Tech Talk Live Blog

Virtual Appliances and Serial Ports

Brian Steigauf

I love virtual appliances. All of the ease of use, none of their subpar hardware. If you already have a highly available, redundant virtual infrastructure, why would you add hardware that is outside of your control? Plus, you can replicate the “appliance” to have a cold standby that you can bring up in minutes, should there be a problem.

Recently, I have run into some issues with virtual appliances and the latest VM hardware version in VMware 6.0 update 2 (VM version 11). With VM hardware 11, there are some changes to the underlying virtual hardware relating to serial ports. We run Kemp Virtual LoadMaster appliances and had to open a case because the appliances were generating an error every minute stating “ttyS0: ioctl: Input/output error” and “init: Id “S0” respawning too fast: disabled for 5 minutes.”

A quick Google search revealed results for Linux distributions that all referenced serial ports. “But these do not have serial ports,” was my thought. Kemp support was quick to offer a work around. . . add a serial port to the VM and direct its output to a file. Sure enough, adding the serial port fixed the problem. (See here for how to add a serial port to a VM.)

We are also utilizing Infoblox virtual appliances for DNS and IPAM. Fast forward a couple of weeks, I needed to restart our Grid Master appliance for our Infoblox environment (our environment is a Grid Master inside the network with two slave DNS appliances on the outside). While starting up, the appliance would go through its normal POST and get so far in the boot process and stop at the screen that said “Emergency prompt not entered, continuing to boot.” I ran into the same issue a couple weeks prior when we upgraded our Infoblox environment to 8.0.1 with the outside slave appliances. The fix from Infoblox was to redeploy those servers as new 8.0.1 appliances and resync the databases. I did not have that luxury with the Grid Master and my suspicion that the replica VM would be affected by the same issue, was confirmed. I opened a case with Infoblox support with mild panic setting in. As I was put on hold to talk to the engineer, I had a revelation, “what if the appliance was looking for a serial port?” I quickly added a serial port, redirected the output to a file on the replica, and started it up. It paused at the “Emergency prompt not entered, continuing to boot” screen, then proceeded to boot. I told the engineer that I fixed the problem and performed the same procedure on the production appliance. I asked if they had similar experiences with other customers running virtual appliances and was told they were not aware of the issue. I also explained I had run into the issue previously with two other virtual appliances and it might be something they may want to add to their knowledge base. I could not believe I was the only person that had run into this issue, and hope this post may help anyone else who finds themselves in a similar predicament.

Tech Talk Live Blog Comment Guidelines:

One of our main goals at Tech Talk Live is to build a community. It is our hope that this blog can be a forum for discussion around our content. We see commenting as an integral part of this community. It allows everyone to participate, contribute, connect, and share relevant personal experience that adds value to the conversation. Respect counts. We believe you can disagree without being disagreeable. Please refrain from personal attacks, name calling, libel/defamation, hate speech, discriminatory or obscene/profane language, etc. Comments should keep to the topic at hand, and not be promotional or commercial in nature. Please do not link to personal blog posts, websites, or social media accounts that are irrelevant to the conversation. This is considered self-promotion. We welcome links that help further the conversation and reserve the right to delete those we deem unnecessary. The appearance of external links on this site does not constitute official endorsement on behalf of Tech Talk Live or Lancaster-Lebanon Intermediate Unit 13. You are solely responsible for the content that you post – please use your best judgment. We reserve the right to remove posts that do not follow these guidelines.

Leave a Reply

Your email address will not be published. Required fields are marked *


Tech Talk Live is the only conference of its kind in the region specifically designed for IT pros in education.

1020 New Holland Avenue, Lancaster, PA 17601

(717) 606-1770