diff --git a/.github/workflows/build.yml b/.github/workflows/build.yml
new file mode 100644
index 0000000..04f2a2e
--- /dev/null
+++ b/.github/workflows/build.yml
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+name: Build cache
+
+on:
+  workflow_dispatch: {}
+  push:
+    branches:
+    - main
+    paths:
+    - ubuntu-22.04/**
+  schedule:
+    - cron: "0 0 * * *"
+
+jobs:
+  build:
+    runs-on: ubuntu-22.04
+    permissions:
+      packages: write
+
+    steps:
+    - name: Checkout code
+      uses: actions/checkout@v2
+
+    - name: Setup spack
+      uses: spack/setup-spack@v2.1.1
+      with:
+        ref: develop
+
+    - name: Add mochi-spack-packages
+      run: |
+        git clone https://github.com/mochi-hpc/mochi-spack-packages
+        spack -e ubuntu-22.04 repo add mochi-spack-packages
+
+    - name: Install spack environment
+      run: |
+        spack -e ubuntu-22.04 install
+
+    - name: Show spack-installed packages
+      run: |
+        spack -e ubuntu-22.04 find -dlv
+
+    - name: Push packages to buildcache and update index
+      if: ${{ !cancelled() }}
+      run: |
+        spack -e ubuntu-22.04 mirror set --push \
+          --oci-username ${{ github.actor }} \
+          --oci-password "${{ secrets.GITHUB_TOKEN }}" mochi-buildcache
+        spack -e ubuntu-22.04 buildcache push --base-image ubuntu:22.04 \
+          --unsigned --update-index mochi-buildcache
diff --git a/README.md b/README.md
new file mode 100644
index 0000000..ac9e022
--- /dev/null
+++ b/README.md
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+# Mochi Spack Buildcache
+
+This repository is a mirror of pre-built Mochi spack packages.
+
+## How to use
+
+To use this mirror, you may use the following command with spack to
+make the mirror available globally to all your spack environments.
+
+```
+$ spack mirror add --unsigned mochi oci://ghcr.io/mochi-hpc/mochi-spack-buildcache
+```
+
+Alternatively, you can also add the following in a spack.yaml
+file for an environment. This will make the mirror visible to that
+environment only.
+
+```
+spack:
+  ...
+  mirror:
+    mochi:
+      url: oci://ghcr.io/mochi-hpc/mochi-spack-buildcache
+      signed: false
+```
+
+## Contributing
+
+### From another Mochi repository
+
+To allow another repository inside the [mochi-hpc](https://github.com/mochi-hpc)
+organization to push specs to the buildcache from a github action,
+follow the steps hereafter.
+
+First, navigate to the buildcache's
+[settings](https://github.com/orgs/mochi-hpc/packages/container/mochi-spack-buildcache/settings)
+and on the right of Manage Actions access, click the Add Repository button. Select the
+repository to add, and once it appears on the list bellow, change its role to "Write".
+
+Then, in your project's github repository, write a `spack.yaml` file to be used
+for building your project's dependencies. Here is an example to start from:
+
+```
+spack:
+    specs:
+    - mochi-margo
+    - mercury~checksum~boostsys ^libfabric fabrics=tcp,rxm
+    concretizer:
+      unify: true
+      reuse: true
+    modules:
+      prefix_inspections:
+        lib: [LD_LIBRARY_PATH]
+        lib64: [LD_LIBRARY_PATH]
+    mirrors:
+      mochi:
+        url: oci://ghcr.io/mochi-hpc/mochi-spack-buildcache
+        signed: false
+    config:
+      install_tree:
+        padded_length: 128
+```
+
+Make sure the mochi mirror is listed and `config:install_tree:padded_length` is set to 128.
+Add any specs you may need. This environment file will allow github actions that use it to
+rely on the buildcache to pull dependencies.
+
+Finally, here is an example of a github action that installs an environment
+from the spack.yaml file (which is assumed to live in a `tests` folder, but
+you can change that in via the `ENVNAME` environment variable at the beginning
+of the file) and pushes its installed specs to the cache.
+
+```
+name: Build
+
+env:
+  ENVNAME: tests
+
+on:
+  workflow_dispatch: {}
+  push:
+    branches:
+    - main
+  pull_request:
+    branches:
+    - main
+
+jobs:
+  build:
+    runs-on: ubuntu-22.04
+    permissions:
+      packages: write
+    steps:
+    - name: Checkout code
+      uses: actions/checkout@v2
+
+    - name: Setup spack
+      uses: spack/setup-spack@v2.1.1
+      with:
+        ref: develop
+        color: true
+        path: spack
+
+    - name: Add mochi-spack-packages
+      run: |
+        git clone https://github.com/mochi-hpc/mochi-spack-packages
+        spack -e $ENVNAME repo add mochi-spack-packages
+
+    - name: Install spack environment
+      run: |
+        spack -e $ENVNAME install
+
+    - name: Show spack-installed packages for debugging
+      run: |
+        spack -e $ENVNAME find -dlv
+
+    - name: Extra steps
+      run: |
+        echo "Put more steps here such as building/testing your code"
+
+    - name: Push packages to buildcache and update index
+      if: ${{ !cancelled() }}
+      run: |
+        spack -e $ENVNAME mirror set --push \
+          --oci-username ${{ github.actor }} \
+          --oci-password "${{ secrets.GITHUB_TOKEN }}" mochi
+        spack -e $ENVNAME buildcache push --base-image ubuntu:22.04 \
+          --unsigned --update-index mochi
+```
+
+### Manually
+
+You may sometimes want to manually push some specs to the cache, for
+instance if these specs have been build on a supercomputer and you want
+to cache them. To do so, follow the steps hereafter.
+
+First, you need to be a member of the
+[mochi-buildcache-maintainers](https://github.com/orgs/mochi-hpc/teams/mochi-buildcache-maintainers)
+team. If you are not, request to be added by posting an issue on this repository.
+
+Second, in your [Developer Settings](https://github.com/settings/apps),
+click "Personal access tokens" on the left, then "Tokens (classic)".
+Click "Generate new token" > "Generate new token (classic)".
+Call your token `MOCHI_BUILDCACHE_TOKEN`, set an appropriate expiration,
+then select `write:packages` as scope. Click the "Generate token" button at
+the bottom of the page, then copy your token.
+
+Warning: tokens are like passwords that, combined with your username,
+will allow anyone who has it to perform the operations it was given the scope for.
+Hence, make sure not to publish your token anywhere public and if you do by mistake,
+revoke the token immediately by going back to the above page and deleting it.
+
+Now that you have your token, create an environment from a `spack.yaml` file
+(see above for an example, make sure you have the `mirrors` entry and the
+ `config:install_tree:padded_length` set to 128). Activate your environment
+and install the specs that it defines.
+
+Still with the environment activated, you can now add the token to your mirror
+setup as follows (replacing `<username>` and `<token>` with your github username
+and your generated token).
+
+```
+$ spack mirror set --push --oci-username <username> --oci-password <token> mochi
+```
+
+This will add the token (in clear) in a file in the currently activated
+environment, hence remember the warning above and make sure that your spack
+installation (or wherever your environment lives) is correctly protected.
+
+You can now push push specs into the buildcache.
+
+```
+$ spack buildcache push --update-index --unsigned mochi <specs...>
+```
+
+Ommitting the specs will push all the specs from the environment.
+
+For a more details about the way buildcache work, please refer to
+the [spack documentation](https://spack.readthedocs.io/en/latest/binary_caches.html).
diff --git a/ubuntu-22.04/spack.yaml b/ubuntu-22.04/spack.yaml
new file mode 100644
index 0000000..e81545f
--- /dev/null
+++ b/ubuntu-22.04/spack.yaml
@@ -0,0 +1,39 @@
+# This file defines the spack environment used by github actions
+# (tests, codeql, and codecov) when building and testing the code.
+# In particular the "config" field sets the installation path and
+# spack caches to ~/.spack-ci so that they can be retrieved using
+# the github cache action across runs.
+spack:
+  specs:
+  - mochi-margo
+  - mochi-thallium
+  - mochi-abt-io
+  - mochi-ch-placement
+  - mercury~checksum~boostsys
+  - libfabric fabrics=tcp,rxm
+  - mochi-bedrock+abtio+ssg+mona+mpi
+  - mochi-mona
+  - mochi-poesie+lua+python~js+bedrock
+  - mochi-remi+bedrock
+  - mochi-ssg+mpi
+  - mochi-warabi+bedrock+remi
+  - mochi-yokan+bedrock+remi+berkeleydb+leveldb+lmdb+rocksdb+tkrzw+gdbm+unqlite+lua+python
+  - py-mochi-margo
+  concretizer:
+    unify: when_possible
+    reuse: dependencies
+  modules:
+    prefix_inspections:
+      lib: [LD_LIBRARY_PATH]
+      lib64: [LD_LIBRARY_PATH]
+  mirrors:
+    mochi-buildcache:
+      url: oci://ghcr.io/mochi-hpc/mochi-spack-buildcache
+      signed: false
+  config:
+    install_tree:
+      padded_length: 128
+  packages:
+    all:
+      providers:
+        mpi: [ mpich ]