Micromamba

micromamba is a small, pure-C++ executable with enough functionalities to bootstrap fully functional conda-environments.

Still at early stage, it’s main usage is in continous integration pipelines: since it’s a single executable, it reduces dramatically bandwidth usage and provide fast operations.

Quickstarts

micromamba supports a subset of all mamba or conda commands and implements a command line interface from scratch.
You can see all implemented commands with micromamba --help:
$ micromamba --help

Subcommands:
  activate                    Activate a conda / micromamba environment
  deactivate                  Deactivate a conda / micromamba environment
  shell                       Generate shell init scripts
  create                      Create new environment
  install                     Install packages in active environment
  update                      Update packages in active environment
  remove                      Remove packages from active environment
  list                        List packages in active environment
  config                      Configuration of micromamba
  info                        Information about micromamba
  clean                       Clean package cache
  constructor                 Commands to support using micromamba in constructor
  env                         List environments

To activate an environment just call micromamba activate /path/to/env or, when it’s a named environment in your root prefix, then you can also use micromamba activate myenv.

micromamba expects to find the root prefix set by $MAMBA_ROOT_PREFIX environment variable. You can also provide it using CLI option -r,--root-prefix.

Named environments then live in $MAMBA_ROOT_PREFIX/envs/.

For more details, please read about configuration.

After activation, you can run install to add new packages to the environment.

$ micromamba install xtensor -c conda-forge

Using create, you can also create environments:

$ micromamba create -n xtensor_env xtensor xsimd -c conda-forge
                                           __
          __  ______ ___  ____ _____ ___  / /_  ____ _
         / / / / __ `__ \/ __ `/ __ `__ \/ __ \/ __ `/
        / /_/ / / / / / / /_/ / / / / / / /_/ / /_/ /
       / .___/_/ /_/ /_/\__,_/_/ /_/ /_/_.___/\__,_/
      /_/

conda-forge/noarch       [====================] (00m:01s) Done
conda-forge/linux-64     [====================] (00m:04s) Done

Transaction

  Prefix: /home/wolfv/miniconda3/envs/xtensor_env

  Updating specs:

  - xtensor
  - xsimd


  Package        Version  Build        Channel                    Size
────────────────────────────────────────────────────────────────────────
  Install:
────────────────────────────────────────────────────────────────────────

  _libgcc_mutex      0.1  conda_forge  conda-forge/linux-64     Cached
  _openmp_mutex      4.5  1_gnu        conda-forge/linux-64     Cached
  libgcc-ng        9.3.0  h5dbcf3e_17  conda-forge/linux-64     Cached
  libgomp          9.3.0  h5dbcf3e_17  conda-forge/linux-64     Cached
  libstdcxx-ng     9.3.0  h2ae2ef3_17  conda-forge/linux-64     Cached
  xsimd            7.4.9  hc9558a2_0   conda-forge/linux-64     102 KB
  xtensor         0.21.9  h0efe328_0   conda-forge/linux-64     183 KB
  xtl             0.6.21  h0efe328_0   conda-forge/linux-64     Cached

  Summary:

  Install: 8 packages

  Total download: 285 KB

────────────────────────────────────────────────────────────────────────

Confirm changes: [Y/n] ...

After the installation is finished, the environment can be activated with:

$ micromamba activate xtensor_env

Specification files

The create syntax also allows you to use specification or environment files (also called spec files) to easily re-create environments.

The three supported syntaxes are: yaml, txt and explicit spec files.

Simple text spec files

The txt file contains one spec per line. For example, this could look like:

xtensor
numpy 1.19
xsimd >=7.4

To use this file, pass:

$ micromamba create -n from_file -f spec_file.txt -c conda-forge

Note

You can pass multiple text spec files by repeating the -f,--file argument.

YAML spec files

More powerful are YAML files like the following, because they already contain a desired environment name and the channels to use:

name: testenv
channels:
  - conda-forge
dependencies:
  - python >=3.6,<3.7
  - ipykernel >=5.1
  - ipywidgets

They are used the same way as text files:

$ micromamba create -f env.yml

Note

CLI options will keep precedence over target prefix or channels specified in spec files.

Warning

YAML spec files do not allow multiple files.

Explicit spec files

Using conda you can generate explicit environment lock files. For this, create an environment and execute:

$ conda list --explicit --md5

These environment files look like the following and precisely “pin” the desired package + version + build string:

# This file may be used to create an environment using:
# $ conda create --name <env> --file <this file>
# platform: linux-64
@EXPLICIT
https://conda.anaconda.org/conda-forge/linux-64/_libgcc_mutex-0.1-conda_forge.tar.bz2#d7c89558ba9fa0495403155b64376d81
https://conda.anaconda.org/conda-forge/linux-64/libstdcxx-ng-9.3.0-h2ae2ef3_17.tar.bz2#342f3c931d0a3a209ab09a522469d20c
https://conda.anaconda.org/conda-forge/linux-64/libgomp-9.3.0-h5dbcf3e_17.tar.bz2#8fd587013b9da8b52050268d50c12305
https://conda.anaconda.org/conda-forge/linux-64/_openmp_mutex-4.5-1_gnu.tar.bz2#561e277319a41d4f24f5c05a9ef63c04
https://conda.anaconda.org/conda-forge/linux-64/libgcc-ng-9.3.0-h5dbcf3e_17.tar.bz2#fc9f5adabc4d55cd4b491332adc413e0
https://conda.anaconda.org/conda-forge/linux-64/xtl-0.6.21-h0efe328_0.tar.bz2#9eee90b98fd394db7a049792e67e1659
https://conda.anaconda.org/conda-forge/linux-64/xtensor-0.21.8-hc9558a2_0.tar.bz2#1030174db5c183f3afb4181a0a02873d

To install such a file with micromamba, just pass the -f flag again:

$ micromamba create -n xtensor -c conda-forge -f explicit_env.txt