Enable SSH or ESXi Shell on the ESXI Host
Method 1: Without the vSphere Client
DRAC into the ESXI Server and press f2 and enter your credentials
Arrow down to troubleshooting options and press enter, choose to enable either the EXSi shell or SSH or both.
To access the ESXi shell press F1, to return to management press alt F2
Method 2: Using vSphere Client
Log into vSphere and click the host you wish to update. Then select the configuration tab
On the left hand side under software click Security Profile then click Properties in the top right hand corner
Choose SSH and start the service and optionally set to start with the host if you wish to leave it enabled
Check Version and Patch Level
Log into SSH or ESXI shell and run the following command
The following link contains a guide to correlate patch numbers to : http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=1014508
To obtain patches for ESXi visit the following link to download the patches: https://my.vmware.com/group/vmware/patch#search
Upload Patches To Datastore
Create a directory on the datastore called patches and upload the zip files you downloaded to this directory.
Evacuate the VM host of any running VMs and place the host in maintenance mode
Once you have completed the step above access the ESXI CLI from either DRAC or SSH and type the following command
Depending on the update you may need to use install in the syntax instead of update
Reboot the host to complete patch installation once the CLI states install was successful.