Host Not Responding Error with VMware ESX, vSphere in vCenter

引国外一哥们发的解决方法，貌似是ESX 4.X的方法:

Virtualcenter looses connectivity to an ESX or vSphere host, and all of the virtual machines that are running on the host show as ‘disconnected’. You will also see that the host has ‘not responding’ in brackets next to it’s name.

This one is very simple to fix, as it is usually caused by the host agent service (mgmt-vmware) failing due to a dead process.

First, try and restart the mgmt-vmware service:

# service mgmt-vmware restart

If you find this is hanging when trying to restart the host agent, then you’ll need to kill off the process causing the issue. Open another console session and do the following:

# ps -ef | grep hostd

This will output a list of processes using hostd similar to the following:

root 23955 1 0 10:42 pts/1 00:00:00 /bin/sh /usr/bin/vmware-watchdog -s hostd -u 60 -q 5 -c /usr/sbin/vmware-hostd-support /usr/sbin/vmware-hostd -u
root 23961 23955 4 10:42 ? 00:00:15 /usr/lib/vmware/hostd/vmware-hostd /etc/vmware/hostd/config.xml -u
root 24211 23422 0 10:48 pts/1 00:00:00 grep hostd

If you look at the output carefully you’ll see that the first process is using the vmware-watchdog, this is fine, but the second line is using hostd (config.xml -u). This is the culprit, so lets kill the process. By the way, your virtual machines will continue to run so don’t worry about that.

# kill -9 23961

You’ll now find that the hostd service will start and after a few seconds your host and virtual machines will become available again in vCenter.

官方给出的重启management-agent的方式：

Restart Management agents in ESXi Using Direct Console User Interface (DCUI):

1. Connect to the console of your ESXi host.
2. Press F2 to customize the system.
3. Log in as root.
4. Use the Up/Down arrows to navigate to Troubleshooting Options > Restart Management Agents.
5. Press Enter.
6. Press F11 to restart the services.
7. When the service restarts, press Enter.
8. Press Esc to log out.

Restart Management agents in ESXi Using ESXi Shell or Secure Shell (SSH):

1. Log in to ESXi Shell or SSH as root.
   
   For Enabling ESXi Shell or SSH, see .
   
   
2. Restart the ESXi host daemon and vCenter Agent services using these commands:
   
   /etc/init.d/hostd restart
   
   /etc/init.d/vpxa restart
   

Note: In ESXi 4.x, run this command to restart the vpxa agent:

service vmware-vpxa restart

Alternatively:

 

• To reset the management network on a specific VMkernel interface, by default vmk0, run the command:
  
  esxcli network ip interface set -e false -i vmk0; esxcli network ip interface set -e true -i vmk0
  
  Note: Using a semicolon (;) between the two commands ensures the VMkernel interface is disabled and then re-enabled in succession. If the management interface is not running on vmk0, change the above command according to the VMkernel interface used. 
  
  
• To restart all management agents on the host, run the command:
  
  services.sh restart

别的英文论坛提到重启magement-agent相关服务：

restarting management agents ,On SSH, run these
/etc/init.d/hostd restart
/etc/init.d/vpxa restart

restart the Network Management Agents
/sbin/services.sh restart

问题的根源正是Exsi5.5和下载的vCenter Server Web Client 5.5的小版本不兼容导致的，解决方法请参考博文『vCenter Server连接Exsi主机一段时间后提示Not responding』