diff --git a/docs/dictionary/en-custom.txt b/docs/dictionary/en-custom.txt
index 67aae5cf2..b6c483033 100644
--- a/docs/dictionary/en-custom.txt
+++ b/docs/dictionary/en-custom.txt
@@ -554,6 +554,7 @@ rnkhwaejdughvnuzsdz
 ro
 rolename
 rootdevicehints
+rootfs
 rpms
 rpmss
 rsa
@@ -637,6 +638,7 @@ undercloud
 unicast
 unittest
 unmanaged
+unallocated
 uoyt
 uri
 usermod
diff --git a/roles/bm_sno/README.md b/roles/bm_sno/README.md
index 259c7214f..1b2795745 100644
--- a/roles/bm_sno/README.md
+++ b/roles/bm_sno/README.md
@@ -62,6 +62,7 @@ provision IP via `/etc/hosts` entries managed by the role.
 | `cifmw_bm_agent_core_password` | str | — | Set a `core` user password post-install via MachineConfig |
 | `cifmw_bm_agent_live_debug` | bool | `false` | Patch the agent ISO with password, autologin, and systemd debug shell on `tty6` for discovery-phase console access (requires `cifmw_bm_agent_core_password`) |
 | `cifmw_bm_agent_disabled_ifaces` | list | `[]` | Extra NIC names to disable IPv4/IPv6 on during agent-based install. Prevents overlapping-subnet validation failures when multiple NICs share a native VLAN (e.g. `[eno2]`). The interfaces stay link-up but get no IP address; post-install NNCP configures them. |
+| `cifmw_bm_agent_lvms_partition` | dict | `{}` | When set, creates an Ignition partition at install time to cap CoreOS rootfs growth and leave unallocated space for the LVMS StorageClass. Keys: `device` (required, e.g. `/dev/nvme0n1`), `rootfs_mib` (default `150000`), `size_mib` (default `0` = rest of disk), `label` (default `lvmstorage`). See [LVMS partition](#lvms-partition). |
 
 ## Secrets management
 
@@ -119,17 +120,18 @@ If the binary already exists in the working directory it is reused.
 2. Ensure `GenericUsbBoot` is enabled in BIOS (auto-enable with power cycle if allowed)
 3. Power off the host
 4. Generate SSH keys, template `install-config.yaml` and `agent-config.yaml`
-5. Acquire `openshift-install` binary (see above) and run `openshift-install agent create image` to build the agent ISO
-6. Optionally patch the ISO for discovery-phase console access
-7. Serve the ISO via a root podman httpd container (rootless podman cannot use privileged ports)
-8. Eject any existing VirtualMedia, then insert the agent ISO
-9. Discover the Virtual Optical Drive UEFI path and set a one-time boot override
-10. Power on the host
-11. Verify BIOS `GenericUsbBoot` is enabled after POST
-12. Add `/etc/hosts` entries for `api`/`api-int` and `*.apps` domains
-13. Wait for bootstrap and install to complete
-14. Copy kubeconfig and kubeadmin-password to the dev-scripts-compatible auth directory
-15. Eject VirtualMedia and stop the HTTP server
+5. Optionally generate an LVMS partition MachineConfig into `openshift/` manifests
+6. Acquire `openshift-install` binary (see above) and run `openshift-install agent create image` to build the agent ISO
+7. Optionally patch the ISO for discovery-phase console access
+8. Serve the ISO via a root podman httpd container (rootless podman cannot use privileged ports)
+9. Eject any existing VirtualMedia, then insert the agent ISO
+10. Discover the Virtual Optical Drive UEFI path and set a one-time boot override
+11. Power on the host
+12. Verify BIOS `GenericUsbBoot` is enabled after POST
+13. Add `/etc/hosts` entries for `api`/`api-int` and `*.apps` domains
+14. Wait for bootstrap and install to complete
+15. Copy kubeconfig and kubeadmin-password to the dev-scripts-compatible auth directory
+16. Eject VirtualMedia and stop the HTTP server
 
 ## Molecule tests
 
@@ -267,6 +269,46 @@ cifmw_bm_agent_core_password: changeme
 cifmw_bm_agent_live_debug: true
 ```
 
+## LVMS partition
+
+By default CoreOS expands its rootfs partition to fill the entire disk
+at first boot. To reserve space for the LVMS (Logical Volume Manager
+Storage) StorageClass, set `cifmw_bm_agent_lvms_partition` with at
+least the `device` key. The role injects a MachineConfig manifest into
+the agent ISO that creates a labeled partition via Ignition — before
+`growfs` runs — so CoreOS rootfs stops at `rootfs_mib` and the
+remainder is available for LVMS.
+
+```yaml
+cifmw_bm_agent_lvms_partition:
+  device: /dev/disk/by-path/pci-0000:65:00.0-scsi-0:3:111:0
+  rootfs_mib: 150000   # ~150 GB for CoreOS (minimum 25000)
+  size_mib: 0          # 0 = rest of disk
+  label: lvmstorage    # partition label
+```
+
+After OCP is installed, create an `LVMCluster` CR that targets the
+partition by label:
+
+```yaml
+apiVersion: lvm.topolvm.io/v1alpha1
+kind: LVMCluster
+metadata:
+  name: lvmcluster
+  namespace: openshift-storage
+spec:
+  storage:
+    deviceClasses:
+      - name: lvmstorage
+        deviceSelector:
+          paths:
+            - /dev/disk/by-partlabel/lvmstorage
+        thinPoolConfig:
+          name: thin-pool
+          overprovisionRatio: 10
+          sizePercent: 90
+```
+
 ## References
 
 * [ci-framework reproducer documentation](https://ci-framework.readthedocs.io/en/latest/roles/reproducer.html)
diff --git a/roles/bm_sno/defaults/main.yml b/roles/bm_sno/defaults/main.yml
index 69d846b00..d0fd39cf4 100644
--- a/roles/bm_sno/defaults/main.yml
+++ b/roles/bm_sno/defaults/main.yml
@@ -7,3 +7,14 @@ cifmw_bm_agent_live_debug: false
 cifmw_bm_agent_vmedia_uefi_path: ""
 cifmw_bm_agent_enable_usb_boot: true
 cifmw_bm_agent_disabled_ifaces: []
+
+# LVMS partition: restrict CoreOS rootfs growth and leave
+# unallocated space for the LVMS StorageClass.
+# Set cifmw_bm_agent_lvms_partition to enable.
+# Example:
+#   cifmw_bm_agent_lvms_partition:
+#     device: /dev/disk/by-path/pci-0000:65:00.0-scsi-0:3:111:0
+#     rootfs_mib: 150000    # rootfs capped at ~150 GB
+#     size_mib: 0           # 0 = rest of disk
+#     label: lvmstorage
+cifmw_bm_agent_lvms_partition: {}
diff --git a/roles/bm_sno/tasks/main.yml b/roles/bm_sno/tasks/main.yml
index 02958f470..8c472eb92 100644
--- a/roles/bm_sno/tasks/main.yml
+++ b/roles/bm_sno/tasks/main.yml
@@ -219,6 +219,34 @@
     regexp: '^pullSecret:'
     line: "pullSecret: '<REDACTED>'"
 
+- name: Create LVMS partition MachineConfig manifest
+  when: cifmw_bm_agent_lvms_partition | default({}) | length > 0
+  block:
+    - name: Validate LVMS partition device is set
+      ansible.builtin.assert:
+        that:
+          - cifmw_bm_agent_lvms_partition.device is defined
+          - cifmw_bm_agent_lvms_partition.device | length > 0
+          - (cifmw_bm_agent_lvms_partition.rootfs_mib | default(150000) | int) >= 25000
+        fail_msg: >-
+          cifmw_bm_agent_lvms_partition.device must be set
+          (e.g. /dev/nvme0n1, /dev/disk/by-path/...), and
+          its size must be at least 25000 MB.
+
+    - name: Create openshift manifests directory
+      ansible.builtin.file:
+        path: "{{ _work_dir }}/openshift"
+        state: directory
+        mode: "0755"
+
+    - name: Template LVMS partition MachineConfig
+      vars:
+        _lvms: "{{ cifmw_bm_agent_lvms_partition }}"
+      ansible.builtin.template:
+        src: lvms_partition_machineconfig.yaml.j2
+        dest: "{{ _work_dir }}/openshift/98-lvms-partition.yaml"
+        mode: "0644"
+
 - name: Ensure nmstatectl is available for agent-config networkConfig validation
   become: true
   ansible.builtin.package:
diff --git a/roles/bm_sno/templates/lvms_partition_machineconfig.yaml.j2 b/roles/bm_sno/templates/lvms_partition_machineconfig.yaml.j2
new file mode 100644
index 000000000..aab10e796
--- /dev/null
+++ b/roles/bm_sno/templates/lvms_partition_machineconfig.yaml.j2
@@ -0,0 +1,18 @@
+---
+apiVersion: machineconfiguration.openshift.io/v1
+kind: MachineConfig
+metadata:
+  labels:
+    machineconfiguration.openshift.io/role: master
+  name: 98-lvms-partition
+spec:
+  config:
+    ignition:
+      version: 3.4.0
+    storage:
+      disks:
+        - device: "{{ _lvms.device }}"
+          partitions:
+            - label: "{{ _lvms.label | default('lvmstorage') }}"
+              startMiB: {{ _lvms.rootfs_mib | default(150000) | int }}
+              sizeMiB: {{ _lvms.size_mib | default(0) | int }}