diff --git a/ansible/library/deb_alternatives.py b/ansible/library/deb_alternatives.py
new file mode 100644
index 0000000000000000000000000000000000000000..21dafd4b8bcb2f913aaa771ded79ecee4721d442
--- /dev/null
+++ b/ansible/library/deb_alternatives.py
@@ -0,0 +1,116 @@
+#!/usr/bin/python
+
+# based on
+# https://github.com/ansible-collections/community.general/blob/main/plugins/modules/system/alternatives.py
+
+import os
+import re
+import subprocess
+from ansible.module_utils.basic import AnsibleModule
+
+def main():
+
+ fields = {
+ "name": {"required": True, "type": "str"},
+ "path": {"required": True, "type": "path"},
+ "link": {"type": "path"},
+ "priority": {"type": "int", "default": 50},
+ "state": {"default": "set", "choices": ["present", "set", "auto"], "type": "str"},
+ "slaves": {"type": "list", "default": []}
+ }
+ module = AnsibleModule(argument_spec=fields, supports_check_mode=True)
+
+ params = module.params
+ name = params['name']
+ path = params['path']
+ link = params['link']
+ priority = params['priority']
+ state = params["state"]
+ slaves = params['slaves']
+
+ UPDATE_ALTERNATIVES = module.get_bin_path('update-alternatives', True)
+
+ current_path = None
+ all_alternatives = []
+
+ # Run `update-alternatives --display <name>` to find existing alternatives
+ (rc, display_output, dummy) = module.run_command(
+ ['env', 'LC_ALL=C', UPDATE_ALTERNATIVES, '--display', name]
+ )
+
+ if rc == 0:
+ # Alternatives already exist for this link group
+ # Parse the output to determine the current path of the symlink and
+ # available alternatives
+ current_path_regex = re.compile(r'^\s*link currently points to (.*)$',
+ re.MULTILINE)
+ alternative_regex = re.compile(r'^(\/.*)\s-\s(?:family\s\S+\s)?priority', re.MULTILINE)
+
+ match = current_path_regex.search(display_output)
+ if match:
+ current_path = match.group(1)
+ all_alternatives = alternative_regex.findall(display_output)
+
+ if not link:
+ # Read the current symlink target from `update-alternatives --query`
+ # in case we need to install the new alternative before setting it.
+ #
+ # This is only compatible on Debian-based systems, as the other
+ # alternatives don't have --query available
+ rc, query_output, dummy = module.run_command(
+ ['env', 'LC_ALL=C', UPDATE_ALTERNATIVES, '--query', name]
+ )
+ if rc == 0:
+ for line in query_output.splitlines():
+ if line.startswith('Link:'):
+ link = line.split()[1]
+ break
+
+ if current_path != path or len(slaves): # TODO: properly check changed status in presence of slaves
+ if module.check_mode:
+ module.exit_json(changed=True, current_path=current_path, slaves=slaves)
+ try:
+ # install the requested path if necessary
+ if path not in all_alternatives or len(slaves):
+ if not os.path.exists(path):
+ module.fail_json(msg="Specified path %s does not exist" % path)
+ if not link:
+ module.fail_json(msg="Needed to install the alternative, but unable to do so as we are missing the link")
+
+ cmd_slaves = []
+ SLAVE_KEYS = ["link", "name", "path"]
+ for slave in slaves:
+ for key in SLAVE_KEYS:
+ if key not in slave:
+ module.fail_json(msg="Key %s missing from slave list, required keys are: %s"
+ % (key, ", ".join(SLAVE_KEYS)))
+ cmd_slaves.extend(["--slave", slave["link"], slave["name"], slave["path"]])
+
+ module.run_command(
+ [UPDATE_ALTERNATIVES, '--install', link, name, path, str(priority)] + cmd_slaves,
+ check_rc=True
+ )
+
+ if state == "set":
+ # select the requested path
+ module.run_command(
+ [UPDATE_ALTERNATIVES, '--set', name, path],
+ check_rc=True
+ )
+
+ elif state == "auto":
+ # set the path to auto mode
+ module.run_command(
+ [UPDATE_ALTERNATIVES, '--auto', name],
+ check_rc=True
+ )
+
+ module.exit_json(changed=True, slaves=slaves)
+ except subprocess.CalledProcessError as cpe:
+ module.fail_json(msg=str(dir(cpe)))
+ else:
+ module.exit_json(changed=False, slaves=slaves)
+
+
+if __name__ == '__main__':
+ main()
diff --git a/ansible/roles/ghc_udeb/tasks/install.yml b/ansible/roles/ghc_udeb/tasks/install.yml
new file mode 100644
index 0000000000000000000000000000000000000000..322011f48fc397b8d78535cf6c788fc2ab42f547
--- /dev/null
+++ b/ansible/roles/ghc_udeb/tasks/install.yml
@@ -0,0 +1,125 @@
+---
+- name: Does GHC exist?
+ stat:
+ path: "/opt/ghc/{{version.ghc}}/bin/ghci-{{version.ghc}}"
+ register: ghc
+
+- name: Does Cabal exist?
+ stat:
+ path: "/opt/cabal/{{version.cabal}}/bin/cabal"
+ when: version.cabal is defined
+ register: cabal
+
+- name: GHC Dir
+ file:
+ state: directory
+ path: "/opt/ghc/{{version.ghc}}"
+
+- name: Cabal Dir
+ file:
+ state: directory
+ path: "/opt/cabal/{{version.cabal}}/bin"
+ when: version.cabal is defined
+
+- name: Build GHC & cabal if it does not exist
+ block:
+ - name: Build GHC under the builder user
+ block:
+ - name: "Download GHC"
+ unarchive:
+ src: 'https://downloads.haskell.org/~ghc/{{version.ghc}}/ghc-{{version.ghc}}-x86_64-deb9-linux.tar.xz'
+ dest: "/home/builder/ghc/"
+ remote_src: True
+
+ - name: Build GHC
+ shell:
+ chdir: '/home/builder/ghc/ghc-{{version.ghc}}'
+ cmd: "./configure --prefix=/opt/ghc/{{version.ghc}}/"
+ become_user: builder
+ become: true
+
+ - name: Install GHC
+ shell:
+ chdir: '/home/builder/ghc/ghc-{{version.ghc}}'
+ cmd: make install -j8
+
+ when: not ghc.stat.exists
+
+- name: Add cabal
+ unarchive:
+ src: "https://downloads.haskell.org/~cabal/cabal-install-{{version.cabal}}/cabal-install-{{version.cabal}}-x86_64-linux-deb10.tar.xz"
+ dest: "/opt/cabal/{{version.cabal}}/bin/"
+ remote_src: true
+ when: version.cabal is defined and not cabal.stat.exists
+
+- name: Setup opt-GHC alteranative
+ deb_alternatives:
+ name: "opt-ghc{{item}}"
+ link: "/opt/ghc/bin/ghc{{item}}"
+ path: "/opt/ghc/{{version.ghc}}/bin/ghc"
+ priority: "{{version_idx + 100}}"
+ state: present
+ slaves:
+ - link: "/opt/ghc/bin/ghci{{item}}"
+ name: "opt-ghci{{item}}"
+ path: "/opt/ghc/{{version.ghc}}/bin/ghci"
+ - link: "/opt/ghc/bin/runghc{{item}}"
+ name: "opt-runghc{{item}}"
+ path: "/opt/ghc/{{version.ghc}}/bin/runghc"
+ - link: "/opt/ghc/bin/ghc-pkg{{item}}"
+ name: "opt-ghc-pkg{{item}}"
+ path: "/opt/ghc/{{version.ghc}}/bin/ghc-pkg"
+ - link: "/opt/ghc/bin/haddock{{item}}"
+ name: "opt-haddock{{item}}"
+ path: "/opt/ghc/{{version.ghc}}/bin/haddock"
+ loop:
+ - ""
+ - "-{{version.ghc}}"
+
+- name: Setup GHC alternative
+ deb_alternatives:
+ name: "ghc{{item}}"
+ link: "/usr/bin/ghc{{item}}"
+ path: "/etc/alternatives/opt-ghc{{item}}"
+ priority: 100
+ state: present
+ slaves:
+ - link: "/usr/bin/ghci{{item}}"
+ name: "ghci{{item}}"
+ path: "/etc/alternatives/opt-ghci{{item}}"
+ - link: "/usr/bin/runghc{{item}}"
+ name: "runghc{{item}}"
+ path: "/etc/alternatives/opt-runghc{{item}}"
+ - link: "/usr/bin/ghc-pkg{{item}}"
+ name: "ghc-pkg{{item}}"
+ path: "/etc/alternatives/opt-ghc-pkg{{item}}"
+ - link: "/usr/bin/haddock{{item}}"
+ name: "haddock{{item}}"
+ path: "/etc/alternatives/opt-haddock{{item}}"
+ loop:
+ - ""
+ - "-{{version.ghc}}"
+
+- name: Setup opt-cabal alternative
+ deb_alternatives:
+ name: "opt-cabal{{item}}"
+ link: "/opt/ghc/bin/cabal{{item}}"
+ path: "/opt/cabal/{{version.cabal}}/bin/cabal"
+ priority: "{{version_idx + 100}}"
+ state: present
+ loop:
+ - ""
+ - "-{{version.cabal}}"
+ when: version.cabal is defined
+
+- name: Setup cabal alternative
+ deb_alternatives:
+ name: "cabal{{item}}"
+ link: "/usr/bin/cabal{{item}}"
+ path: "/etc/alternatives/opt-cabal{{item}}"
+ priority: 100
+ state: present
+ loop:
+ - ""
+ - "-{{version.cabal}}"
+ when: version.cabal is defined
diff --git a/ansible/roles/ghc_udeb/tasks/main.yml b/ansible/roles/ghc_udeb/tasks/main.yml
new file mode 100644
index 0000000000000000000000000000000000000000..77eef4f5f250b0f15edc871114d062920eabcb18
--- /dev/null
+++ b/ansible/roles/ghc_udeb/tasks/main.yml
@@ -0,0 +1,19 @@
+---
+- name: Builder user
+ user:
+ name: builder
+ create_home: true
+ shell: /bin/bash
+ system: true
+
+- name: GHC source dir
+ file:
+ state: directory
+ owner: "builder"
+ path: "/home/builder/ghc"
+
+- include_tasks: install.yml
+ loop: "{{versions}}"
+ loop_control:
+ loop_var: version
+ index_var: version_idx