ndctl (with examples)

1: Create an ‘fsdax’ mode namespace

ndctl create-namespace --mode=fsdax

Motivation: This command allows the creation of a new namespace with ‘fsdax’ mode. ‘fsdax’ mode allows applications direct access to persistent memory as a file system.

Explanation: This command creates a new namespace with the specified mode. The --mode=fsdax argument sets the mode of the namespace to ‘fsdax’.

Example Output:

Created nmem0 namespace

2: Change the mode of a namespace to ‘raw’

ndctl create-namespace --reconfigure=namespaceX.Y --mode=raw

Motivation: This command allows changing the mode of an existing namespace to ‘raw’. ‘raw’ mode provides direct access to the underlying memory without any file system layer.

Explanation: This command changes the mode of an existing namespace to ‘raw’. The --reconfigure=namespaceX.Y argument specifies the namespace to be reconfigured, and --mode=raw sets the new mode.

Example Output:

Reconfigured namespaceX.Y with 'raw' mode

3: Check a sector mode namespace for consistency and repair if needed

ndctl check-namespace --repair namespaceX.Y

Motivation: This command helps ensure the consistency of a sector mode namespace and repairs any inconsistencies if found. Checking and repairing namespaces can prevent data corruption and ensure data integrity.

Explanation: This command checks the specified namespace for consistency. The --repair argument indicates that any inconsistencies should be repaired.

Example Output:

Namespace namespaceX.Y is consistent and does not require repair

4: List all namespaces, regions, and buses (including disabled ones)

ndctl list --namespaces --regions --buses --idle

Motivation: This command provides a comprehensive overview of all namespaces, regions, and buses. It includes both enabled and disabled resources, allowing for a complete understanding of the available devices.

Explanation: This command lists all namespaces, regions, buses, and their respective state. The --namespaces, --regions, --buses, and --idle arguments are used to include all relevant information.

Example Output:

Namespaces:
  Namespace: /dev/pmem0
  [Other namespaces listed here]

Regions:
  Region: region0
  Device: /dev/nmem0
  [Other regions listed here]

Buses:
  Bus: ACPI.NFIT:0
  [Other buses listed here]

5: List a specific namespace and include lots of additional information

ndctl list -vvv --namespace=namespaceX.Y

Motivation: This command provides detailed information about a specific namespace. It can be useful for troubleshooting or gathering extensive information about a particular resource.

Explanation: This command lists the specified namespace and includes verbose information. The -vvv argument increases the level of verbosity, providing additional details.

Example Output:

Namespace: namespaceX.Y
    mode: fsdax
    size: 1.0 GB
    alignment: 4.0 KB
    sector_size: 512 Bytes
    [Other attributes and details listed here]

6: Run a monitor to watch for SMART health events for NVDIMMs on the ‘ACPI.NFIT’ bus

ndctl monitor --bus=ACPI.NFIT

Motivation: This command enables monitoring for SMART health events on NVDIMMs connected to the ‘ACPI.NFIT’ bus. Monitoring helps detect potential issues and allows for proactive maintenance and troubleshooting.

Explanation: This command starts a monitor for SMART health events on the specified bus. The --bus=ACPI.NFIT argument indicates the target bus for monitoring.

Example Output:

Monitoring SMART health events on bus ACPI.NFIT...
[SMART health events are displayed here in real-time]

7: Remove a namespace (when applicable) or reset it to an initial state

ndctl destroy-namespace --force namespaceX.Y

Motivation: This command allows removal or reset of a namespace. Removing a namespace frees up resources, while resetting it to an initial state can help resolve persistent issues.

Explanation: This command destroys the specified namespace. The --force argument ensures that the operation is carried out even if the namespace is in use.

Example Output:

Namespace namespaceX.Y has been removed/reset successfully

Conclusion

The ndctl command is a versatile utility for managing Non-Volatile DIMMs. It provides various functionalities, including creating and reconfiguring namespaces, checking and repairing namespace consistency, listing resources, monitoring health events, and removing/resetting namespaces. The examples provided demonstrate the different use cases of the ndctl command and illustrate how it can be used to effectively manage Non-Volatile DIMMs.