crouton: Chromium OS Universal Chroot Environment

crouton is a set of scripts that bundle up into an easy-to-use, Chromium OS-centric chroot generator. Currently Ubuntu and Debian are supported (using debootstrap behind the scenes), but "Chromium OS Debian, Ubuntu, and Probably Other Distros Eventually Chroot Environment" doesn't acronymize as well (crodupodece is admittedly pretty fun to say, though).

crouton is now maintenance-only

This means that:

• Only bugfix and release list PRs will be accepted.
• New distro releases will be added to the list as unsupported.
• As xenial is EOL, crouton will (at some point) no longer have a default release. You will always have to specify -r.
• Bugs without updates in the past year will be bulk-closed with a "stale" tag.
• Open PRs will be left open but have the "stale" tag added. If anyone who forks crouton wants to pick up the feature work, they can build right off of those PRs.
• For the safety of users and stability of crouton's functionality for those on EOL devices, offers to take over the dnschneid/crouton repo or Chrome extension will be declined, and requests to change link destinations will be rejected. If you would like to continue feature work on crouton, fork it, do a good job of it, and people can choose to use it at their own risk.

But first...

:warning: Steps to install crouton have changed! :warning:

Chromium OS has introduced several security features over the years that impede the installation and usage of crouton. If your device is no longer receiving updates, the steps below will likely work for you. However, if you are still having trouble, please try the community-maintained instructions.

In addition, goo.gl is going away! That means the fd3zc you know and love will eventually be replaced with git.io/JZEs0. That's a zero at the end, if you were wondering. Both just point to github, so you can always just memorize the full link instead, which (fun fact) does not include any numbers at all!

"crouton"...an acronym?

It stands for ChRomium Os Universal chrooT envirONment ...or something like that. Do capitals really matter if caps-lock has been (mostly) banished, and the keycaps are all lower-case?

Moving on...

Who's this for?

Anyone who wants to run straight Linux on their Chromium OS device, and doesn't care about physical security. You're also better off having some knowledge of Linux tools and the command line in case things go funny, but it's not strictly necessary.

What's a chroot?

Like virtualization, chroots provide the guest OS with their own, segregated file system to run in, allowing applications to run in a different binary environment from the host OS. Unlike virtualization, you are not booting a second OS; instead, the guest OS is running using the Chromium OS system. The benefit to this is that there is zero speed penalty since everything is run natively, and you aren't wasting RAM to boot two OSes at the same time. The downside is that you must be running the correct chroot for your hardware, the software must be compatible with Chromium OS's kernel, and machine resources are inextricably tied between the host Chromium OS and the guest OS. What this means is that while the chroot cannot directly access files outside of its view, it can access all of your hardware devices, including the entire contents of memory. A root exploit in your guest OS will essentially have unfettered access to the rest of Chromium OS.

...but hey, you can run TuxRacer!

What about dem crostinis though?

Crostini is an official project within Chromium OS to bring the Linux shell and apps to the platform in verified mode with clean integration, multi-layered security, and all the polish you expect from Chromium OS proper.

That means compared to crouton, Crostini has official support, competent engineers, and code that looks a little less like ramen. crouton, in its defense, has wider device compatibility, enables direct hardware access, and is named after an objectively tastier bread-based food item.

There's a solid community on Reddit if you'd like to try Crostini out. If it works for you -- great! No hard feelings. If in the end you decide that crouton suits you better, read on!

Note: you can't get the best of both worlds by installing crouton inside of Crostini. The technology (and life itself) just doesn't work that way. Not to mention a crouton Crostini would look ridiculous and be impossible to eat without getting bits everywhere.

Prerequisites

You need a device running Chromium OS that has been switched to developer mode.

For instructions on how to do that, go to this Chromium OS wiki page, click on your device model and follow the steps in the Entering Developer Mode section.

Note that developer mode, in its default configuration, is completely insecure, so don't expect a password in your chroot to keep anyone from your data. crouton does support encrypting chroots, but the encryption is only as strong as the quality of your passphrase. Consider this your warning.

It's also highly recommended that you install the crouton extension, which, when combined with the extension or xiwi targets, provides much improved integration with Chromium OS.

That's it! Surprised?

Usage

crouton is a powerful tool, and there are a lot of features, but basic usage is as simple as possible by design.

If you're just here to use crouton, you can grab the latest release from https://goo.gl/fd3zc?si=1. Download it, pop open a shell (Ctrl+Alt+T, type shell and hit enter), make the installer executable with sudo install -Dt /usr/local/bin -m 755 ~/Downloads/crouton, then launch it with sudo crouton to see the help text. See the "examples" section for some usage examples.

If you're modifying crouton, you'll probably want to clone or download the repo into a subdirectory of /usr/local and then either run installer/main.sh directly, or use make to build your very own crouton. You can also download the latest release, install it as above and run crouton -x to extract out the juicy scripts contained within, but you'll be missing build-time stuff like the Makefile. You also need to remember to place the unbundled scripts somewhere in /usr/local in order to be able to execute them.

crouton uses the concept of "targets" to decide what to install. While you will have apt-get in your chroot, some targets may need minor hacks to avoid issues when running in the chrooted environment. As such, if you expect to want something that is fulfilled by a target, install that target when you make the chroot and you'll have an easier time. Don't worry if you forget to include a target; you can always update the chroot later and add it. You can see the list of available targets by running crouton -t help.

Once you've set up your chroot, you can easily enter it using the newly-installed enter-chroot command, or one of the target-specific start* commands. Ta-da! That was easy.

Examples

The easy way (assuming you want an Ubuntu LTS with Xfce)

1. Download crouton
2. Open a shell (Ctrl+Alt+T, type shell and hit enter)
3. Copy the installer to an executable location by running sudo install -Dt /usr/local/bin -m 755 ~/Downloads/crouton
4. Now that it's executable, run the installer itself: sudo crouton -t xfce
5. Wait patiently and answer the prompts like a good person.
6. Done! You can jump straight to your Xfce session by running sudo enter-chroot startxfce4 or, as a special shortcut, sudo startxfce4
7. Cycle through Chromium OS and your running graphical chroots using Ctrl+Alt+Shift+Back and Ctrl+Alt+Shift+Forward.
8. Exit the chroot by logging out of Xfce.

With encryption!

1. Add the -e parameter when you run crouton to create an encrypted chroot or encrypt a non-encrypted chroot.
2. You can get some extra protection on your chroot by storing the decryption key separately from the place the chroot is stored. Use the -k parameter to specify a file or directory to store the keys in (such as a USB drive or SD card) when you create the chroot. Beware that if you lose this file, your chroot will not be decryptable. That's kind of the point, of course.

Hey now, Ubuntu 16.04 is pretty old; I'm young and hip

1. The -r parameter specifies which distro release you want to use.
2. Run crouton -r list to list the recognized releases and which distros they belong to.

Wasteful redundancies are wasteful: one clipboard, one browser, one window

1. Install the crouton extension into Chromium OS.
2. Add the extension or xiwi version to your chroot.
3. Try some copy-pasta, or uninstall all your web browsers from the chroot.

Installing the extension and its target gives you synchronized clipboards, the option of using Chromium OS to handle URLs, and allows chroots to create graphical sessions as Chromium OS windows.

I don't always use Linux, but when I do, I use CLI

1. You can save a chunk of space by ditching X and just installing command-line tools using -t core or -t cli-extra
2. Enter the chroot in as many crosh shells as you want simultaneously using sudo enter-chroot
3. Use the Crosh Window extension to keep Chromium OS from eating standard keyboard shortcuts.
4. If you installed cli-extra, startcli will launch a new VT right into the chroot.

A new version of crouton came out; my chroot is therefore obsolete and sad

1. Exit the chroot if you have it open.
2. If you haven't already, download crouton, and copy it so it works: sudo install -Dt /usr/local/bin -m 755 ~/Downloads/crouton
3. Update your chroot with sudo crouton -u -n chrootname. It will update all installed targets.

I want to open my desktop in a window or a tab but I don't have the 'xiwi' target/xmethod.

1. Add 'xiwi' or any other target to an existing chroot with the -u option: sudo crouton -t xiwi -u -n chrootname

This will also make 'xiwi' the default xmethod.

2. If you want to keep the 'xorg' xmethod as the default then pick it first: sudo sh crouton -t xorg,xiwi -u -n chrootname

A backup a day keeps the price-gouging data restoration services away

1. sudo edit-chroot -b chrootname backs up your chroot to a timestamped tarball in the current directory. Chroots are named either via the -n parameter when created or by the release name if -n was not specified.
2. sudo edit-chroot -r chrootname restores the chroot from the most recent timestamped tarball. You can explicitly specify the tarball with -f
3. If your machine is new, powerwashed, or held upside-down and shaken, you can use the crouton installer to restore a chroot and relevant scripts: sudo crouton -f mybackup.tar.gz

Unlike with Chromium OS, the data in your chroot isn't synced to the cloud.

This chroot's name/location/password/existence sucks. How to fix?

1. Check out the edit-chroot command; it likely does what you need it to do.
2. If you set a Chromium OS root password, you can change it with sudo chromeos-setdevpasswd
3. You can change the password inside your chroot with passwd

I want to install the chroot to another location

1. Use -p to specify the directory in which to install the chroot and scripts. Be sure to quote or escape spaces.
2. When entering the chroot for the first time each boot, you will first need to ensure the place you've installed the scripts is in a place that allows executables to run. Determine the mountpoint by running df --output=target /path/to/enter-chroot, then mark the mount exec with sudo mount -o remount,exec /path/to/mountpoint.
3. You can then launch the chroot by specifying the full path of any of the enter-chroot or start* scripts (i.e. sudo /path/to/enter-chroot), or use the -c parameter to explicitly specify the chroots directory.

If for some reason you have to run the installer without touching the local disk, you can (for the time being) run curl -fL https://goo.gl/fd3zc?si=1 | sudo sh -s -- options_for_crouton_installer. Note that this will definitely break in the near future, so don't depend on it.

Downloading bootstrap files over and over again is a waste of time

1. Download crouton
2. Open a shell (Ctrl+Alt+T, type shell and hit enter)
3. Copy the installer to an executable location by running sudo install -Dt /usr/local/bin -m 755 ~/Downloads/crouton
4. Now that it's executable, use the installer to build a bootstrap tarball: sudo crouton -d -f ~/Downloads/mybootstrap.tar.bz2
5. Include the -r parameter if you want to specify for which release to prepare a bootstrap.
6. You can then create chroots using the tarball by running sudo crouton -f ~/Downloads/mybootstrap.tar.bz2. Make sure you also specify the target environment with -t.

This is the quickest way to create multiple chroots at once, since you won't have to determine and download the bootstrap files every time.

Targets are cool. Abusing them for fun and profit is even cooler

1. You can make your own target files (start by copying one of the existing ones) and then use them with any version of crouton via the -T parameter.

This is great for automating common tasks when creating chroots.

Help! I've created a monster that must be slain!

1. The delete-chroot command is your sword, shield, and only true friend. sudo delete-chroot evilchroot
2. It's actually just a shortcut to sudo edit-chroot -d evilchroot, which I suppose makes it a bit of a deceptive Swiss Army knife friend...still good?

Tips

• Chroots are cheap! Create multiple ones using -n, break them, then make new, better ones!
• You can change the distro mirror from the default by using -m
• Want to use a proxy? -P lets you specify one (or disable it).
• A script is installed in your chroot called brightness. You can assign this to keyboard shortcuts to adjust the brightness of the screen (e.g. brightness up) or keyboard (e.g. brightness k down).
• Multiple monitors will work fine in the chroot, but you may have to switch to Chromium OS and back to enable them.
• You can make commands run in the background so that you can close the terminal. This is particularly useful for desktop environments: try running sudo startxfce4 -b
• Want to disable Chromium OS's power management? Run croutonpowerd -i
• Only want power management disabled for the duration of a command? croutonpowerd -i command and arguments will automatically