What is the ESXi shell?

The ESXi shell refers to the command-line interface in VMware’s ESXi hypervisor that allows administrators to configure, troubleshoot, and manage the ESXi host at a low level.

What is the ESXi shell?

Accessing the ESXi Shell

There are a few different ways to access the ESXi shell:

  • Direct console access – Connect a monitor and keyboard directly to the ESXi host.
  • SSH – Connect to the ESXi host using SSH from another machine. ESXi enables SSH access by default.
  • vSphere Console – Connect to the virtual console of the ESXi host using the vSphere web client.

To log into the ESXi shell you’ll need to provide valid administrator credentials for the host.

Using the ESXi Shell

The ESXi shell includes many commands and utilities for managing the host at a low level, including:

  • esxcfg – Configure advanced host settings.
  • esxtop – Monitor host performance and utilization.
  • vim-cmd – Manage vSphere infrastructure like VMs, networking, and storage.
  • vmkfstools – Manage VMFS volumes and datastores.
  • vmkping/vmkneighbord – Troubleshoot networking issues.

The ESXi shell uses a Linux-style environment with features like tab autocompletion to make entering commands easier.

Useful ESXi Shell Commands

Here are some commonly used ESXi shell commands:

  • vim-cmd vmsvc/power.off <vmname> – Power off a virtual machine
  • esxtop – Open an interactive performance monitor
  • esxcfg-mpath -L – List multipath settings
  • esxcli network ip interface list – List VMkernel interfaces
  • vim-cmd hostsvc/firmware/backup_config – Backup host configuration

Tip: Many ESXi shell commands have additional flags and options for more advanced usage. See the manual page for individual commands by adding -h or –help.

Optimizing and Customizing the ESXi Shell

The default ESXi shell works well but can be optimized and customized further:

  • Install PowerCLI – VMware’s PowerCLI adds many powerful scripting capabilities.
  • Increase scrollback buffer – Store more output lines before they get cleared.
  • Custom shell prompts – Make your prompt more informative.
  • Setting aliases – Create shortcut commands.
  • *Use a “.rc” file – Execute commands whenever you start a shell session.

Increasing the Scrollback Buffer

To store more output from commands before it gets cleared:

  1. Enter the ESXi shell and run: esxcfg-advcfg -g /UserVars/ESXiShell/MaxLines
  2. Increase the value to a larger number e.g. 10000
  3. Restart the ESXi shell session and verify the change took effect

Now you can scroll back through thousands of lines of output if needed.

When to Use the ESXi Shell

The ESXi shell gives full low-level control of the hypervisor. Some examples of when it can be useful:

  • Troubleshooting issues when the host is unreachable from the network
  • Testing host configurations before formalizing them
  • Scripting automation tasks through PowerCLI
  • Performing advanced host customizations
  • Debugging performance problems using esxtop
  • Recovering from failures using rescue mode

In many cases though, VMware’s vCenter Server GUI and automation APIs provide an easier way to manage key tasks.

The ESXi shell is best treated as a fallback tool for when more user-friendly options aren’t available. Understanding it can help recover from outages and fine-tune a host.

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Key Takeaway

The ESXi shell provides low-level command-line access to the VMware ESXi hypervisor. It can be used to troubleshoot issues, monitor performance, configure advanced settings, and automate management of an ESXi host.

While powerful, the ESXi shell uses a Linux-style interface that may be unfamiliar to some users. It is often a fallback tool, but learning it helps unlock the full capabilities of ESXi for recovery and customization tasks.

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Conclusion

Accessing the ESXi shell opens up greater control over the hypervisor for troubleshooting and automation. While it has a learning curve, understanding key commands like esxtop, vim-cmd, esxcfg-*, and vmk* allows an administrator to tap into the full power of ESXi.

Combining the shell with utilities like PowerCLI can enable advanced management and monitoring. Treat the shell as one tool among many to master the comprehensive capabilities of VMware’s industry-leading ESXi hypervisor.

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Frequently Asked Questions

Q: How do I enable SSH access to the ESXi shell?
A: SSH access is enabled by default in ESXi. Just connect using any SSH client to the ESXi host’s management IP address.

Q: What permission do I need to access the ESXi shell?
A: You need administrative privileges on the ESXi host, with root access allowing full use of all commands.

Q: Can I automate ESXi shell commands and scripts?
A: Yes, utilities like PowerCLI allow you to easily run ESXi shell commands and scripts for automation.

Q: Is the ESXi shell based on Linux or Windows?
A: The ESXi hypervisor has a Linux kernel at its core, so the shell uses a Linux-style environment.

Q: How do I get help for ESXi shell commands?
A: Append -h or –help to any command to view its manual page and usage information.

Q: Can I permanently customize the ESXi shell?
A: Yes, you can add customizations like aliases, shell prompts, and startup scripts using “.*rc” files.

Q: Does the ESXi shell work the same on the free and paid ESXi versions?
A: Yes, the shell capabilities are identical across free ESXi and commercial vSphere editions.

Q: Is PowerCLI required to use the ESXi shell effectively?
A: No, but PowerCLI adds many additional scripting capabilities for automation.

Q: Can I damage my ESXi host using shell commands?
A: Yes, the shell provides low-level access and some commands can cause issues if used incorrectly.

Q: How can I monitor ESXi host performance from the shell?
A: The esxtop interactive command provides detailed real-time performance graphs and statistics.

Q: Is there tab autocompletion for ESXi shell commands?
A: Yes, pressing tab while typing a command will auto-complete common options and arguments.

Q: Does ESXi’s Direct Console User Interface (DCUI) provide a shell?
A: Yes, the DCUI includes a shell accessible via keyboard attached the ESXi host’s physical console.

Q: What troubleshooting tools are available in the ESXi shell?
A: Key troubleshooting tools are esxtop, esxtoolkit, vmkping, vmkping6, esxcli network, and vim-cmd commands.

Q: How do I connect to the shell through the vSphere Client?
A: Use the console tab to connect to the virtual console of the ESXi host for shell access.

Q: Can I establish persistent shell sessions to avoid reauthentication?
A: Yes, use tools like PowerCLI or SSH to establish long-running authenticated sessions.

Q: Where are logs for ESXi shell activity stored
A: The shell uses the local hostd log which can be accessed at /var/log/hostd.log.

Q: Is there documentation from VMware on common ESXi shell commands?
A: Yes, extensive documentation is available on the VMware Docs site and vSphere Examples Github.

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