromium-OS-on-Linux-linux_chromeos) using just a Linux
	workstation.
	- Otherwise, Chrome's full integration can be covered by building for a real
	Chrome OS device or VM using [Simple Chrome](#Chromium-OS-Device-Simple-Chrome).
	- Use `is_chromeos_device` in GN and `BUILDFLAG(IS_CHROMEOS_DEVICE)` in C++ code
	to differentiate between these two modes.

	[TOC]

	## Common setup

	First, follow the [normal Linux build
	instructions](https://chromium.googlesource.com/chromium/src/+/main/docs/linux/build_instructions.md)
	as usual to get a Chromium checkout.

	You'll also need to add `'chromeos'` to the `target_os` list in your `.gclient`
	configuration, which will fetch the additional build dependencies required for
	CrOS. This file is located one level up from your Chromium checkout's `src`.

	If you don't already have a `target_os` line present, simply add this to the
	end of the `.gclient` file:

	target_os = ['chromeos']

	If you already have a `target_os` line present in your `.gclient file`, you can
	simply append `'chromeos'` to the existing list there. For example:

	target_os = ['android', 'chromeos']

	Once your `.gclient` file is updated, you will need to run `gclient sync` once
	before proceeding with the rest of these instructions.

	## Chromium OS on Linux (linux-chromeos)

	Chromium on Chromium OS uses Linux Chromium as a base, but adds a large number
	of Chrome OS-specific features to the code. For example, the login UI, window
	manager and system UI are part of the Chromium code base and built into the
	chrome binary.

	Fortunately, most Chromium changes that affect Chromium OS can be built and
	tested on a Linux workstation. This build is called "linux-chromeos". In this
	configuration most system services (like the power manager, bluetooth daemon,
	etc.) are stubbed out. The entire system UI runs in a single X11 window on your
	desktop.

	You can test sign-in/sync in this mode by adding the --login-manager flag, see
	the [Login notes](#Login-notes) section.

	### Building and running Chromium with Chromium OS UI on your local machine

	Run the following in your chromium checkout:

	$ gn gen out/Default --args='target_os="chromeos"'
	$ autoninja -C out/Default chrome
	$ out/Default/chrome --use-system-clipboard

	(`autoninja` is a wrapper that automatically provides optimal values for the
	arguments passed to `ninja`).

	Some additional options you may wish to set by passing in `--args` to `gn gen`
	or running `gn args out/Default`:

	# Googlers: Reclient is a distributed compiler service. Goma successor.
	use_remoteexec = true

	is_component_build = true # Links faster.
	is_debug = false # Release build, runs faster.
	dcheck_always_on = true # Enables DCHECK despite release build.
	enable_nacl = false # Skips native client build, compiles faster.

	# Builds Chrome instead of Chromium. This requires a src-internal
	# checkout. Adds internal features and branded art assets.
	is_chrome_branded = true

	# Enables many optimizations, leading to much slower compiles, links,
	# and no runtime stack traces.
	#
	# Note: not compatible with `is_component_build = true`.
	is_official_build = true

	NOTE: You may wish to replace 'Default' with something like 'Cros' if
	you switch back and forth between Linux and Chromium OS builds, or 'Debug'
	if you want to differentiate between Debug and Release builds (see below).

	See [GN Build Configuration](https://www.chromium.org/developers/gn-build-configuration)
	for more information about configuring your build.

	You can also build and run test targets like `unit_tests`, `browser_tests`, etc.

	### Flags

	Some useful flags:

	* `--ash-debug-shortcuts`: Enable shortcuts such as Ctl+Alt+Shift+T to toggle
	tablet mode.
	* `--ash-host-window-bounds="0+0-800x600,800+0-800x600"`: Specify one or more
	virtual screens, by display position and size.
	* `--enable-features=Feature1,OtherFeature2`: Enable specified features.
	Features are often listed in chrome://flags, or in source files such as
	[chrome_features.cc](https://source.chromium.org/chromium/chromium/src/+/main:chrome/common/chrome_features.cc)
	or [ash_features.cc](https://source.chromium.org/chromium/chromium/src/+/main:ash/constants/ash_features.cc).
	Note that changing values in chrome://flags does not work for
	linux-chromeos, and this flag must be used.
	* `--enable-ui-devtools[=9223]`: Allow debugging of the system UI through
	devtools either within linux-chromeos at chrome://inspect, or from a remote
	browser at
	devtools://devtools/bundled/devtools_app.html?uiDevTools=true&ws=127.0.0.1:9223/0
	* `--remote-debugging-port=9222`: Allow debugging through devtools at
	http://localhost:9222
	* `--use-system-clipboard`: Integrate clipboard with the host X11 system.

	### Login notes

	By default this build signs in with a stub user. To specify a real user:

	* For first run, add the following options to chrome's command line:
	`--user-data-dir=/tmp/chrome --login-manager`
	* Go through the out-of-the-box UX and sign in with a real Gmail account.
	* For subsequent runs, if you want to skip the login manager page, add:
	`--user-data-dir=/tmp/chrome --login-user=username@gmail.com
	--login-profile=username@gmail.com-hash`. It's also fine to just keep
	--login-manager instead.
	* To run in guest mode instantly, add:
	`--user-data-dir=/tmp/chrome --bwsi --incognito --login-user='$guest'
	--login-profile=user`

	Signing in as a specific user is useful for debugging features like sync
	that require a logged in user.

	### Graphics notes

	The Chromium OS build requires a functioning GL so if you plan on
	testing it through Chromium Remote Desktop you might face drawing
	problems (e.g. Aura window not painting anything). Possible remedies:

	* `--ui-enable-software-compositing --ui-disable-threaded-compositing`
	* `--use-gl=angle --use-angle=swiftshader`, but it's slow.

	To more closely match the UI used on devices, you can install fonts used
	by Chrome OS, such as Roboto, on your Linux distro.

	## Chromium OS Device (Simple Chrome)

	This configuration allows you to build a fully functional Chrome for a real
	Chrome OS device or VM. Since Chrome OS uses a different toolchain for each
	device model, you'll first need to know the name of the model (or "board") you
	want to build for. For most boards, `amd64-generic` and `arm-generic` will
	produce a functional binary, though it won't be optimized and may be missing
	functionality.

	### Additional gclient setup

	Each board has its own toolchain and misc. build dependencies. To fetch these,
	list the board under the `"cros_boards"` gclient custom var. If you were using
	the `amd64-generic` board, your `.gclient` file would look like:
	```
	solutions = [
	{
	"url": "https://chromium.googlesource.com/chromium/src.git",
	"name": "src",
	"custom_deps": {},
	"custom_vars" : {
	"cros_boards": "amd64-generic",
	},
	},
	]
	target_os = ["chromeos"]
	```
	Once your .gclient file is updated, you will need to run `gclient sync` again
	to fetch the toolchain.

	NOTE:
	- If you'd like a VM image additionally downloaded for the board, add it to the
	`"cros_boards_with_qemu_images"` gclient custom var. That var downloads the
	SDK along with a VM image. `cros_boards` downloads only the SDK.
	- If you'd like to fetch multiple boards, add a `:` between each board in the
	gclient var. For example: `"cros_boards": "amd64-generic:arm-generic"`.

	### Building for the board

	After the needed toolchain has been downloaded for your ${BOARD}, a build dir
	will have been conveniently created for you at `out_$BOARD/Release`, which can
	then be used to build Chrome. For the `amd64-generic` board, this would
	look like:

	$ gn gen out_amd64-generic/Release
	$ autoninja -C out_$BOARD/Release chrome

	Or if you prefer to use your own build dir, simply add the following line to the
	top of your GN args: `import("//build/args/chromeos/amd64-generic.gni")`. eg:

	$ gn gen out/Default --args='import("//build/args/chromeos/amd64-generic.gni")'
	$ autoninja -C out/Default chrome

	That will produce a Chrome OS build of Chrome very similar to what is shipped
	for that device. You can also supply additional args or even overwrite ones
	supplied in the imported .gni file after the `import()` line.

	### Additional notes

	For more information (like copying the locally-built Chrome to a device, or
	running Tast tests), consult Simple Chrome's
	[full documentation](https://chromium.googlesource.com/chromiumos/docs/+/main/simple_chrome_workflow.md).