IPMI and the BMC
Every server has a small management computer on the motherboard that runs whether or not the server itself is on. It is enormously useful and, exposed, enormously dangerous.
What it is
The Baseboard Management Controller is an independent processor with its own firmware, its own network interface and its own power. It can read every sensor, log hardware events, power the machine on and off, and present a remote console and virtual media — all with the main system switched off.
IPMI is the protocol used to talk to it. In practice people say IPMI when they mean the BMC's web interface, and the difference rarely matters in conversation.
Why it must never face the internet
BMC firmware has a long history of serious vulnerabilities, ships with default credentials, and is updated far less often than anything else in the building. It also sits below your operating system: whoever controls it can mount an image, boot from it and read your disks. Your firewall, your SSH keys and your careful hardening are all above that line and none of them apply.
Internet-wide scans find tens of thousands of exposed BMCs at any moment. They are found within minutes of appearing. There is no safe way to leave one open.
How this works with us
Management interfaces live on a separate network that is not reachable from the internet. You get the useful parts — remote console, power control, boot device selection, sensor readings — through the portal, which fronts them for you. That is what remote KVM describes, and it is included on every machine rather than sold as an extra.
If you need deeper access for automation, ask support. There are ways to arrange it that do not involve putting a BMC on a public address.
If you colocate your own hardware
This is where it matters most, because the BMC is yours. Before the machine is racked:
- Change every default credential, including the ones you did not know existed. Check the manual for a second account.
- Never share one BMC password across a fleet. One compromised machine then means one compromised machine, instead of all of them.
- Disable IPMI over LAN if you only use the web interface, and disable the cipher 0 null-authentication mode if your firmware still offers it.
- Update the firmware before it goes in. It is much easier on your desk than in a rack.
- Tell us if you want the management port connected at all, and to what. The default is that it is not reachable from the internet.
Reading it from the operating system
You do not need network access to the BMC to read its event log from the machine itself:
ipmitool sel list — hardware events, including memory and
power faults, surviving reboots
ipmitool sdr list — temperatures, fan speeds, voltages
These are the first two commands to run when a machine behaves oddly and the operating system logs show nothing. See memory errors and hardware failure.
Still stuck? Mail support@novogara.com — an engineer answers, at any hour. Back to the knowledge base