Today i found a strange behaviour on a freshly deployed Powerpath vAPP.

Because the customer DNS server wasn’t ready at the time of the deployment, i had to use the local “/etc/hosts” file.

I opened the /etc/hosts file with my editor of choice and added the lines for all ESXi servers + the vCenter itself.
The reason for that is that if the Powerpath vAPP can’t resolve the names of the ESXi servers that have to be licensed, the ESXi servers show as unlicensed in the GUI.

vapp:~ # vi /etc/hosts
127.0.0.1     localhost.localdom      localhost      
localhost.localdom      localhost
#ESXi and vCenter
10.77.77.20        vcenter vcenter.localdom.local
10.77.77.25         esx001  esx001.localdom.local
10.77.77.26         esx002  esx002.localdom.local
10.77.77.27         esx003  esx003.localdom.local
10.77.77.28         esx004  esx004.localdom.local
10.77.77.29         esx005  esx005.localdom.local
10.77.77.30         esx006  esx006.localdom.local

After rebooting the vAPP appliance, the “/etc/hosts” file is automically reset to default

vapp:~ # vi /etc/hosts
 127.0.0.1     localhost.localdom      localhost
 localhost.localdom      localhost

Now this happens because the Powerpath vAPP is deployed as a Virtual Appliance, and this has an in‐guest management component called Virtual Appliance Management Infrastructure (VAMI).

VAMI places a lot of scripts in the vAPP located in the following directory:

#/opt/vmware/etc/isv

The script that is responsible for rewriting the hosts file is called

#subsequentboot

To prevent VAMI from resetting the host file:

– Open vi with the file “subsequentboot”

localhost:/ # vi /opt/vmware/etc/isv/subsequentboot

– Comment the following 2 lines in line 23/24:

#echo "127.0.0.1     localhost.localdom      localhost"  >       /etc/hosts
#echo "$HOSTADDR     $FQDNADDR      $SHORTHNAME"         >>      /etc/hosts

Edit the “/etc/hosts” file again and reboot…
Voilá…”/etc/hosts” file should still have all the entries that you put in