Why are ESXi logs stored in non-persistent storage by default?

ESXi hosts that boot from USB or SD cards store logs in a RAM disk by default because these boot media have limited write cycles and storage capacity. This means logs are held in volatile memory and are lost when the host reboots or powers off, which can hinder troubleshooting and compliance requirements.

How do I configure persistent logging on an ESXi host?

You can configure persistent logging by directing the syslog output to a datastore. Use the esxcli command: esxcli system syslog config set --logdir /vmfs/volumes/datastore_name/logs. Alternatively, configure it through the vSphere Client under Host > Configure > System > Advanced System Settings by setting the Syslog.global.logDir parameter.

Will configuring persistent logging affect ESXi performance?

Configuring persistent logging to a local datastore has minimal performance impact. However, if you redirect logs to a shared datastore (like NFS or VMFS on SAN), consider the additional I/O overhead. For best performance, use a local datastore or a dedicated syslog server. The log volume is generally small and should not significantly impact storage performance. When working with ESXi logs non-persistent storage, this step is critical for success.

ESXi Logs Non-Persistent Storage: 5 Essential Fixes

On ESXi host ESX01.company.local, system logs are currently being stored in non-persistent storage. This means that any logs generated when the host is powered off or rebooted will be lost. This can be a problem if you need to troubleshoot issues that occur during those times.

Why This Could Be a Problem

There are several reasons why storing system logs in non-persistent storage could be a problem:

Lost Data: If the host is powered off or rebooted, any logs generated during that time will be lost. This could make it difficult to troubleshoot issues that occur during those times.
Limited Troubleshooting: Without access to historical logs, troubleshooting issues can be more difficult and time-consuming.
Missing Evidence: In some cases, system logs may be required as evidence for legal or compliance purposes. If the logs are not available, it could be difficult to prove what happened.

Using ESXCLI for Persistent Logging Configuration

The esxcli command-line interface offers a powerful way to manage various aspects of ESXi hosts, including configuring system logging. To enable persistent logging and direct logs to a specific datastore, follow these steps:

Use an SSH client to connect to the ESXi host.
Execute the following command to set the log directory:

esxcli system syslog config set --logdir /vmfs/volumes/<datastore_name>/logs

Replace <datastore_name> with the actual name of the datastore where you want to store the logs.

To confirm that the configuration is updated, run the following command:

esxcli system syslog config get

This command should display the new log directory path you specified.

Additional Considerations

Permissions: Ensure that the ESXi host has write permissions to the chosen datastore and directory.
Log Rotation: Configure log rotation to manage the size and number of log files.
Remote Syslog: As an alternative to storing logs on the local datastore, consider sending them to a remote syslog server for centralized management and analysis.

Conclusion

Storing system logs in non-persistent storage on an ESXi host can be a problem. This can lead to lost data, limited troubleshooting capabilities, and missing evidence. Fortunately, there are a number of ways to fix this issue, including enabling persistent logging, using a remote syslog server, and using a third-party logging solution. By implementing one of these solutions, you can ensure that your ESXi logs are properly stored and accessible when needed.