Skip to content

Generating container recipes & images

EasyBuild has support for generating Singularity and Docker container recipes which will use EasyBuild to build and install a specified software stack. In addition, EasyBuild can (optionally) leverage the build tool provided by the container software of choice to create container images.


The features documented here have been available since EasyBuild v3.6.0 but are still experimental,
which implies they are subject to change in upcoming versions of EasyBuild.

You will need to enable the --experimental configuration option in order to use them.

See Experimental features for more information.

Initially (since EasyBuild v3.6.0), only Singularity ( was supported. Since EasyBuild v3.6.2, generating (recipes for) Docker ( containers is also supported.

In EasyBuild v3.9.2 the support for generating Singularity container recipes/images was enhanced significantly.


  • Docker, or Singularity version 2.4 (or more recent, incl. version 3.x)
  • sudo permissions (only required to actually build container images, see Building container images)


Generating container recipes

(--containerize / -C)

To generate container recipes, use eb --containerize, or eb -C for short.

The resulting container recipe will, in turn, leverage EasyBuild to build and install the software that corresponds to the easyconfig files that are specified as arguments to the eb command (and all required dependencies, if needed).


EasyBuild will refuse to overwrite existing container recipes.

To re-generate an already existing recipe file, use the --force command line option.

Container template recipe


Via the --container-template-recipe configuration option, you can specify a specific container template recipe that EasyBuild should use to generate container recipes.

This gives you control over a variety of aspects, including:

  • the operating system (version) used in the container image
  • the location where EasyBuild installs software within the container
  • how EasyBuild is configured when installing software in the container
  • etc.

When generating container recipes, EasyBuild will replace the following template values:

Container configuration


Using --container-config, values for specific template values can be specified.

Values can be specified as a comma-separated list of <key>=<value> pairs; for example: --container-config bootstrap=localimage,from:example.sif.

Currently supported keywords include:

For more details on the last three, see Linux distro bootstrap agents.


Specifying any unknown keywords will results in an error.

Image-based bootstrap agents

(e.g. docker, library, localimage, shub)

These bootstrap agents involve using an existing container image as a base.

Supported values include:

The from keyword must also be specified when using one of these bootstrap agents.

The localimage bootstrap agents corresponds to using a local container image file as a base, where it's path is specified using the from keyword. For example: "bootstrap=localimage,from=/home/example/base.sif".

Each of the other image-based bootstrap agents imply that the container image to use as a base is downloaded from the corresponding registry, ad specified through the from keyword, with a specific format:

  • for docker bootstrap agent: <registry>/<namespace>/<container>:<tag>@<digest>
  • for library bootstrap agent: <entity>/<collection>/<container>:<tag>
  • for shub bootstrap agent: <registry>/<username>/<container-name>:<tag>@digest

For more details, see

Requirements for base container image

There are a couple of specific requirements for the base container image:

  • all dependencies of EasyBuild must be installed, including:
    • Python 2.7 or 3.6+
    • Lmod
    • standard tools & utilities like make, patch, tar, etc.
    • OS packages for system libraries like OpenSSL

See also Requirements

Each generated container recipe will include commands to create the easybuild user if it doesn't exist yet, as well as commands to create the /app and /scratch directories and give the easybuild user write permissions to those locations.


The generated container recipe currently hardcodes some of this.
We intend to make this more configurable in a future version of EasyBuild.

Linux distro bootstrap agents

(e.g. arch, busybox, debootstrap, yum, zypper)

Dedicated bootstrap agents are supported for different flavors of Linux distributions, including:

  • arch: Arch Linux
  • busybox: BusyBox Linux
  • debootstrap: apt-based systems like Ubuntu/Debian
  • yum: yum-based systems like CentOS
  • zypper: zypper-based systems like openSUSE

When one of these bootstrap agents is used, additional keywords can be specified:

include keyword: OS packages to include

Via the include keywords, a list of packages can be specified that should be include on top of the base OS installation.

For some bootstrap agents, a default value is used if no value is specified:

  • for the yum bootstrap agent: yum
  • for the zypper bootstrap agent: zypper

See also and

mirrorurl keyword: mirror URL to use to download OS

For most of the Linux distro bootstrap agents (all except arch), Singularity requires that a mirror URL is specified that will be used when downloading the corresponding OS.

You can specify a value using the mirrorurl keyword. For example: "bootstrap=yum,mirrorurl=".

EasyBuild will use a default value for mirrorurl if no other value is specified:

  • busybox:{OSVERSION}/busybox-x86_64
  • debootstrap:
  • yum:{OSVERSION}/%{OSVERSION}/os/x86_64/
  • zypper::{OSVERSION}/repo/oss/
osversion keyword: OS version to use

Using the osversion keyword you can specify which OS version should be installed.

Note that is this only required/used if value for the mirrorurl value contains %{OSVERSION}s.

For example: "bootstrap=yum,osversion=7".

Building container images


To instruct EasyBuild to also build a container image from the generated container recipe, use --container-build-image (in combination with -C or --containerize).

EasyBuild will leverage functionality provided by the container software of choice (see Type of container recipe/image to generate) to build the container image.

For example, in the case of Singularity, EasyBuild will run sudo /path/to/singularity build on the generated container recipe.


In order to leverage the image building functionality of the container software, admin privileges are
typically required. Therefore, EasyBuild will run the command to build the container image with sudo. You may need to enter your password to let the command execute.

EasyBuild will only run the actual container image build command with sudo. It will not use elevated privileges for anything else.

In case of doubt, you can use --extended-dry-run or -x do perform a dry run, so you can evaluate which commands will be executed (see also Extended dry run.

If you're not comfortable with this, you can just let EasyBuild generate the container recipe, and then use that to build the actual container images yourself, either locally or through Singularity Hub (

The container image will be placed in the location specified by the --containerpath configuration option (see Location for generated container recipes & images), next to the generated container recipe that was used to build the image.


When building container images, make sure to use a file system location with sufficient available storage space. Singularity may pull metadata during the build, and each image can range from several hundred MBs to GBs, depending on software stack you are including in the container image.


EasyBuild will refuse to overwrite existing container images.

To re-generate an already existing image file, use the --force command line option.

Example usage

In this example, we will use a pre-built base container image located at example.sif (see also Image-based bootstrap agents).

To let EasyBuild generate a container recipe for GCC 6.4.0 + binutils 2.28:

eb GCC-6.4.0-2.28.eb --containerize --container-config bootstrap=localimage,from=example.sif --experimental

With other configuration options left to default (see output of eb --show-config), this will result in a Singularity container recipe using example.sif as base image, which will be stored in $HOME/.local/easybuild/containers:

$ eb GCC-6.4.0-2.28.eb --containerize --container-config bootstrap=localimage,from=example.sif --experimental
== temporary log file in case of crash /tmp/eb-dLZTNF/easybuild-LPLeG0.log
== Singularity definition file created at /home/example/.local/easybuild/containers/Singularity.GCC-6.4.0-2.28
== Temporary log file(s) /tmp/eb-dLZTNF/easybuild-LPLeG0.log* have been removed.
== Temporary directory /tmp/eb-dLZTNF has been removed.

Docker supports a limited set of the container options. Example of commands that can be used to generate Docker containers are:

eb  --containerize --container-type=docker --experimental --container-config=ubuntu:20.04 zlib-1.2.11.eb
eb  --containerize --container-type=docker --experimental --container-config=centos:7 zlib-1.2.11.eb

Example of a generated container recipe

Below is an example of container recipe for that was generated by EasyBuild, using the following command:

eb Python-3.6.4-foss-2018a.eb -C --container-config bootstrap=yum,osversion=7 --experimental
Bootstrap: yum
OSVersion: 7
Include: yum

yum install --quiet --assumeyes epel-release
yum install --quiet --assumeyes python setuptools Lmod
yum install --quiet --assumeyes python-pip
yum install --quiet --assumeyes bzip2 gzip tar zip unzip xz
yum install --quiet --assumeyes curl wget
yum install --quiet --assumeyes patch make
yum install --quiet --assumeyes file git which
yum install --quiet --assumeyes gcc-c++
yum install --quiet --assumeyes perl-Data-Dumper
yum install --quiet --assumeyes perl-Thread-Queue
yum --skip-broken --quiet --assumeyes install libibverbs-dev libibverbs-devel rdma-core-devel
yum --skip-broken --quiet --assumeyes install openssl-devel libssl-dev libopenssl-devel

# install EasyBuild using pip
pip install -U setuptools
pip install 'vsc-install<0.11.4' 'vsc-base<2.9.0'
pip install easybuild

# create 'easybuild' user (if missing)
id easybuild || useradd easybuild

# create /app software installation prefix + /scratch sandbox directory
if [ ! -d /app ]; then mkdir -p /app; chown easybuild:easybuild -R /app; fi
if [ ! -d /scratch ]; then mkdir -p /scratch; chown easybuild:easybuild -R /scratch; fi

# install Lmod RC file
cat > /etc/lmodrc.lua << EOF
scDescriptT = {
    ["dir"]       = "/app/lmodcache",
    ["timestamp"] = "/app/lmodcache/timestamp",

# change to 'easybuild' user
su - easybuild

# verbose commands, exit on first error
set -ve

# configure EasyBuild

# use /scratch as general prefix, used for sources, build directories, etc.
export EASYBUILD_PREFIX=/scratch

# also use /scratch for temporary directories
export EASYBUILD_TMPDIR=/scratch/tmp

# download sources to /scratch/sources, but also consider files located in /tmp/easybuild/sources;
# that way, source files that can not be downloaded can be seeded in
export EASYBUILD_SOURCEPATH=/scratch/sources:/tmp/easybuild/sources

# install software & modules into /app

# use EasyBuild to install specified software
eb Python-3.6.4-foss-2018a.eb --robot

# update Lmod cache
mkdir -p /app/lmodcache
$LMOD_DIR/update_lmod_system_cache_files -d /app/lmodcache -t /app/lmodcache/timestamp /app/modules/all

# exit from 'easybuild' user

# cleanup, everything in /scratch is assumed to be temporary
rm -rf /scratch/*

eval "$@"

# make sure that 'module' and 'ml' commands are defined
source /etc/profile
# increase threshold time for Lmod to write cache in $HOME (which we don't want to do)
export LMOD_SHORT_TIME=86400
# purge any modules that may be loaded outside container
module --force purge
# avoid picking up modules from outside of container
module unuse $MODULEPATH
# pick up modules installed in /app
module use /app/modules/all
# load module(s) corresponding to installed software
module load Python/3.6.4-foss-2018a


The generated container recipe includes a bunch of yum install commands to install additional required/useful OS packages, pip install commands to install EasyBuild (if it's not installed yet), commands to create the easybuild user and provide write access to the /app and /scratch directories, and to configure Lmod and update the Lmod cache after software was installed with EasyBuild.

In addition, the generated module files will follow the default module naming scheme (EasyBuildMNS). The modules that correspond to the easyconfig files that were specified on the command line will be loaded automatically, see the statements in the %environment section of the generated container recipe.

Example of building container image

You can instruct EasyBuild to also build the container image by also using --container-build-image.

Note that you will need to enter your sudo password (unless you recently executed a sudo command in the same shell session):

$ eb GCC-6.4.0-2.28.eb --containerize --container-config bootstrap=localimage,from=/tmp/example.sif --container-build-image --experimental
== temporary log file in case of crash /tmp/eb-aYXYC8/easybuild-8uXhvu.log
== Singularity tool found at /usr/bin/singularity
== Singularity version '2.4.6' is 2.4 or higher ... OK
== Singularity definition file created at /home/example/.local/easybuild/containers/Singularity.GCC-6.4.0-2.28
== Running 'sudo /usr/bin/singularity build  /home/example/.local/easybuild/containers/GCC-6.4.0-2.28.sif /home/example/.local/easybuild/containers/Singularity.GCC-6.4.0-2.28', you may need to enter your 'sudo' password...
== (streaming) output for command 'sudo /usr/bin/singularity build  /home/example/.local/easybuild/containers/GCC-6.4.0-2.28.sif /home/example/.local/easybuild/containers/Singularity.GCC-6.4.0-2.28':
Using container recipe deffile: /home/example/.local/easybuild/containers/Singularity.GCC-6.4.0-2.28
Sanitizing environment
Adding base Singularity environment to container
== temporary log file in case of crash /scratch/tmp/eb-WnmCI_/easybuild-GcKyY9.log
== resolving dependencies ...
== building and installing GCCcore/6.4.0...
== building and installing binutils/2.28-GCCcore-6.4.0...
== building and installing GCC/6.4.0-2.28...
== COMPLETED: Installation ended successfully
== Results of the build can be found in the log file(s) /app/software/GCC/6.4.0-2.28/easybuild/easybuild-GCC-6.4.0-20180424.084946.log
== Build succeeded for 15 out of 15
Building Singularity image...
Singularity container built: /home/example/.local/easybuild/containers/GCC-6.4.0-2.28.sif
Cleaning up...
== Singularity image created at /home/example/.local/easybuild/containers/GCC-6.4.0-2.28.sif
== Temporary log file(s) /tmp/eb-aYXYC8/easybuild-8uXhvu.log* have been removed.
== Temporary directory /tmp/eb-aYXYC8 has been removed.

The inspect the container image, you can use singularity shell to start a shell session in the container:

$ singularity shell --shell "/bin/bash --norc" $HOME/.local/easybuild/containers/GCC-6.4.0-2.28.sif

Singularity GCC-6.4.0-2.28.sif:~> module list

Currently Loaded Modules:
  1) GCCcore/6.4.0   2) binutils/2.28-GCCcore-6.4.0   3) GCC/6.4.0-2.28

Singularity GCC-6.4.0-2.28.sif:~> which gcc

Singularity GCC-6.4.0-2.28.sif:~> gcc --version
gcc (GCC) 6.4.0


We are passing --shell "/bin/bash --norc to singularity shell to avoid that the .bashrc login
script that may be present in your home directory is sourced, since that may include statements that are not relevant in the container environment.

Or, you can use singularity exec to execute a command in the container.

Compare the output of running which gcc and gcc --version locally:

$ which gcc
$ gcc --version
gcc (GCC) 4.8.5 20150623 (Red Hat 4.8.5-16)

and the output when running the same commands in the container:

$ singularity exec GCC-6.4.0-2.28.sif which gcc

$ singularity exec GCC-6.4.0-2.28.sif gcc --version
gcc (GCC) 6.4.0



You can specify each of these configuration options either as options to the eb command,
via the equivalent $EASYBUILD_CONTAINER* environment variable, or via an EasyBuild configuration file; see Supported configuration types.

Location for generated container recipes & images


To control the location where EasyBuild will put generated container recipes & images, use the --containerpath configuration setting. Next to providing this as an option to the eb command, you can also define the $EASYBUILD_CONTAINERPATH environment variable or specify containerpath in an EasyBuild configuration file.

The default value for this location is $HOME/.local/easybuild/containers, unless the --prefix configuration setting was provided, in which case it becomes <prefix>/containers (see Overall prefix path).

Use eb --show-full-config | grep containerpath to determine the currently active setting.

Container image format



This is only relevant when creating Singularity container images;
the value for --container-image-format is ignored when creating Docker container images.

The format for container images that EasyBuild is produces via the functionality provided by the container software can be controlled via the --container-image-format configuration setting.

For Singularity containers (see Type of container recipe/image to generate), three image formats are supported:

  • squashfs (default when using Singularity 2.x): compressed images using squashfs read-only file system
  • sif (default when using Singularity 3.x): compressed read-only Singularity Image File (SIF)
  • ext3: writable image file using ext3 file system (only supported with Singularity 2.x)
  • sandbox: container image in a regular directory

See also .

Name for container recipe & image


By default, EasyBuild will use the name of the first easyconfig file (without the .eb suffix) as a name for both the container recipe and image.

You can specify an altername name using the --container-image-name configuration setting.

The filename of generated container recipe will be Singularity.<name>.

The filename of the container image will be <name><extension>, where the value for <extension> depends on the image format (see Container image format):

  • '.simg' for squashfs Singularity container images (only with Singularity 2.x)
  • '.img' for ext3 Singularity container images (only with Singularity 2.x)
  • '.sif' for Singularity container images in Singularity Image Format (SIF) (only with Singularity 3.x)
  • empty for sandbox Singularity container images (in which case the container image is actually a directory rather than a file)
  • empty for Docker container images

Temporary directory for creating container images


The container software that EasyBuild leverages to build container images may be using a temporary directory in a location that doesn't have sufficient free space.

You can instruct EasyBuild to pass an alternate location via the --container-tmpdir configuration setting.

For Singularity, the default is to use /tmp, see If --container-tmpdir is specified, the $SINGULARITY_TMPDIR environment variable will be defined accordingly to let Singularity use that location instead.

Type of container recipe/image to generate


With the --container-type configuration option, you can specify what type of container recipe/image EasyBuild should generated. Possible values are:

'Stacking' container images

To avoid long build times and excessive large container images, you can construct your target container image step-by-step, by first building a base container image for the compiler toolchain you want to use, and then using it to build a container images for a particular (set of) software package(s).

For example, to build a container image for Python 3.6.4 built with the foss/2018a toolchain:

$ cd /tmp

# use current directory as location for generated container recipes & images

# build base container image for OpenMPI + GCC parts of foss/2018a toolchain, on top of CentOS 7.4 base image
$ eb -C --container-build-image OpenMPI-2.1.2-GCC-6.4.0-2.28.eb --container-config bootstrap=yum,osversion=7 --experimental
== Singularity image created at /tmp/OpenMPI-2.1.2-GCC-6.4.0-2.28.sif

$ ls -lh OpenMPI-2.1.2-GCC-6.4.0-2.28.sif
-rwxr-xr-x 1 root root 590M Apr 24 11:43 OpenMPI-2.1.2-GCC-6.4.0-2.28.sif

# build another container image for the for the full foss/2018a toolchain, using the OpenMPI + GCC container as a base
$ eb -C --container-build-image foss-2018a.eb --container-config bootstrap=localimage,from=OpenMPI-2.1.2-GCC-6.4.0-2.28.sif --experimental
== Singularity image created at /tmp/foss-2018a.sif

$ ls -lh foss-2018a.sif
-rwxr-xr-x 1 root root 614M Apr 24 13:11 foss-2018a.sif

# build container image for Python 3.6.4 with foss/2018a toolchain by leveraging base container image foss-2018a.sif
$ eb -C --container-build-image Python-3.6.4-foss-2018a.eb --container-config bootstrap=localimage,from=foss-2018a.sif --experimental
== Singularity image created at /tmp/Python-3.6.4-foss-2018a.sif

$ ls -lh Python-3.6.4-foss-2018a.sif
-rwxr-xr-x 1 root root 759M Apr 24 14:01 Python-3.6.4-foss-2018a.sif

$ singularity exec Python-3.6.4-foss-2018a.sif which python

$ singularity exec Python-3.6.4-foss-2018a.sif python -V
vsc40023 belongs to gsingularity
Python 3.6.4

Seeding in source files for container build process

In some cases, you may need to "seed in" manually downloaded source files into the container build environment, because the sources can not be downloaded automatically.

As shown in Example of a generated container recipe, the container recipe generated by EasyBuild includes /tmp/easybuild/sources/ as a fallback directory in the list of locations considered by EasyBuild when looking for sources/patches (see also Source path).

That way, you can copy source files that should be available when building the container image into /tmp/easybuild/sources/.