A while ago, I talked about what unsupported means. In this post, I will talk about how performing an unsupported change can negatively impact your application — in this case Log Insight.
Virtual Appliances and Supported Changes
A common question for Virtual Appliances (VAs) is what is supported? The answer for VMware VAs can be found here. In short, VMware support may ask that non-standard configurations be removed prior to providing help. This means it is not recommended to make changes to the VA. Such changes may or may not be supported and it may be necessary to reproduce the problem under standard configuration.
Network Configuration in Log Insight
As I hope you know, the ONLY supported way to change networking configuration on Log Insight is through OVF properties. Log Insight does not provide a GUI option to change network settings and while Log Insight ships as a virtual appliance, making networking changes from the CLI is NOT supported.
Changing Network Settings via the CLI
Given that Log Insight ships as a VA, VMware is responsible for the Log Insight software as well as the VA. This results in user changes to the VA not being recommended. For most products, such as Log Insight, while changes via the CLI are unsupported they are not prevented. Note that some VAs, such as NSX, prevent a variety of changes from the CLI. Each approach has its pros and its cons.
The importance /etc/hosts on Log Insight
Like most Linux systems, Log Insight relies on information contained within /etc/hosts. As such, it is critical that the information within the file be correct. As long as you rely on OVF properties, this file will be configured properly. Unfortunately, in a variety of environments I have seen this file incorrectly configured, which indicates an unsupported change to the VA. For example, this is a common configuration I see:
# cat /etc/hosts 192.168.1.25 li
Do you see the problem? The issue is that “localhost” is not resolvable. This is known to cause all sorts of problems on Linux. Another common configuration I see is:
# cat /etc/hosts 192.168.1.25 li localhost 127.0.0.1 localhost.localdom localhost localhost ::1 localhost.localdom localhost localhost ip6-localhost ip6-loopback
Do you see the problem? The issue is that “localhost” is resolvable from a public/routable IP address. This is known to cause all sorts of problems on Linux.
Given these misconfigurations and the problems they cause, Log Insight has added upgrade validation checks to limit their impact. So what does a proper /etc/hosts file look like? Configure LI through the supported OVF properties and see for yourself!
Summary
It is not recommended to make changes to the CLI of the Log Insight VA. If you do you may experience unexpected results and when asking for support you may be requested to reproduce the issue on a standard VA deployment. Note that the issues described in this post are generic to Linux and not specific to Log Insight.
© 2015, Steve Flanders. All rights reserved.
