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You also might experience a connection problem to the host; you cannot connect directly to the ESXi host or manage it under vCenter Server. As such, restarting the agents will most likely solve the problem. You could possibly do a full reboot, but this requires shutting down all virtual machines (VMs) or moving them to another host.
Fortunately, it is also possible to restart certain services on a host without affecting the VMs running on it. Here are several questions users might ask when this situation occurs.
Which agents need a restart and what's their role? ^
The management agents synchronize VMware components and let you access the ESXi host through the vSphere Client or vCenter Server.
They are included and installed by default when installing ESXi. You might need to restart the management agents if remote access is interrupted depending on whether your ESXi host is managed by vCenter or is a standalone ESXi host (without vCenter management).
The hostd daemon or service runs on every ESXi host and performs major tasks like VM power on and power off. But when an ESXi host joins a vCenter Server, it activates a vpxa agent and talks to a vpxd service that runs in vCenter Server.
Will restarting management agents affect my VMs? ^
No, but it might affect any tasks that may be running on the ESXi host at the time of the restart. But there are no worries for VMs. I'd simply make sure that no backup jobs are running and as such, no snapshots are currently taken.
Also, the management service IP connectivity will drop during a restart of the management agents on the ESXi hosts.
Steps to restart VMware ESXi agents ^
There are two ways of restarting the agents. You can use the direct console user interface (DCUI) or you can do it via a remote Secure Shell (SSH) session.
Direct console user interface (DCUI)
You can use the DCUI if you are in the server room and have a screen attached to your server, or you can do it remotely via Dell Remote Access Controller (DRAC), Intelligent Platform Management Interface (IPMI), or another remote system.
Note: You can also access the DCUI via SSH session by simply typing "dcui" after logging in as root user. In the lab we use the PuTTY SSH client for this job.
- Connect to the console of the ESXi host.
- Press F2 to customize the host and log in as root.
- Go to Troubleshooting Options and choose Restart Management Agents.
The second option is to use an SSH client, connect remotely to your host, and use a command-line code.
/etc/init.d/hostd restart/etc/init.d/vpxa restart
You'll get this output:
Note: Don't forget that before you SSH into ESXi, you need to enable the ESXi shell or SSH.
To do so, you have to connect to your ESXi host via a web browser. Then select the host and go to Actions. From there you can start the ESXi shell and SSH service.
If you want to check which services are running, use this command:
You'll get a view of all services. There are quite of few of them, and you don't really need to know them all—just a couple.
Some of these services are off by default as they only start when you activate certain cluster features, such as VMware virtual storage area network (vSAN).
Final words ^
VMware vSphere management sometimes requires you to administer the solution via command-line interface (CLI). Some admins do not really like this, but after memorizing the first few commands, the curiosity usually picks up, and you try to explore more and more. You can troubleshoot, monitor, or manage ESXi or vSphere from the command line.
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Another issue you might encounter with ESXi agents is that sometimes the performance data collection between the ESXi server and your vCenter is not working properly. Or some performance data might be available, but no recent data is available. This usually means something broke and isn't working. If performance data isn't available, usually you can fix this problem by restarting the VMware management agents too.