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The default environment

In the typical development case you would create a directory for your project. flox init to create an environment for it, then flox activate in that directory when you want to work on that project. The packages in that environment are available when the environment is active, and they're unavailable otherwise. But what about packages that you always want available?

Without Flox, you may turn to your system's package manager (apt, yum, brew, etc) in order to install packages system-wide. This has a number of drawbacks:

  • You often only have a single package version to choose from.
  • You often can't install multiple versions side-by-side.
  • You can't ensure that multiple machines get the exact same version.
  • You may not be able to back up the list of installed packages.

The Flox default environment doesn't have these problems, so let's take a look at how to set it up.

Initial setup

At the most basic level, the default environment is simply an environment called default. default environments are typically shared via FloxHub; We refer to the one associated with your account, as your default environment.

In some cases Flox will prompt to set up your default environment for you. To create the default environment yourself, make sure you are logged in to FloxHub, and initialize a FloxHub environment under your account:

flox auth status || flox auth login
✅ Authentication complete
✅ Logged in as <youruser>

flox init -r <youruser>/default

Once the environment has been created, you'll want to configure your shell to activate the environment with every new shell. This can be done as part of the automatic setup, or you can add a single line to your shell's RC file:

Depending on the context, Bash will load different startup files. For that reason, we need to add a line to two different files: .bashrc and .profile. Add the following line to the very end of each of those files:

eval "$(flox activate -r <your username>/default -m run)"

Add the following line to the very end of your .zprofile and .zshrc files:

eval "$(flox activate -r <your username>/default -m run)"

Add the following line to the very end of your config.fish file:

flox activate -r <your username>/default -m run | source

Add the following line to the very end of your .tcshrc file:

** For FloxHub environments:**

eval "`flox activate -r <your username>/default -m run`"

Once you've added that line to your shell, you'll need to restart your shell (or open a new one) for the changes to take effect. If you don't want to activate it automatically, the default environment can simply be activated using -d parameter of the Flox CLI like so:

flox activate -r <your username>/default

Taking it for a spin

Now let's test out your new default environment. If you're in an arbitrary directory and apt install hello you would expect it to be available no matter what directory you're in. Let's do the same with Flox.

Let's create a new temporary directory that we know doesn't have an environment in it.

cd $(mktemp -d)

Now we'll install a package and see that it gets installed to the default environment, like you would expect from your system's package manager:

$ flox install hello
✅ 'hello' installed to environment 'default'

It worked (though you shouldn't be surprised; Flox is awesome)!

Installing packages to the default environment from another Flox environment

If you're in a project directory with an existing Flox environment, unsurprisingly, running flox install <pkg> will install the package to the environment in that directory, rather than your default environment.

Nevertheless, it's still easy to install whatever you wish to your default environment. All you need to do is pass the -d argument to the install command, like so:

flox install -r <your username>/default ~ hello

When you do this, you should see the following output, indicating success:

✅ 'hello' installed to environment 'default'

Customization

Depending on when you created your default environment (the default was changed recently), you may also see flox [default] as part of your prompt for every new shell. You can configure that with a single command:

flox config --set hide_default_prompt false

flox config --set hide_default_prompt true

Sharing

Since the default environment is "just" another FloxHub environment, it's possible to push this environment and share it between machines.

In fact, activating or initializing default environments on other machines will link to the environment that is already on FloxHub. To use the environment on other machines simply log in and add the activation to your dotfiles as described above.

Changes made to the environment locally (e.g. newly installed packages) can be synchronized with flox push and pull.

Generations

Pushing an environment creates the first version of the environment tracked on FloxHub, which is called a generation.

To see how generations can be used to undo changes, edit the environment, perhaps adding a variable FOO = "bar" to the [vars] section. Then push the environment to FloxHub:

flox edit;
flox push

This should print a link to your environment on FloxHub. Follow the link and click the Generations tab. This should show the most recent generation created by the flox edit command.

To revert to the version of the environment prior to the edit, run rollback:

flox generations rollback;
flox push

Now if you run flox pull on another host, you'll get the rolled-back environment, without the edit.

Conclusion

Whether you want a reproducible package manager for your whole system, or you want reproducible, cross-platform developer environments, Flox has you covered. Even better, if you want both a package manager and developer environments, with Flox you only need to learn one tool.

Detached and directory based default environments

Since default environments are normal Flox environments, you can use any other environment the same way.

For example you can

flox init -d ~

flox pull --copy -d ~ owner/name

flox pull -d ~ owner/name

If you choose to automatically activate the environment in your rc files, change the flox activate -r <youruser> accordingly to e.g. flox activate -d ~.