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Repurposing a Compute Node as a UAN

This section describes how to repurpose a compute node to be used as a User Access Node (UAN). This reconfiguration is typically done when the processor type of the compute node is not yet available in a UAN server.

Overview

The following steps outline the process of repurposing a compute node to be used as a UAN.

Verify that the System Default Route is set to CHN.
Change the role of the compute node in the Hardware State Manager from Compute to Application and set the subrole to UAN.
Ensure that IP addresses on the CHN exist for the compute nodes in SLS.
Boot the repurposed compute node as a UAN.
Verify the repurposed compute node functions as a UAN.

Prerequisites

There are no changes needed in hardware, network cabling, or UEFI/BIOS/BMC configuration to repurpose a compute node for use as a UAN. However, compute nodes do not have the necessary NICs to support user access over the Customer Access Network (CAN). Additionally, the network configuration of Mountain Cabinets does not support the CAN network. Therefore, repurposing a compute node as a UAN requires the system to be configured to use the Customer High-Speed Network (CHN). The compute nodes must also have a CHN IP address in SLS.

The SLS Networks setting for the SystemDefaultRoute must be CHN
The repurposed compute nodes must have CHN IP addresses in SLS
uan_can_setup must be set to true in the uan-config-management repo

Procedure

Perform the following steps to repurpose a compute node for use as a UAN.

Log in to the master node ncn-m001. All commands in this procedure are run from the master node.
Verify that the system is configured to use the CHN as the System Default Route. If the SystemDefaultRoute is not CHN, the compute nodes may not be repurposed as UAN.
```
ncn-m001# cray sls networks describe BICAN  --format json | jq -r '.ExtraProperties.SystemDefaultRoute'
```
Verify that a CHN IP address exists in SLS for each repurposed compute node. Repeat the following command and replace <XNAME> with the xname of each repurposed compute node. The compute node must have a CHN IP address in SLS or it cannot be repurposed as a UAN. See Add Compute IP addresses to CHN SLS data section of the Cray System Management documentation for information on adding compute nodes to the CHN.
```
ncn-m001# cray sls networks describe CHN | q -r '.ExtraProperties.Subnets[] | select(.FullName == "CHN Bootstrap DHCP Subnet") | .IPReservations[] | select(.Comment == "<XNAME>")'
```
Verify that uan_can_setup: true is set in the uan-config-management CFS repo. See Enabling the Customer Access Network (CAN) or the Customer High Speed Network (CHN) for more information.
Change the role and subrole in HSM of the compute node or nodes being repurposed as UANs to Application and UAN, respectively. Repeat the following command and replace <XNAME> with the xname of each repurposed compute node.
```
ncn-m001# cray hsm state components role update --role Application --sub-role UAN <XNAME>
```
Verify the role and subrole in HSM of the repurposed compute node or nodes have been changed to ‘Application and 'UAN, respectively. Repeat the following command and replace <XNAME> with the xname of each repurposed compute node.
```
ncn-m001# cray hsm state components describe <XNAME>
```
Run the BOS session template used to boot the UAN nodes. See Boot UAN Nodes for more information on booting UAN nodes with BOS. Replace <UAN_SESSIONTEMPLATE> with the name of the BOS session template used to boot the UAN nodes and <XNAME> with the xname of the repurposed compute node.
```
ncn-m001# cray bos session create --template-uuid <UAN_SESSIONTEMPLATE> --operation reboot --limit <XNAME>
```

Verification as a UAN

After the repurposed compute node is booted as a UAN, the following steps will verify it is configured as a UAN. These steps may vary dependent upon how the site has configured the UAN nodes.

Basic UAN Configuration Checks

Verify that the repurposed compute node has finished the configuration phase. This command must return configured.
```
ncn-m001# cray cfs components describe <XNAME> --format json | jq -r .configurationStatus
```
Login to the repurposed compute node from the master node ncn-m001 as the root user.
Verify that the hsn0 interface has the CHN IP address assigned to it in SLS.
```
uan# ip a | grep hsn0
```
Verify that the default route is through hsn0
```
uan# ip r | grep default
```
Verify that all site UAN filesystems are mounted.

Common UAN Configuration Checks

If LDAP is used for user authentication, verify that the LDAP service is reachable.
```
uan# ping <ldap_service_ip>
```
If Slurm is used, test sinfo and srun commands. This example srun command should return the hostname of four compute nodes.
```
uan# sinfo

uan# srun -N4 hostname
```

Login to the repurposed compute node as an authorized non-root user from any host that should have UAN access.
If Slurm is used, test sinfo and srun commands. This example srun command should return the hostname of four compute nodes.
```
uan# sinfo

uan# srun -N4 hostname
```