[Update May 2024]
The information below is quite dated. It's pretty easy to patch ESXi via the CLI these days. Head over to the VMware ESXi Patch Tracker. There you can find all the updates available for ESXi 7 and 8 and the corresponding esxcli commands to patch your host manually.
If you have purchased vSphere you can use Update Manager to Scan, Stage and Remediate patches to the machines running ESXi in your cluster. If you don'thave vSphere you can always update ESXi manually. The instructions below give you one method to patch manually.
1. Determine which version of ESXi 5.X you are running. To do this - connect to the ESXi machine with the vSphere client typically asroot. Help / About will show you your vSphere Client and VMware ESXi version and build numbers.
2. Then proceed to the Download Patches page on VMware's website. You will need to log in to the site to download patches. Now complete a search for ESXi (Embedded and Installable) for the appropriate version of ESXi5.X. This will give you a list of patches as per the screenshots below. You now need to work out which patches you need to download. These can range in size from 100MB to 700MB.
3. Once the patches have been downloaded, ensure you have downloaded and installed the VMware vSphere 5.5 CLI (vCLI).
4. Now place the ESXi machine to be patched in maintenance mode.
5. Upload the patch zip files (depots) to the local datastore of the ESXi box.
6. Determine the complete path to the datastore. In the vSphere client, this can be obtained by clicking on the Configuration tab, Storage option and selecting the Local Disk. In this case the datastore path is /vmfs/volumes/datastore1.
7. Next, open a command prompt and change directory to the vCLI bin directory, which should be C:\Program Files (x86)\VMware\VMware vSphere CLI\bin.
8. Now ensure you can read uploaded depots using the following vCLI command. You will be prompted for the root password before executing the command:
esxcli --server=<servername> --username=root software sources vib list --depot=/vmfs/volumes/datastore1/ESXi550-201510001.zip
You should see output similar to the following:
9. Now apply the depot using the following command. You may have to reboot the ESXi box after the depot has been applied before applying the next depot.
esxcli --server=<servername> --username=root software vib update --depot=/vmfs/volumes/datastore1/ESXi510-201510001.zip
You should see output similar to the following:
10. ... and that's it - after the ESXi box reboots it will be running the version you just patched up to. Remember to delete the patches from the local datastore as they are no longer required. Also take the ESXi box out of maintenance mode. More information can also be found here.
Originally published 9 May 2016.