7.1 Invoking guix shell

The purpose of guix shell is to make it easy to create one-off software environments, without changing one’s profile. It is typically used to create development environments; it is also a convenient way to run applications without “polluting” your profile.

Note: The guix shell command was recently introduced to supersede guix environment (see Invoking guix environment). If you are familiar with guix environment, you will notice that it is similar but also—we hope!—more convenient.

The general syntax is:

guix shell [options] [package…]

The following example creates an environment containing Python and NumPy, building or downloading any missing package, and runs the python3 command in that environment:

guix shell python python-numpy -- python3

Development environments can be created as in the example below, which spawns an interactive shell containing all the dependencies and environment variables needed to work on Inkscape:

guix shell --development inkscape

Exiting the shell places the user back in the original environment before guix shell was invoked. The next garbage collection (see Invoking guix gc) may clean up packages that were installed in the environment and that are no longer used outside of it.

As an added convenience, when running from a directory that contains a manifest.scm or a guix.scm file (in this order), possibly in a parent directory, guix shell automatically loads the file—provided the directory is listed in ~/.config/guix/shell-authorized-directories, and only for interactive use:

guix shell

This provides an easy way to define, share, and enter development environments.

By default, the shell session or command runs in an augmented environment, where the new packages are added to search path environment variables such as PATH. You can, instead, choose to create an isolated environment containing nothing but the packages you asked for. Passing the --pure option clears environment variable definitions found in the parent environment¹¹; passing --container goes one step further by spawning a container isolated from the rest of the system:

guix shell --container emacs gcc-toolchain

The command above spawns an interactive shell in a container where nothing but emacs, gcc-toolchain, and their dependencies is available. The container lacks network access and shares no files other than the current working directory with the surrounding environment. This is useful to prevent access to system-wide resources such as /usr/bin on foreign distros.

This --container option can also prove useful if you wish to run a security-sensitive application, such as a web browser, in an isolated environment. For example, the command below launches Ungoogled-Chromium in an isolated environment, this time sharing network access with the host and preserving its DISPLAY environment variable, but without even sharing the current directory:

guix shell --container --network --no-cwd ungoogled-chromium \
  --preserve='^DISPLAY$' -- chromium

guix shell defines the GUIX_ENVIRONMENT variable in the shell it spawns; its value is the file name of the profile of this environment. This allows users to, say, define a specific prompt for development environments in their .bashrc (see Bash Startup Files in The GNU Bash Reference Manual):

if [ -n "$GUIX_ENVIRONMENT" ]
then
    export PS1="\u@\h \w [dev]\$ "
fi

... or to browse the profile:

$ ls "$GUIX_ENVIRONMENT/bin"

The available options are summarized below.

--check

Set up the environment and check whether the shell would clobber environment variables. It’s a good idea to use this option the first time you run guix shell for an interactive session to make sure your setup is correct.

For example, if the shell modifies the PATH environment variable, report it since you would get a different environment than what you asked for.

Such problems usually indicate that the shell startup files are unexpectedly modifying those environment variables. For example, if you are using Bash, make sure that environment variables are set or modified in ~/.bash_profile and not in ~/.bashrc—the former is sourced only by log-in shells. See Bash Startup Files in The GNU Bash Reference Manual, for details on Bash start-up files.

--development

-D

Cause guix shell to include in the environment the dependencies of the following package rather than the package itself. This can be combined with other packages. For instance, the command below starts an interactive shell containing the build-time dependencies of GNU Guile, plus Autoconf, Automake, and Libtool:

guix shell -D guile autoconf automake libtool

--expression=expr

-e expr

Create an environment for the package or list of packages that expr evaluates to.

For example, running:

guix shell -D -e '(@ (gnu packages maths) petsc-openmpi)'

starts a shell with the environment for this specific variant of the PETSc package.

Running:

guix shell -e '(@ (gnu) %base-packages)'

starts a shell with all the base system packages available.

The above commands only use the default output of the given packages. To select other outputs, two element tuples can be specified:

guix shell -e '(list (@ (gnu packages bash) bash) "include")'

--file=file

-f file

Create an environment containing the package or list of packages that the code within file evaluates to.

As an example, file might contain a definition like this (see Defining Packages):

(use-modules (guix)
             (gnu packages gdb)
             (gnu packages autotools)
             (gnu packages texinfo))

;; Augment the package definition of GDB with the build tools
;; needed when developing GDB (and which are not needed when
;; simply installing it.)
(package (inherit gdb)
  (native-inputs `(("autoconf" ,autoconf-2.64)
                   ("automake" ,automake)
                   ("texinfo" ,texinfo)
                   ,@(package-native-inputs gdb))))

With the file above, you can enter a development environment for GDB by running:

guix shell -D -f gdb-devel.scm

--manifest=file

-m file

Create an environment for the packages contained in the manifest object returned by the Scheme code in file. This option can be repeated several times, in which case the manifests are concatenated.

This is similar to the same-named option in guix package (see --manifest) and uses the same manifest files.

--rebuild-cache

When using --manifest, --file, or when invoked without arguments, guix shell caches the environment so that subsequent uses are instantaneous. The cache is invalidated anytime the file is modified.

The --rebuild-cache forces the cached environment to be refreshed even if the file has not changed. This is useful if the guix.scm or manifest.scm has external dependencies, or if its behavior depends, say, on environment variables.

--pure

Unset existing environment variables when building the new environment, except those specified with --preserve (see below). This has the effect of creating an environment in which search paths only contain package inputs.

--preserve=regexp

-E regexp

When used alongside --pure, preserve the environment variables matching regexp—in other words, put them on a “white list” of environment variables that must be preserved. This option can be repeated several times.

guix shell --pure --preserve=^SLURM openmpi … \
  -- mpirun …

This example runs mpirun in a context where the only environment variables defined are PATH, environment variables whose name starts with ‘SLURM’, as well as the usual “precious” variables (HOME, USER, etc.).

--search-paths

Display the environment variable definitions that make up the environment.

--system=system

-s system

Attempt to build for system—e.g., i686-linux.

--container

-C

Run command within an isolated container. The current working directory outside the container is mapped inside the container. Additionally, unless overridden with --user, a dummy home directory is created that matches the current user’s home directory, and /etc/passwd is configured accordingly.

The spawned process runs as the current user outside the container. Inside the container, it has the same UID and GID as the current user, unless --user is passed (see below).

--network

-N

For containers, share the network namespace with the host system. Containers created without this flag only have access to the loopback device.

--link-profile

-P

For containers, link the environment profile to ~/.guix-profile within the container and set GUIX_ENVIRONMENT to that. This is equivalent to making ~/.guix-profile a symlink to the actual profile within the container. Linking will fail and abort the environment if the directory already exists, which will certainly be the case if guix shell was invoked in the user’s home directory.

Certain packages are configured to look in ~/.guix-profile for configuration files and data;¹² --link-profile allows these programs to behave as expected within the environment.

--user=user

-u user

For containers, use the username user in place of the current user. The generated /etc/passwd entry within the container will contain the name user, the home directory will be /home/user, and no user GECOS data will be copied. Furthermore, the UID and GID inside the container are 1000. user need not exist on the system.

Additionally, any shared or exposed path (see --share and --expose respectively) whose target is within the current user’s home directory will be remapped relative to /home/USER; this includes the automatic mapping of the current working directory.

# will expose paths as /home/foo/wd, /home/foo/test, and /home/foo/target
cd $HOME/wd
guix shell --container --user=foo \
     --expose=$HOME/test \
     --expose=/tmp/target=$HOME/target

While this will limit the leaking of user identity through home paths and each of the user fields, this is only one useful component of a broader privacy/anonymity solution—not one in and of itself.

--no-cwd

For containers, the default behavior is to share the current working directory with the isolated container and immediately change to that directory within the container. If this is undesirable, --no-cwd will cause the current working directory to not be automatically shared and will change to the user’s home directory within the container instead. See also --user.

--expose=source[=target]

--share=source[=target]

For containers, --expose (resp. --share) exposes the file system source from the host system as the read-only (resp. writable) file system target within the container. If target is not specified, source is used as the target mount point in the container.

The example below spawns a Guile REPL in a container in which the user’s home directory is accessible read-only via the /exchange directory:

guix shell --container --expose=$HOME=/exchange guile -- guile

--root=file

-r file

Make file a symlink to the profile for this environment, and register it as a garbage collector root.

This is useful if you want to protect your environment from garbage collection, to make it “persistent”.

When this option is omitted, the environment is protected from garbage collection only for the duration of the guix shell session. This means that next time you recreate the same environment, you could have to rebuild or re-download packages. See Invoking guix gc, for more on GC roots.

guix shell also supports all of the common build options that guix build supports (see Common Build Options) as well as package transformation options (see Package Transformation Options).