Merge branch 'fix_permissions' into 'main'

Fix systemd config permissions

See merge request qontainers/pipglr!45

.gitignore

@@ -1 +0,0 @@
-/.pre-commit-config.yaml

.gitlab-ci.yml

@@ -1,10 +1,21 @@
 ---
 
 default:
-  image: quay.io/buildah/stable:v1.31.0
+  image: quay.io/buildah/stable:v1.32
   tags:
-    - docker
+    - saas-linux-small-amd64
-    - linux
+
+workflow:
+  rules:
+    - if: $CI_PIPELINE_SOURCE == "merge_request_event"
+    - if: $CI_COMMIT_BRANCH && $CI_OPEN_MERGE_REQUESTS
+      when: never
+    - if: $CI_COMMIT_BRANCH
+
+include:
+  - component: gitlab.com/blue42u/ci.pre-commit/lite@0.2.0
+    inputs:
+      job_stage: test
 
 envars:
   stage: test
@@ -14,6 +25,9 @@ envars:
 
 commit_check:
   stage: test
+  rules:
+    - if: $CI_PIPELINE_SOURCE == "merge_request_event"
+    - when: never
   variables:
     BADRX: '^(squash!)|(fixup!)'
   script: |
@@ -26,6 +40,8 @@ commit_check:
     fi
 
 build:
+  tags:
+    - saas-linux-medium-amd64
   stage: deploy
   variables:
     BUILDAH_FORMAT: docker

.pre-commit-config.yaml

@@ -0,0 +1,48 @@
+default_language_version:
+  python: python3
+default_install_hook_types: [pre-commit, commit-msg]
+default_stages: [pre-commit]
+
+repos:
+  - repo: https://github.com/executablebooks/mdformat
+    rev: '0.7.17'
+    hooks:
+    - id: mdformat
+      additional_dependencies:
+      - mdformat-footnote
+      - mdformat-tables
+
+  - repo: https://github.com/pre-commit/pre-commit-hooks
+    rev: v4.5.0
+    hooks:
+      - id: trailing-whitespace
+      - id: end-of-file-fixer
+      - id: fix-byte-order-marker
+      - id: mixed-line-ending
+      - id: check-executables-have-shebangs
+      - id: check-symlinks
+      - id: destroyed-symlinks
+      - id: check-merge-conflict
+      - id: check-case-conflict
+      - id: no-commit-to-branch
+        args: [--branch, main]
+      - id: check-yaml
+
+  - repo: https://github.com/python-jsonschema/check-jsonschema
+    rev: '0.28.0'
+    hooks:
+      # Validate the GitLab CI scripts against the schema. Doesn't catch everything but helps.
+      - id: check-gitlab-ci
+        files: '.*\.gitlab-ci\.yml$'
+
+  - repo: https://github.com/jumanjihouse/pre-commit-hooks
+    rev: '3.0.0'
+    hooks:
+      - id: forbid-binary
+      - id: require-ascii
+
+  - repo: meta
+    hooks:
+      # Un-comment (maybe temporarily) to check which hooks don't apply.
+      # - id: check-hooks-apply
+      - id: check-useless-excludes

Containerfile

@@ -24,7 +24,7 @@ ADD /home/ /home/
 # an incompatible change be introduced.
 ARG RUNNER_VERSION=latest
 
-# Permit building containers for alternate architectures.  At the time
+# Permit building containers for alternate architectures. At the time
 # of this commit, only 'arm64' is available.
 ARG TARGETARCH=amd64
 
@@ -45,10 +45,17 @@ ENTRYPOINT /lib/systemd/systemd
 # Gitlab-runner configuration options, may be freely overridden at
 # container image build time.
 ARG DEFAULT_JOB_IMAGE=registry.fedoraproject.org/fedora-minimal:latest
+
+# Allow image-builders to override the Gitlab URL
+ARG GITLAB_URL=https://gitlab.com/
+
 # Run nested containers in --privileged mode - required to allow building
 # container images using podman or buildah.  Otherwise may be set 'false'.
 ARG NESTED_PRIVILEGED=true
 
+# Download the FIPS version of gitlab-runner when enabled on the host system.
+ARG ENABLE_FIPS=true
+
 # The registration runlabel may be called multiple times to register more than
 # one runner.  Each expects a REGISTRATION_TOKEN secret to be pre-defined and
 # the file './config.toml' to exist (may be empty).  A local-cache volume
@@ -59,11 +66,10 @@ LABEL register="podman run -it --rm \
  --secret=REGISTRATION_TOKEN,type=env \
  -v ./config.toml:/etc/gitlab-runner/config.toml:Z \
  -e REGISTER_NON_INTERACTIVE=true \
- -e CI_SERVER_URL=https://gitlab.com/ \
+ -e CI_SERVER_URL=${GITLAB_URL} \
  -e RUNNER_NAME=pipglr \
  -e RUNNER_EXECUTOR=docker \
  -e RUNNER_SHELL=bash \
- -e REGISTER_MAINTENANCE_NOTE=Podman-In-Podman-GitLab-Runner \
  -e DOCKER_HOST=unix:///home/runner/podman.sock \
  -e DOCKER_IMAGE=${DEFAULT_JOB_IMAGE} \
  -e DOCKER_CACHE_DIR=/cache \
@@ -71,17 +77,21 @@ LABEL register="podman run -it --rm \
  -e DOCKER_NETWORK_MODE=host \
  -e DOCKER_PRIVILEGED=${NESTED_PRIVILEGED} \
  --entrypoint=/usr/bin/gitlab-runner \$IMAGE register"
+
 # Additionally, the nested-podman storage volumes must be pre-created with
 # 'podman' UID/GID values to allow nested containers access.
 LABEL setupstorage="podman volume create --opt o=uid=1000,gid=1000 pipglr-storage"
+
 # Lastly, the gitlab-runner will manage container-cache in this directory,
 # which will also be bind-mounted into every container.  So it must be
 # writable by both 'podman' user and 'runner' group.
 LABEL setupcache="podman volume create --opt o=uid=1000,gid=1001 pipglr-cache"
+
 # Helper to extract the current configuration secret to allow editing.
 LABEL dumpconfig="podman run -it --rm \
  --secret config.toml --entrypoint=/bin/cat \
  \$IMAGE /var/run/secrets/config.toml"
+
 # Executing the runner container depends on the config.toml secret being
 # set (see above) and two volumes existing with correct permissions set.
 # Note: The contents of the volumes are not critical, they may be removed
@@ -92,3 +102,4 @@ LABEL run="podman run -dt --name pipglr \
  -v pipglr-cache:/cache \
  --systemd true --privileged \
  --device /dev/fuse \$IMAGE"
+# ==========================

README.md

@@ -1,79 +1,84 @@
+# Podmand-In-Podman Gitlab Runner
+
+This project provides a Gitlab Runner which runs inside a container launched
+with `podman`. The Gitlab Runner itself uses an independent `podman` instance
+inside to launch jobs.
+
 ## Overview
 
-This container image is built daily from this `Containerfile`, and
+This container image is built weekly from this `Containerfile`, and made
-made available as:
+available as:
 
-* `registry.gitlab.com/qontainers/pipglr:latest`
+- `registry.gitlab.com/qontainers/pipglr:latest`
 
 -or-
 
-* `registry.gitlab.com/qontainers/pipglr:<version>`
+- `registry.gitlab.com/qontainers/pipglr:<version>`
 
-It's purpose is to provide an easy method to execute a GitLab runner,
+It's purpose is to provide an easy method to execute a GitLab runner, to service
-to service CI/CD jobs for groups and/or repositories on
+CI/CD jobs for groups and/or repositories on [gitlab.com](https://gitlab.com).
-[gitlab.com](https://gitlab.com).  It comes pre-configured to utilize
+It comes pre-configured to utilize the gitlab-runner app to execute within a
-the gitlab-runner app to execute within a rootless podman container,
+rootless podman container, nested inside a rootless podman container.
-nested inside a rootless podman container.
 
-This is intended to provide additional layers of security for the host,
+This is intended to provide additional layers of security for the host, when
-when running potentially arbitrary CI/CD code.  Though, the ultimate
+running potentially arbitrary CI/CD code. Though, the ultimate responsibility
-responsibility still rests with the end-user to review the setup and
+still rests with the end-user to review the setup and configuration relative to
-configuration relative to their own security situation/environment.
+their own security situation/environment.
 
-**Note**: While this can run entirely under a regular user, it will require
+**Note**: While this can run entirely under a regular user, it will require root
-root access for the first two setup steps (below).
+access for the first two setup steps (below).
 
 ### Operation
 
-This image leverages the podman `runlabel` feature heavily.  Several
+This image leverages the podman `runlabel` feature heavily. Several labels are
-labels are set on the image to support easy registration and execution
+set on the image to support easy registration and execution of the runner
-of the runner container.  While it's possible to use the container
+container. While it's possible to use the container with your own command-line,
-with your own command-line,  it's highly recommended to base them
+it's highly recommended to base them off of one of the labels. See the examples
-off of one of the labels.  See the examples below for more information.
+below for more information.
 
-***Note:*** Some older versions of podman don't support the
+**_Note:_** Some older versions of podman don't support the `container runlabel`
-`container runlabel` sub-command.  If this is the case, you may simulate
+sub-command. If this is the case, you may simulate it with the following,
-it with the following, substituting `<label>` with one of the predefined
+substituting `<label>` with one of the predefined values (i.e. `register`,
-values (i.e. `register`, `setupconfig`, etc.):
+`setupconfig`, etc.):
 
 ```bash
 $ IMAGE="registry.gitlab.com/qontainers/pipglr:latest"
 $ eval $(podman inspect --format=json $IMAGE | jq -r .[].Labels.<label>)
 ```
 
-#### Persistent containers (step 1)
+#### Persistent Containers (step 1)
 
 By default on many distributions, regular users aren't permitted to leave
-background processes running after they log out.  Since this is likely
+background processes running after they log out. Since this is likely desired
-desired for running the pipglr container long-term, `systemd` needs to be
+for running the pipglr container long-term, `systemd` needs to be configured to
-configured to override this policy.  For this, you (`$USER`) will need
+override this policy. For this, you (`$USER`) will need root access on the
-root access on the system.
+system.
 
 ```bash
 $ sudo loginctl enable-linger $USER
 ```
 
 Side-effect: This will allow your user to persist other user-level systemd
-services as well.  For example `podman.socket` is handy to enable for
+services as well. For example `podman.socket` is handy to enable for
-`podman remote` access.  You could also [setup
+`podman remote` access. You could also
-quadlet](https://www.redhat.com/sysadmin/quadlet-podman) or a systemd unit
+[setup quadlet](https://www.redhat.com/sysadmin/quadlet-podman) or a systemd
-so pipglr starts up on system boot.
+unit so pipglr starts up on system boot.
 
-#### Expanded user-namespace (step 2) ***This is probably important***
+#### Expanded User-Namespace (step 2) **_This is probably important_**
 
-As an added protection/safety measure, pipglr excludes three UID/GIDs
+As an added protection/safety measure, pipglr excludes three UID/GIDs from being
-from being used by job-level containers.  One for `root`, another for
+used by job-level containers. One for `root`, another for `runner` and a third
-`runner` and a third for `podman`.  However, some container images
+for `podman`. However, some container images you may want to use for jobs
-you may want to use for jobs (mainly Debian/Ubuntu), assign one/more
+(mainly Debian/Ubuntu), assign one/more essential users a high UID/GID value
-essential users a high UID/GID value (like `65535`).
+(like `65535`).
 
 At the same time, most distributions also set `65536` as the default maximum
-number (including ID `0`) of IDs to allocate for user-namespaces (via `/etc/login.defs`).  This
+number (including ID `0`) of IDs to allocate for user-namespaces (via
-creates a problem you won't realize until the runner actually picks up a job
+`/etc/login.defs`). This creates a problem you won't realize until the runner
-😞 The main symptom of this issue will be messages in the pipglr containers log,
+actually picks up a job. The main symptom of this issue will be messages in
-similar to (abbreviated):
+the pipglr containers log, similar to (abbreviated):
 
-```
+```text
 ...cut...
 running `/usr/bin/newuidmap ...cut...`: newuidmap: write to uid_map failed: Operation not permitted
 Error: cannot set up namespace using "/usr/bin/newuidmap": exit status 1
@@ -82,66 +87,71 @@ Error: cannot set up namespace using "/usr/bin/newuidmap": exit status 1
 
 or
 
-```
+```text
 E: setgroups 65534 failed - setgroups (22: Invalid argument)
 ```
 
-***The good news is, working around this is relatively simple:***
+**_The good news is, working around this is relatively simple:_**
 
-As root, edit the two files `/etc/subuid` and `/etc/subgid` to expand the
+As root, edit the two files `/etc/subuid` and `/etc/subgid` to expand the by 3
-by 3 IDs.  For example assuming a user running the pipglr container is
+IDs. For example assuming a user running the pipglr container is called
-called `johndoe`, the contents of these files should be edited to allocate
+`johndoe`, the contents of these files should be edited to allocate `65539` IDs
-`65539` IDs like:
+like:
 
-`jogndoe:<some number>:65539`
+`johndoe:<some number>:65539`
 
 Where `<some number>` was set by your OS when the `johndoe` user was created
-(you can ignore this).  Only the last number needs to be increased.
+(you can ignore this). Only the last number needs to be increased. This change
+will be effective on next login, or immediately by running:
 
-#### Runner registration (step 3)
+`podman system migrate`
 
-All runners must be connected to a project or group runner configuration
+_Note:_ This will stop any currently running containers.
-on your gitlab instance (or `gitlab.com`).  This is done using a special
-registration *runlabel*.  The command can (and probably should) be run
-more than once (using the same `config.toml`) to configure and register
-multiple runners.  This is necessary for the *pipglr* container to execute
-multiple jobs in parallel.  For example, if you want to support running
-four jobs at the same time, you would use the `register` *runlabel*
-four times.
 
-Before using the `register`  *runlabel*, you must set your unique
+#### Runner Registration (step 3)
-*registration* (a.k.a. *activation*) token as a podman *secret*.  This
+
-secret may be removed once the registration step is complete.  The
+All runners must be connected to a project or group runner configuration on your
-**<actual registration token>** value (below) should be replaced with
+gitlab instance (or `gitlab.com`). This is done using a special registration
-the value obtained from the "runners" settings page of a gitlab
+_runlabel_. The command can (and probably should) be run more than once (using
-group or project's *CI/CD Settings*.  Gitlab version 16 and later
+the same `config.toml`) to configure and register multiple runners. This is
-refers to this value as an *activation* token, but the usage is the same.
+necessary for the _pipglr_ container to execute multiple jobs in parallel. For
+example, if you want to support running four jobs at the same time, you would
+use the `register` _runlabel_ four times.
+
+Before using the `register` _runlabel_, you must set your unique _registration_
+(a.k.a. _activation_) token as a podman _secret_. This secret may be removed
+once the registration step is complete. The **`<actual registration token>`**
+value (below) should be replaced with the value obtained from the `runners`
+settings page of a gitlab group or project's _CI/CD Settings_. Gitlab version 16
+and later refers to this value as an _activation_ token, but the usage is the
+same.
 
 ```bash
 $ IMAGE="registry.gitlab.com/qontainers/pipglr:latest"
 $ echo '<actual registration token>' | podman secret create REGISTRATION_TOKEN -
 ```
 
-Next, ***a blank `config.toml` file*** needs to be created.  Without this, the
+Next, **_a blank `config.toml` file_** needs to be created. Without this, the
-`reigster` *runlabel* will return a permission-denied error.  Once the empty
+`reigster` _runlabel_ will return a permission-denied error. Once the empty
 `config.toml` file is created, you may register one or more runners by repeating
-the registration *runlabel* as follows:
+the registration _runlabel_ as follows:
 
 ```bash
 $ IMAGE="registry.gitlab.com/qontainers/pipglr:latest"
 $ touch ./config.toml  # important: file must exist, even if empty.
 $ podman container runlabel register $IMAGE
-...repeat as desired...
+# ...repeat as desired...
 $ podman secret rm REGISTRATION_TOKEN  # if desired
 ```
 
 #### Runner Configuration (step 4)
 
-During the registration process (above), a boiler-plate (default) `config.toml` file
+During the registration process (above), a boiler-plate (default) `config.toml`
-will be created/updated for you.  At this point you may edit the configuration
+file will be created/updated for you. At this point you may edit the
-if desired before committing it as a *podman secret*.  Please refer to the
+configuration if desired before committing it as a _podman secret_. Please refer
-[gitlab runner documentation](https://docs.gitlab.com/runner/configuration/)
+to the
-for details.
+[gitlab runner documentation](https://docs.gitlab.com/runner/configuration/) for
+details.
 
 ```bash
 $ $EDITOR ./config.toml  # if desired
@@ -150,15 +160,15 @@ $ rm ./config.toml  # if desired
 ```
 
 This may be necessary, for example, to increase the default `concurrency` value
-to reflect the number of registered runners.  If you need to edit this file
+to reflect the number of registered runners. If you need to edit this file after
-after committing it as a secret, there's
+committing it as a secret, there's
-[ a `dumpconfig`  *runlabel* for that](README.md#configuration-editing).
+[a `dumpconfig` _runlabel_ for that](README.md#configuration-editing).
 
-#### Volume setup (step 5)
+#### Volume Setup (step 5)
 
 Since several users are utilized inside the container volumes must be
-specifically configured to permit access.  This is done using several
+specifically configured to permit access. This is done using several _runlabels_
-*runlabels* as follows:
+as follows:
 
 ```bash
 $ IMAGE="registry.gitlab.com/qontainers/pipglr:latest"
@@ -166,16 +176,17 @@ $ podman container runlabel setupstorage $IMAGE
 $ podman container runlabel setupcache $IMAGE
 ```
 
-Note: These volumes generally do not contain any critical operational data,
+Note: These volumes generally do not contain any critical operational data, they
-they may be re-created anytime to quickly free up host disk-space if
+may be re-created anytime to quickly free up host disk-space if it's running
-it's running low.  Simply remove them with the command
+low. Simply remove them with the command
- `podman volume rm pipglr-storage pipglr-cache`.  Then reuse the `setupstorage`
+`podman volume rm pipglr-storage pipglr-cache`. Then reuse the `setupstorage`
-and `setupcache` *runlabels* as in the above example.
+and `setupcache` _runlabels_ as in the above example.
 
 #### Runner Startup (step 6)
 
 With the runner configuration saved as a Podman secret, and the runner volumes
-created, the GitLab runner container may be launched with the following commands:
+created, the GitLab runner container may be launched with the following
+commands:
 
 ```bash
 $ IMAGE="registry.gitlab.com/qontainers/pipglr:latest"
@@ -184,11 +195,10 @@ $ podman container runlabel run $IMAGE
 
 ### Configuration Editing
 
-The gitlab-runner configuration contains some sensitive values which
+The gitlab-runner configuration contains some sensitive values which should be
-should be protected.  The pipglr container assumes the entire configuration
+protected. The pipglr container assumes the entire configuration will be passed
-will be passed in as a Podman secret.  This makes editing it slightly
+in as a Podman secret. This makes editing it slightly convoluted, so a handy
-convoluted, so a handy *runlabel* `dumpconfig` is available.
+_runlabel_ `dumpconfig` is available. It's intended use is as follows:
-It's intended use is as follows:
 
 ```bash
 $ IMAGE="registry.gitlab.com/qontainers/pipglr:latest"
@@ -201,17 +211,17 @@ $ rm ./config.toml  # if desired
 
 ### Debugging
 
-The first thing to check is the container output.  This shows three things:
+The first thing to check is the container output. This shows three things:
-Systemd, Podman, and GitLab-Runner output.  For example:
+Systemd, Podman, and GitLab-Runner output. For example:
 
 ```bash
 $ podman logs --since 0 pipglr
 ```
 
-Next, try running a pipglr image built with more verbose logging.  Both
+Next, try running a pipglr image built with more verbose logging. Both the
-the `runner.service` and `podman.service` files have a `log-level` option.
+`runner.service` and `podman.service` files have a `log-level` option. Simply
-Simply increase one or both to the "info", or "debug" level.  Start the
+increase one or both to the `info`, or `debug` level. Start the debug container,
-debug container, and reproduce the problem.
+and reproduce the problem.
 
 ## Building
 
@@ -221,37 +231,36 @@ This image may be built simply with:
 $ podman build -t registry.gitlab.com/qontainers/pipglr:latest .
 ```
 
-This will utilize the latest stable version of podman and the latest
+This will utilize the latest stable version of podman and the latest stable
-stable version of the gitlab runner.
+version of the gitlab runner.
 
-### Build-args
+### Build-Arguments
 
 Several build arguments are available to control the output image:
 
-* `PRUNE_INTERVAL` - A systemd.timer compatible `OnCalendar` value that
+- `PRUNE_INTERVAL`: A systemd.timer compatible `OnCalendar` value that
   determines how often to prune Podman's storage of disused containers and
-  images.  Defaults to "daily", but should be adjusted based on desired
+  images. Defaults to `daily`, but should be adjusted based on desired
-  caching-effect balanced against available storage space and job
+  caching-effect balanced against available storage space and job execution
-  execution rate.
+  rate.
-* `RUNNER_VERSION` - Allows specifying an exact gitlab runner version.
+- `RUNNER_VERSION`: Allows specifying an exact gitlab runner version. By default
-  By default the `latest` is used, assuming the user is building a tagged
+  the `latest` is used, assuming the user is building a tagged image anyway.
-  image anyway.  Valid versions may be found on the [runner
+  Valid versions may be found on the
-  release page](https://gitlab.com/gitlab-org/gitlab-runner/-/releases).
+  [runner release page](https://gitlab.com/gitlab-org/gitlab-runner/-/releases).
-* `TARGETARCH` - Supports inclusion of non-x86_64 gitlab runners.  This
+- `TARGETARCH`: Supports inclusion of non-x86_64 gitlab runners. This value is
-  value is assumed to match the image's architecture.  If using the
+  assumed to match the image's architecture. If using the `--platform` build
-  `--platform` build argument, it will be set automatically.  Note:
+  argument, it will be set automatically. Note: as of this writing, only `amd64`
-  as of this writing, only `amd64` and `arm64` builds of the gitlab-runner
+  and `arm64` builds of the gitlab-runner are available.
-  are available.
+- `GITLAB_URL`: Defaults to `https://gitlab.com/` but can be set to point to a
-* `NESTED_PRIVILEGED` - Defaults to 'true', may be set 'false' to prevent
+  self hosted instance of Gitlab.
-  nested containers running in `--privileged` mode.  This will affect
+- `NESTED_PRIVILEGED`: Defaults to `true`, may be set `false` to prevent nested
-  the ability to build container images in CI jobs using tools like
+  containers running in `--privileged` mode. This will affect the ability to
-  podman or buildah.
+  build container images in CI jobs using tools like podman or buildah.
 
-### Environment variables
+### Environment Variables
 
 Nearly every option to every gitlab-runner sub-command may be specified via
-environment variable.  Some of these are set in the `Containerfile` for
+environment variable. Some of these are set in the `Containerfile` for the
-the `register` *runlabel*.  If you need to set additional runtime
+`register` _runlabel_. If you need to set additional runtime env. vars., please
-env. vars., please do so via additional `Environment` optionns in the
+do so via additional `Environment` optionns in the `runner.service` file. See
-`runner.service` file.  See the *systemd.nspawn* man page for important
+the _systemd.nspawn_ man page for important value-format details.
-value-format details.

root/setup.sh

@@ -1,4 +1,5 @@
-
+#!/usr/bin/env bash
+#
 # This script is intended to be run during container-image build.  Any
 # other usage outside this context is likely to cause harm.
 #
@@ -20,117 +21,185 @@
 
 set -eo pipefail
 
-for varname in PRUNE_INTERVAL RUNNER_VERSION TARGETARCH; do
+function die() {
-  if [[ -z "${!varname}" ]]; then
+  echo -n '!! ERROR:' >&2
-    echo "Error: \$$varname must be non-empty."
+  printf "         %s\n" "$@" >&2
-  fi
-done
-
-# Make image smaller by not installing docs.
-DNF="dnf --setopt=tsflags=nodocs -y"
-
-for rpm in $(egrep -v '^(# )+' < /root/xpackages.txt); do
-  x+="--exclude=$rpm ";
-done
-
-set -x  # show what's happening to make debugging easier
-
-# DNF itself or a dependence may need upgrading, take care of it first.
-$DNF upgrade
-
-# WORKAROUND: crun: write to `/proc/self/oom_score_adj`: Permission denied
-# Ref: https://github.com/containers/podman/pull/19843
-if [[ $(date +%Y%m%d) -gt 20231115 ]]; then
-  echo "FIXME: Please check if crun 1.9.3+ is available in CentOS Stream-9."
-  echo "If so, this crun-1.8.7 workaround may be removed."
   exit 1
-fi
+}
-dnf $x install -y crun-1.8.7
 
-$DNF $x install \
+function check_vars() {
-  podman \
+  for varname in PRUNE_INTERVAL RUNNER_VERSION TARGETARCH; do
-  systemd
+    if [[ -z "${!varname}" ]]; then
+      die "Env. variable '$varname' must be non-empty."
+    fi
+  done
+}
+
+function main() {
+  # Show what's happening to make debugging easier
+  set -x
+
+  # Make image smaller by not installing docs.
+  dnf=(dnf --setopt=tsflags=nodocs -y)
+
+  install_packages
+  setup_user
+  setup_service_podman
+  setup_service_runner
+  setup_gitlab_config
+
+  finalize_ownership
+}
+
+function install_packages() {
+  readarray xpackages < <(grep -vE '^(# )+' </root/xpackages.txt)
+  local exclude_args=()
+  for rpm in "${xpackages[@]}"; do
+    exclude_args+=("--exclude=$rpm")
+  done
+
+  # DNF itself or a dependence may need upgrading, take care of it first.
+  "${dnf[@]}" upgrade &&
+    "${dnf[@]}" "${exclude_args[@]}" install \
+      podman \
+      systemd
+
+  # Gitlab-runner package contains scriptlets which do not function properly inside a
+  # container-build environment where systemd is not active/running.
+  if [[ ${ENABLE_FIPS} == true && $(cat /proc/sys/crypto/fips_enabled) == 1 ]]; then
+    PACKAGE_FILE="gitlab-runner_${TARGETARCH}-fips.rpm"
+  else
+    PACKAGE_FILE="gitlab-runner_${TARGETARCH}.rpm"
+  fi
+
+  "${dnf[@]}" "${exclude_args[@]}" \
+    --setopt=tsflags=noscripts install \
+    "https://gitlab-runner-downloads.s3.amazonaws.com/$RUNNER_VERSION/rpm/${PACKAGE_FILE}"
 
-# Gitlab-runner package contains scriptlets which do not function properly inside a
-# container-build environment where systemd is not active/running.
-$DNF $x --setopt=tsflags=noscripts install \
-  https://gitlab-runner-downloads.s3.amazonaws.com/$RUNNER_VERSION/rpm/gitlab-runner_${TARGETARCH}.rpm
 
 # Allow removing dnf, sudo, etc. packages.  Also don't start unnecessary or broken
 # systemd services, like anything kernel related or login gettys.
 rm -rf \
   /etc/dnf/protected.d/* \
-  /etc/sytemd/system/getty.target.wants/* \
+  /etc/systemd/system/getty.target.wants/* \
-  /etc/sytemd/system/multi-user.target.wants/* \
+  /etc/systemd/system/multi-user.target.wants/* \
-  /etc/sytemd/system/sysinit.target.wants/* \
+  /etc/systemd/system/sysinit.target.wants/* \
-  /etc/sytemd/system/timers.target.wants/* \
+  /etc/systemd/system/timers.target.wants/* \
   /lib/systemd/system/graphical.target.wants/* \
   /lib/systemd/system/multi-user.target.wants/{getty.target,systemd-ask-password-wall.path} \
   /lib/systemd/system/sys-kernel*.mount
 
-# Remove unnecessary packages, see xpackages.txt to learn how this list was generated.
+  # Allow removing dnf, sudo, etc. packages.
-# This makes the image smaller and reduces the attack-surface.
+  rm -rf \
-dnf remove -y $(egrep -v '^(# )+' /root/xpackages.txt)
+    /etc/dnf/protected.d/*
+  # Remove unnecessary packages, see xpackages.txt to learn how this list was generated.
+  # This makes the image smaller and reduces the attack-surface.
+  dnf remove -y "${xpackages[@]}"
 
-# Wipe out the DNF cache, then remove it entirely, again to make the image smaller.
+  # Wipe out the DNF cache, then remove it entirely, again to make the image smaller.
-$DNF clean all
+  "${dnf[@]}" clean all
-rm -rf /var/cache/dnf /var/log/dnf* /var/log/yum.*
+  rm -rf /var/cache/dnf /var/log/dnf* /var/log/yum.*
-rpm -e dnf
+  rpm -e dnf
 
-# Workaround https://bugzilla.redhat.com/show_bug.cgi?id=1995337
+  # Workaround base-image failing to confer capabilties properly on
-rpm --setcaps shadow-utils
+  # /usr/bin/new{u,g}idmap to `cap_set{u,g}id=ep` in new image layers.
+  rpm --setcaps shadow-utils
+}
 
-# Prevent copying of skel since it can interfere with the gitlab-runner
+function setup_user() {
-mkdir -p /home/podman /home/runner
+  # Guarantee uid/gid 1000 for user 'podman' / 1001 for user 'runner'.
-# Guarantee uid/gid 1000 for user 'podman' / 1001 for user 'runner'.
+  groupadd -g 1000 podman
-groupadd -g 1000 podman
+  groupadd -g 1001 runner
-groupadd -g 1001 runner
-# Separate users for services to increase process isolation.
-# The 'podman' user's socket service writes /home/runner/podman.socket
-useradd -M -u 1000 -g podman -G runner podman
-useradd -M -u 1001 -g runner runner
-# Allow 'podman' user to create socket file under /home/runner.
-chmod 770 /home/runner
 
-# Overwrite defaults, only user 'podman' permited to have a user-namespace
+  # Separate users for services to increase process isolation.
-# Split the namespaced ID's around the containers root (ID 0), podman (ID 1000), and
+  # The 'podman' user's socket service writes /home/runner/podman.socket
-# runner (ID 1001) such that the user-namespace of any nested containers cannot
+  # Prevent copying of skel since it can interfere with the gitlab-runner
-# read or write any files owned by these users (and/or hijack nested container processes).
+  mkdir -p /home/podman /home/runner
-# N/B: The range-end (999+64536) ensures a total of 65535 IDs are available for nested-containers.
+  useradd -M -u 1000 -g podman -G runner podman
-#      This requires the host provide a sufficiently large range, i.e. `pipglr:<start>:65539`
+  useradd -M -u 1001 -g runner runner
-echo -e "podman:1:999\npodman:1002:64536" | tee /etc/subuid > /etc/subgid
-# Host volume mount necessary for nested-podman to use overlayfs2 for container & volume storage.
-mkdir -p /home/podman/.local/share/containers
-# Nested-container's local container-cache volume mount, recommended by gitlab-runner docs.
-mkdir -p /cache
-# Both the gitlab-runner and podman need access to the cache directory / volume mount.
-chown podman:runner /cache
 
-# Setup persistent 'podman' user services to start & run without a login.
+  # Allow only podman in `/home/podman`.
-mkdir -p /var/lib/systemd/linger
+  chmod 700 /home/podman
-touch /var/lib/systemd/linger/podman
+  # Allow 'podman' user to create socket file under `/home/runner`.
-# Setup 'podman' socket and a container-storage pruning service for 'podman' user.
+  chmod 770 /home/runner
-mkdir -p /home/podman/.config/systemd/user/{sockets.target.wants,default.target.wants}
-cd /home/podman/.config/systemd/user/
-ln -s $PWD/podman.socket ./sockets.target.wants/     # Added from Containerfile
-ln -s $PWD/prune.timer ./default.target.wants/        # also from Containerfile
-# Substitute value from --build-arg if specified, otherwise use default from Containerfile.
-sed -i -e "s/@@@PRUNE_INTERVAL@@@/$PRUNE_INTERVAL/" ./prune.timer
-# Containerfile ADD instruction does not properly set ownership/permissions.
-chown -R 1000:1000 /home/podman
-chmod 700 /home/podman
 
-# Setup persistent 'runner' user services to start & run without a login.
+  # Set permissions.
-touch /var/lib/systemd/linger/runner
+  chown -R runner:runner /home/runner
-mkdir -p /home/runner/.config/systemd/user/default.target.wants
+  chown -R podman:podman /home/podman
-cd /home/runner/.config/systemd/user/
+
-# Does not depend on podman.socket file availablility, will retry if not present.
+  # Overwrite defaults, only user 'podman' permitted to have a user-namespace
-ln -s $PWD/runner.service ./default.target.wants/
+  # Split the namespaced ID's around the containers root (ID 0), podman (ID 1000), and
-# gitlab-runner will create side-car '.runner_system_id' file next to 'config.toml'
+  # runner (ID 1001) such that the user-namespace of any nested containers cannot
-# on first startup.  Ensure access is allowed.  Also link to future config file
+  # read or write any files owned by these users (and/or hijack nested container processes).
-# presented as a container-secret.
+  # N/B: The range-end (999+64536) ensures a total of 65535 IDs are available for nested-containers.
-mkdir -p /home/runner/.gitlab-runner
+  #      This requires the host provide a sufficiently large range, i.e. `pipglr:<start>:65539`
-ln -s /var/run/secrets/config.toml /home/runner/.gitlab-runner/config.toml
+  echo -e "podman:1:999\npodman:1002:64536" | tee /etc/subuid >/etc/subgid
-# Containerfile ADD instruction does not properly set ownership/permissions.
+}
-chown -R runner:runner /home/runner
+
-chmod -R 700 /home/runner/.gitlab-runner
+function setup_volumes() {
+  # Host volume mount necessary for nested-podman to use overlayfs2 for container & volume storage.
+  mkdir -p /home/podman/.local/share/containers
+
+  # Nested-container's local container-cache volume mount, recommended by gitlab-runner docs.
+  mkdir -p /cache
+
+  # Both the gitlab-runner and podman need access to the cache directory / volume mount.
+  chown podman:runner /cache
+}
+
+function setup_service_podman() {
+  # Setup persistent 'podman' user services to start & run without a login.
+  mkdir -p /var/lib/systemd/linger
+  touch /var/lib/systemd/linger/podman
+
+  # Setup 'podman' socket and a container-storage pruning service for 'podman' user.
+  mkdir -p /home/podman/.config/systemd/user/{sockets.target.wants,default.target.wants}
+
+  cd /home/podman/.config/systemd/user/
+  ln -s "$(pwd)/podman.socket" ./sockets.target.wants/ # Added from Containerfile
+  ln -s "$(pwd)/prune.timer" ./default.target.wants/   # also from Containerfile
+
+  # Substitute value from --build-arg if specified, otherwise use default from Containerfile.
+  sed -i -e "s/@@@PRUNE_INTERVAL@@@/$PRUNE_INTERVAL/" ./prune.timer
+}
+
+function setup_service_runner() {
+  # Setup persistent 'runner' user services to start & run without a login.
+  touch /var/lib/systemd/linger/runner
+
+  # Setup persistent 'runner' user services to start & run without a login.
+  mkdir -p /home/runner/.config/systemd/user/default.target.wants
+
+  cd /home/runner/.config/systemd/user/
+  # Does not depend on podman.socket file availability, will retry if not present.
+  ln -s "$(pwd)/runner.service" ./default.target.wants/
+}
+
+function setup_gitlab_config() {
+  # gitlab-runner will create side-car '.runner_system_id' file next to 'config.toml'
+  # on first startup.  Ensure access is allowed.  Also link to future config file
+  # presented as a container-secret.
+  mkdir -p /home/runner/.gitlab-runner
+  ln -s /var/run/secrets/config.toml /home/runner/.gitlab-runner/config.toml
+
+  chmod -R 700 /home/runner/.gitlab-runner
+}
+
+function finalize_ownership() {
+  # Adjust ownership to all files created after `setup_user`.
+  # and also to the `ADD` instruction in the `Containerfile`.
+  chown -R runner:runner /home/runner
+  chown -R podman:podman /home/podman
+
+  # Ensure correct permissions of system configuration files.
+  # Somehow these can be set incorrectly during Containerfile
+  # ADD instruction.
+  local path
+  for path in "/etc/systemd/system.conf.d" "/etc/systemd/system/user-.slice.d"; do
+    chown root:root ${path}/*
+    chmod 0644 ${path}/*
+  done
+}
+
+check_vars
+main