FAQ

Even in regions where E-HPC is supported, cluster creation can fail if the underlying resources are unavailable. The two most common causes:

• No NAS file system available: File Storage NAS (NAS) can't be created in that region, or no NAS file system exists. E-HPC requires NAS to mount shared storage on the cluster.

• ECS instance types unavailable: The region or zone doesn't have the Elastic Compute Service (ECS) instance types needed for your compute nodes, or inventory is exhausted.

Select a different region and try again.

No. Each node runs on an ECS instance, but E-HPC manages the full lifecycle of those instances—batch creation, management system deployment, software pre-installation, and job scheduler configuration. Managing nodes directly in the ECS console bypasses these processes and can cause cluster or node failures, or make cluster resources unavailable.

It depends on whether the node and the ECS instance are in the same virtual private cloud (VPC):

• Same VPC: They communicate directly within the VPC.

• Different VPCs: Connect the VPCs first. Use Cloud Enterprise Network (CEN) or VPC peering to enable communication between private networks.

You may fail to log on to a cluster using Workbench or another Secure Shell (SSH) client for various reasons. Troubleshoot and resolve the issue based on your specific situation.

Work through these checks in order:

1. Verify the username and password are correct.

2. Check that your local network and carrier network are up.

3. Confirm the security group rule for the logon node allows access to port 22 (the default SSH port).

4. Check whether the security group of the node allows access from IP addresses related to the Workbench service. The security group rules vary based on the network type. For more information, see Log on to a Linux instance using Workbench.

5. Run iptables -nvL --line-number on the logon node to check whether a firewall or firewall rules are blocking connections.

If none of these resolve the issue, connect using Virtual Network Computing (VNC) instead. See FAQ about connecting to ECS instances.

Cause: This is a known systemd bug that surfaces when Network Information Service (NIS) is in use. Symptoms include slow SSH logins or node switching, occasional login failures, and an inability to restart sshd with the error Failed to activate service 'org.freedesktop.systemd1': timed out.

Solution:

1. Log in to the node as root.

2. Check /etc/nsswitch.conf to see whether [NOTFOUND=return] is missing from the passwd, shadow, and group entries:

   cat /etc/nsswitch.conf

   If the output looks like the following, proceed to the next step:

   passwd:     files sss nis
   shadow:     files sss nis
   group:      files sss nis

3. (Optional) Upgrade glibc:

   yum update glibc

4. Open /etc/nsswitch.conf and add [NOTFOUND=return] to the passwd, shadow, and group lines:

   vim /etc/nsswitch.conf

   Update the entries to:

   passwd:      files sss nis [NOTFOUND=return]
   shadow:      files sss nis [NOTFOUND=return]
   group:       files sss nis [NOTFOUND=return]

5. Save the file.

No. Auto scaling depends on the job scheduler and domain account service running on the management node. Stopping the management node while auto scaling is active can cause failures.

If you need to shut down or restart the management node, first wait for idle nodes to be released and confirm no jobs are running on compute nodes. Disable auto scaling before shutting down, then re-enable it after the management node restarts.

By default, a Slurm cluster in E-HPC has eight dummy nodes. If the cluster already has five compute nodes, jobs can use up to 13 nodes total. To run jobs that require more nodes, add compute nodes or increase the number of dummy nodes.

To increase the number of dummy nodes:

1. Log in to the cluster as root. See Log on to an E-HPC cluster.

2. Add dummy node files to /opt/slurm/<slurm_version>/nodes. For example, to support 18 nodes with 5 existing compute nodes, add 10 dummy nodes named dummyNode8 through dummyNode17.

   <slurm_version> is the Slurm version installed in your cluster.

3. In /opt/slurm/<slurm_version>/etc/slurm.conf, find PartitionName and add the new dummy nodes. For example:

   PartitionName=comp Nodes=dummynode0,dummynode1,dummynode2,dummynode3,dummynode4,dummynode5,dummynode6,dummynode7,dummynode8,dummynode9,dummynode10,dummynode11,dummynode12,dummynode13,dummynode14,dummynode15,dummynode16,dummynode17,compute000 Default=YES MaxTime=INFINITE State=UP

Select the Slurm version on the 2. Software Configurations page during cluster creation. Unless your workload requires a specific version, use the latest supported version. E-HPC currently supports up to slurm22.

If you want to use Alibaba Cloud services in the Chinese mainland, complete account verification first. Without it, selecting a Chinese mainland region when purchasing services triggers an error on the buy page. For details, see FAQ about account verification of Alibaba Cloud accounts.

Problem description

A compute node in the cluster has an Abnormal status and cannot schedule tasks, as shown in the following figure:

Possible cause

This issue may occur because you enabled the system firewall on the management node. This prevents the ypbind service on the compute nodes from working correctly, which in turn prevents the system from scheduling tasks.

Solution

Disable the system firewall on the control plane node.

1. Log on to the management node as the root user.

2. Run the following command to stop the firewalld service.

   systemctl stop firewalld

3. Run the following command to prevent the firewalld service from starting on boot.

   systemctl disable firewalld

4. Run the following command to check the status of the firewalld service on the management node. Make sure that the service is stopped and does not restart on boot.

   systemctl status firewalld

E-HPC supports the following image types:

• Public images: Images provided by Alibaba Cloud.

• Custom images: Images created from ECS instances or snapshots, or imported from your local machine.

• Shared images: Images shared by other Alibaba Cloud accounts.

• Alibaba Cloud Marketplace images: Images from independent software vendors (ISVs) licensed through Alibaba Cloud Marketplace.

• Community images: Images published on the Alibaba Cloud Community image platform.

When creating or scaling out a cluster, or configuring an auto scaling policy, a custom image won't appear in the list if any of the following apply:

• Your account has no custom image in the current region. See Overview for how to create one.

• The custom image's operating system isn't supported by E-HPC.

• The node's instance type doesn't support the custom image.

• When configuring an auto scaling policy, the image in the global settings and queue settings must match.

Custom images must meet the following requirements. If your image doesn't meet them, creation or scale-out will fail:

• The yum source configuration in the image cannot be modified.

• /home and /opt cannot be mount directories or symbolic links in the image.

• If /etc/fstab contains mount entries for external file systems (such as NFS), the cluster must be able to access those file systems, or they must be in the same VPC. Remove any inaccessible entries from /etc/fstab before creating the cluster.

• The image must retain the group with account group ID 1000.

• The system disk size must be at least as large as the custom image.

E-HPC supports importing CentOS images only. For import steps, see Import an image.

When importing, make sure Check After Import is selected. Without it, the image may not appear in the E-HPC console.

E-HPC clusters use File Storage NAS to share data across compute nodes, so software installed in a shared directory is immediately accessible to all nodes.

Choose the installation location based on who needs access:

• All cluster users: Install to /opt.

• A single cluster user: Install to that user's home directory.

When creating an E-HPC cluster, specify both a mount target and a remote directory for the NAS file system. Example configuration:

ClusterId=ehpc-mrZSoWf****          # Cluster ID
VolumeMountpoint=045324****-m****.cn-hangzhou.nas.aliyuncs.com  # NAS mount target
RemotePath=/                         # Remote directory (NAS root)

To mount specific subdirectories on the cluster:

1. Create subdirectories under the NAS root before mounting:

   /ehpc-mrZSoWf****/opt
   /ehpc-mrZSoWf****/home

2. When creating (or after creating) the cluster, set the remote directory to the appropriate subdirectory. For example:

   /                          # Mounts to /ehpcdata on the cluster
   /ehpc-mrZSoWf****/home     # Mounts to /home on the cluster
   /ehpc-mrZSoWf****/opt      # Mounts to /opt on the cluster

   For full configuration steps, see Create a cluster by using the wizard and Manage storage resources.

Create the mount target and the mount directory before mounting the NAS file system.

The default limit is three clusters per region. To increase the quota, submit a ticketsubmit a ticketsubmit a ticketsubmit a ticket.

An E-HPC cluster supports up to 500 nodes. You can also add up to 500 compute nodes at a time. To increase either limit, submit a ticketsubmit a ticketsubmit a ticket.

Resource Access Management (RAM) provides a service-linked role called AliyunServiceRoleForEHPC for E-HPC. This role lets E-HPC access associated cloud resources—specifically ECS, VPC, and NAS.

If this role isn't attached to your account, complete role authorization before using E-HPC. See Manage a service-linked role.

If a RAM user hasn't been granted the AliyunEHPCReadOnlyAccess permission, the console displays the Switch to RAM for authorization message. Grant AliyunEHPCReadOnlyAccess to the RAM user to restore read access.

To allow a RAM user to create clusters, users, or jobs, grant both AliyunEHPCFullAccess and AliyunNASFullAccess. See Grant permissions to a RAM user.