Drop support for RHEL 7 / CentOS 7 (#11246)

* Simplify docker systemd unit

systemd handles missing unit by ignoring the dependency so we don't need
to template them.

* Remove RHEL 7/CentOS 7 support

- remove ref in kubespray roles
- move CI from centos 7 to 8
- remove docs related to centos7

* Remove container-storage-setup

Only used for RHEL 7 and CentOS 7

docs/CNI/calico.md

@@ -424,7 +424,7 @@ calico_wireguard_enabled: true
 
 The following OSes will require enabling the EPEL repo in order to bring in wireguard tools:
 
-* CentOS 7 & 8
+* CentOS 8
 * AlmaLinux 8
 * Rocky Linux 8
 * Amazon Linux 2

docs/CRI/docker.md

@@ -16,14 +16,6 @@ Enabling the `overlay2` graph driver:
 docker_storage_options: -s overlay2
 ```
 
-Enabling `docker_container_storage_setup`, it will configure devicemapper driver on Centos7 or RedHat7.
-Deployers must be define a disk path for `docker_container_storage_setup_devs`, otherwise docker-storage-setup will be executed incorrectly.
-
-```yaml
-docker_container_storage_setup: true
-docker_container_storage_setup_devs: /dev/vdb
-```
-
 Changing the Docker cgroup driver (native.cgroupdriver); valid options are `systemd` or `cgroupfs`, default is `systemd`:
 
 ```yaml

docs/developers/ci.md

@@ -8,7 +8,7 @@ To generate this Matrix run `./tests/scripts/md-table/main.py`
 |---| --- | --- | --- | --- | --- | --- | --- | --- |
 almalinux8 |  :white_check_mark: | :x: | :x: | :x: | :white_check_mark: | :x: | :x: | :x: |
 amazon |  :white_check_mark: | :x: | :x: | :x: | :x: | :x: | :x: | :x: |
-centos7 |  :white_check_mark: | :x: | :x: | :white_check_mark: | :x: | :white_check_mark: | :x: | :white_check_mark: |
+centos8 |  :white_check_mark: | :x: | :x: | :white_check_mark: | :x: | :white_check_mark: | :x: | :white_check_mark: |
 debian11 |  :white_check_mark: | :x: | :white_check_mark: | :x: | :x: | :x: | :white_check_mark: | :x: |
 debian12 |  :white_check_mark: | :white_check_mark: | :white_check_mark: | :x: | :x: | :x: | :x: | :x: |
 fedora37 |  :white_check_mark: | :x: | :x: | :x: | :x: | :white_check_mark: | :x: | :x: |
@@ -26,7 +26,7 @@ ubuntu24 |  :white_check_mark: | :x: | :x: | :x: | :x: | :x: | :x: | :x: |
 |---| --- | --- | --- | --- | --- | --- | --- | --- |
 almalinux8 |  :white_check_mark: | :x: | :x: | :x: | :x: | :x: | :x: | :x: |
 amazon |  :x: | :x: | :x: | :x: | :x: | :x: | :x: | :x: |
-centos7 |  :x: | :x: | :x: | :x: | :x: | :x: | :x: | :x: |
+centos8 |  :x: | :x: | :x: | :x: | :x: | :x: | :x: | :x: |
 debian11 |  :x: | :x: | :x: | :x: | :x: | :x: | :x: | :x: |
 debian12 |  :x: | :x: | :x: | :x: | :x: | :x: | :x: | :x: |
 fedora37 |  :white_check_mark: | :x: | :x: | :x: | :x: | :x: | :x: | :x: |
@@ -44,7 +44,7 @@ ubuntu24 |  :x: | :x: | :x: | :x: | :x: | :x: | :x: | :x: |
 |---| --- | --- | --- | --- | --- | --- | --- | --- |
 almalinux8 |  :white_check_mark: | :x: | :x: | :x: | :x: | :x: | :x: | :x: |
 amazon |  :x: | :x: | :x: | :x: | :x: | :x: | :x: | :x: |
-centos7 |  :white_check_mark: | :x: | :x: | :x: | :x: | :x: | :x: | :x: |
+centos8 |  :white_check_mark: | :x: | :x: | :x: | :x: | :x: | :x: | :x: |
 debian11 |  :white_check_mark: | :x: | :x: | :x: | :x: | :x: | :x: | :x: |
 debian12 |  :white_check_mark: | :x: | :x: | :x: | :x: | :x: | :x: | :x: |
 fedora37 |  :x: | :x: | :x: | :x: | :x: | :x: | :x: | :x: |

docs/developers/vagrant.md

@@ -80,7 +80,7 @@ cat << EOF > vagrant/config.rb
 \$instance_name_prefix = "kub"
 \$vm_cpus = 1
 \$num_instances = 3
-\$os = "centos-bento"
+\$os = "centos8-bento"
 \$subnet = "10.0.20"
 \$network_plugin = "flannel"
 \$inventory = "$INV"

docs/operating_systems/centos.md

@@ -1,10 +1,5 @@
 # CentOS and derivatives
 
-## CentOS 7
-
-The maximum python version officially supported in CentOS is 3.6. Ansible as of version 5 (ansible core 2.12.x) increased their python requirement to python 3.8 and above.
-Kubespray supports multiple ansible versions but only the default (5.x) gets wide testing coverage. If your deployment host is CentOS 7 it is recommended to use one of the earlier versions still supported.
-
 ## CentOS 8
 
 If you have containers that are using iptables in the host network namespace (`hostNetwork=true`),