PowerScale: OneFS Configuring sysctl changes to persist through node and cluster reboots and upgrades

This article provides procedures for testing sysctl configuration changes and editing the sysctl.conf file across the cluster. 
This allows sysctl changes to persist through node, and cluster reboots and through OneFS upgrades.

Summary

In OneFS, various kernel parameters can be changed using sysctl commands. Some of these parameters are specific to OneFS and others are generic to the Berkeley Software Distribution (BSD) operating system.

Remember to ALWAYS check defaults before modifying sysctl's. 
If checking a sysctl that has never been modified with isi_sysctl_cluster, it shows a value of #None since the value was never modified. 
This is due to the override file never being updated of a change, which isi_sysctl_cluster is pulling the information from. 
In these cases sysctl <sysctl name> or isi_for_array -s <sysctl name> should be ran to see the unmodified defaults prior to any modifications. 

 

Procedures

Test a sysctl configuration change or make a configuration change that is not persistent.

Apply a sysctl configuration change to a node in the cluster:

1. Open an SSH connection on any node in the cluster and connect using the "root" account.
2. Run the following command to get the current value of the sysctl, where <sysctl_name> is the parameter being configured:
    

   sysctl <sysctl_name>

   
   
    
3. Run the following command, where <sysctl_name> is the parameter to be configured, and, when applicable, <value> is the value to assign to the parameter:
    

   sysctl <sysctl_name>=<value>

4. Apply a sysctl configuration change to the cluster.
5. Open an SSH connection on any node in the cluster and connect using the "root" account.
6. Run the following command where <sysctl_name> is the parameter to add or change, and when applicable <value> is the value to assign to the parameter:
    

   isi_for_array -s sysctl <sysctl_name>=<value>

   
    

Make a sysctl configuration change persistent.

Add to or change the wanted parameter in the sysctl.conf file:

1. Open an SSH connection on any node in the cluster and connect using the "root" account.
    
2. Run the following command to back up the /etc/mcp/override/sysctl.conf file:
    

   touch /etc/mcp/override/sysctl.conf && cp /etc/mcp/override/sysctl.conf /etc/mcp/override/sysctl.conf.bku1

   
    
3. Run the following command, where <sysctl_name> is the parameter to add or change and <value> is the value to assign to the parameter:
    

   isi_sysctl_cluster <sysctl_name>=<value>

   
   
   The following output displays:
    

   Value set successfully

   
    
4. Verify that the change was successfully added to the /etc/mcp/override/sysctl.conf file by running the following command:
    

   cat /etc/mcp/override/sysctl.conf

   
   
   Output similar to the following displays:
    

   <sysctl_name>=<value> #added by script

5. Revert changes made to the sysctl.conf file.

These steps revert the sysctl.conf file to the backup version previously created in the previous section.

1. Open an SSH connection on any node in the cluster and connect using the "root" account.
2. Run the following command to copy and then rename the original backup of the sysctl.conf file:
    

   cp /etc/mcp/override/sysctl.conf.bku1 /etc/mcp/override/sysctl.conf