diff --git a/docker/Dockerfile b/docker/Dockerfile
--- a/docker/Dockerfile
+++ b/docker/Dockerfile
@@ -1,4 +1,4 @@
-FROM python:3.7
+FROM python:3.9
 
 ARG PGDG_REPO=http://apt.postgresql.org/pub/repos/apt
 ARG PGDG_GPG_KEY=https://www.postgresql.org/media/keys/ACCC4CF8.asc
@@ -23,12 +23,15 @@
   > /etc/apt/sources.list.d/yarnpkg.list && \
   curl -fsSL ${YARN_GPG_KEY} | gpg --dearmor > ${YARN_KEYRING}
 
+# RUN curl -L https://nixos.org/nix/install | sh
+
 # warning: the py:3.7 image comes with python3.9 installed from debian; do not
 # add debian python packages here, they would not be usable for the py37 based
 # environment used in this image.
 RUN export DEBIAN_FRONTEND=noninteractive && \
   apt-get update && apt-get upgrade -y && \
   apt-get install -y \
+  nix-bin \
   libapr1-dev \
   libaprutil1-dev \
   libcmph-dev \
diff --git a/docker/conf/lister.yml b/docker/conf/lister.yml
--- a/docker/conf/lister.yml
+++ b/docker/conf/lister.yml
@@ -48,3 +48,4 @@
     - swh.lister.rubygems.tasks.RubyGemsListerTask
     - swh.lister.sourceforge.tasks.FullSourceForgeLister
     - swh.lister.sourceforge.tasks.IncrementalSourceForgeLister
+    - swh.lister.nixguix.tasks.NixGuixListerTask
diff --git a/docker/conf/loader.yml b/docker/conf/loader.yml
--- a/docker/conf/loader.yml
+++ b/docker/conf/loader.yml
@@ -15,39 +15,40 @@
   broker_heartbeat: null
   task_broker: amqp://guest:guest@amqp//
   task_queues:
-    - swh.loader.bzr.tasks.LoadBazaar
-    - swh.loader.cvs.tasks.LoadCvsRepository
-    - swh.loader.dir.tasks.LoadDirRepository
-    - swh.loader.git.tasks.LoadDiskGitRepository
-    - swh.loader.git.tasks.UncompressAndLoadDiskGitRepository
-    - swh.loader.git.tasks.UpdateGitRepository
-    - swh.loader.mercurial.tasks.LoadArchiveMercurial
-    - swh.loader.mercurial.tasks.LoadMercurial
-    - swh.loader.package.arch.tasks.LoadArch
-    - swh.loader.package.archive.tasks.LoadArchive
-    - swh.loader.package.aur.tasks.LoadAur
-    - swh.loader.package.cpan.tasks.LoadCpan
-    - swh.loader.package.cran.tasks.LoadCRAN
-    - swh.loader.package.crates.tasks.LoadCrates
-    - swh.loader.package.debian.tasks.LoadDebian
-    - swh.loader.package.golang.tasks.LoadGolang
-    - swh.loader.package.hackage.tasks.LoadHackage
-    - swh.loader.package.maven.tasks.LoadMaven
-    - swh.loader.package.nixguix.tasks.LoadNixguix
-    - swh.loader.package.npm.tasks.LoadNpm
-    - swh.loader.package.opam.tasks.LoadOpam
-    - swh.loader.package.pubdev.tasks.LoadPubDev
-    - swh.loader.package.puppet.tasks.LoadPuppet
-    - swh.loader.package.pypi.tasks.LoadPyPI
-    - swh.loader.package.rubygems.tasks.LoadRubyGems
-    - swh.loader.svn.tasks.DumpMountAndLoadSvnRepository
-    - swh.loader.svn.tasks.LoadSvnRepository
-    - swh.loader.svn.tasks.MountAndLoadSvnRepository
-    - save_code_now:swh.loader.bzr.tasks.LoadBazaar
-    - save_code_now:swh.loader.cvs.tasks.LoadCvsRepository
-    - save_code_now:swh.loader.git.tasks.UpdateGitRepository
-    - save_code_now:swh.loader.mercurial.tasks.LoadArchiveMercurial
-    - save_code_now:swh.loader.mercurial.tasks.LoadMercurial
-    - save_code_now:swh.loader.svn.tasks.DumpMountAndLoadSvnRepository
-    - save_code_now:swh.loader.svn.tasks.MountAndLoadSvnRepository
-    - save_code_now:swh.loader.package.archive.tasks.LoadArchive
+    # - swh.loader.bzr.tasks.LoadBazaar
+    # - swh.loader.cvs.tasks.LoadCvsRepository
+    # - swh.loader.dir.tasks.LoadDirRepository
+    # - swh.loader.git.tasks.LoadDiskGitRepository
+    # - swh.loader.git.tasks.UncompressAndLoadDiskGitRepository
+    # - swh.loader.git.tasks.UpdateGitRepository
+    # - swh.loader.mercurial.tasks.LoadArchiveMercurial
+    # - swh.loader.mercurial.tasks.LoadMercurial
+    # - swh.loader.package.arch.tasks.LoadArch
+    # - swh.loader.package.archive.tasks.LoadArchive
+    # - swh.loader.package.aur.tasks.LoadAur
+    # - swh.loader.package.cpan.tasks.LoadCpan
+    # - swh.loader.package.cran.tasks.LoadCRAN
+    # - swh.loader.package.crates.tasks.LoadCrates
+    # - swh.loader.package.debian.tasks.LoadDebian
+    # - swh.loader.package.golang.tasks.LoadGolang
+    # - swh.loader.package.hackage.tasks.LoadHackage
+    # - swh.loader.package.maven.tasks.LoadMaven
+    # - swh.loader.package.npm.tasks.LoadNpm
+    # - swh.loader.package.opam.tasks.LoadOpam
+    # - swh.loader.package.pubdev.tasks.LoadPubDev
+    # - swh.loader.package.puppet.tasks.LoadPuppet
+    # - swh.loader.package.pypi.tasks.LoadPyPI
+    # - swh.loader.package.rubygems.tasks.LoadRubyGems
+    # - swh.loader.svn.tasks.DumpMountAndLoadSvnRepository
+    # - swh.loader.svn.tasks.LoadSvnRepository
+    # - swh.loader.svn.tasks.MountAndLoadSvnRepository
+    # - save_code_now:swh.loader.bzr.tasks.LoadBazaar
+    # - save_code_now:swh.loader.cvs.tasks.LoadCvsRepository
+    # - save_code_now:swh.loader.git.tasks.UpdateGitRepository
+    # - save_code_now:swh.loader.mercurial.tasks.LoadArchiveMercurial
+    # - save_code_now:swh.loader.mercurial.tasks.LoadMercurial
+    # - save_code_now:swh.loader.svn.tasks.DumpMountAndLoadSvnRepository
+    # - save_code_now:swh.loader.svn.tasks.MountAndLoadSvnRepository
+    # - save_code_now:swh.loader.package.archive.tasks.LoadArchive
+    - swh.loader.core.tasks.LoadContent
+    - swh.loader.core.tasks.LoadDirectory
diff --git a/docker/conf/scheduler.yml b/docker/conf/scheduler.yml
--- a/docker/conf/scheduler.yml
+++ b/docker/conf/scheduler.yml
@@ -6,4 +6,4 @@
   task_broker: amqp://guest:guest@amqp/%2f
   broker_transport_options:
     max_retries: 1
-no_origins_scheduled_backoff: 60
+no_origins_scheduled_backoff: 0