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superuser2

On the same topic, what are the other pitfalls of re-using OS images?

I can think of:

- Hostname conflicts

- SSH key duplication

- Driver issues if the hardware is not the same

Are there more?

This seems like a compelling argument for bootstrapping new instances with configuration management, rather than trying to re-use OS images.

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Speaking of hostname conflicts: an ISP in Vietnam has configured all their devices to have a reverse DNS name of "localhost"

https://www.shodan.io/search?query=hostname%3Alocalhost

I've experienced this too - I seem to get a few people joining my gameserver from that ISP and I notice the DNS appeared as 'localhost'. Not ideal and I imagine it could break certain things. I always assumed it was a misconfigured internet cafe or something. 'Nice' to know it's a wider issue

MAC addresses. HP-UX saves them in its startup configs for some reason. A place I worked at used a sample build for its 'gold' build. All builds had the same MAC. Hilarity ensued.

MAC Address duplication on virtual interfaces for VMs started from a template.

Never seen this in years of using VMs

No (mainstream) Hypervisor does this and you'd run into networking problems pretty quickly if any of those VMs share a network.

Libvirt has serious issues with this https://www.redhat.com/archives/libvirt-users/2014-November/...

An alternative to typical configuration management (puppet, ansible, etc) is making your own OS installer. I've adapted the Ubuntu installer to turn a blank machine into a running instance of our app in just a couple of days. The client just has to pop-in the CD or flash drive, answer a couple of questions, and go grab a cup of tea while it installs.

>in just a couple of days

Days?! That is a crazy-long deploy time.

No, I meant it took me a couple of days to make the installer :-)

.. here I thought you were talking about the normal speed of cloudformation to boot up EC2 instances..

You jest, but our previous "cloud" provider (which we used in 2012/13) took more than that to provision a bog standard Linux VPS - and they often got the distro wrong!

Even things like /etc/machine-id

shared inode number

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