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Mac Mini Server Tips: Lights Out Management
Monday, February 13, 2012 - 3:22 AM EST
Posted by: Jon Schwenn

Lights Out Management (LOM) is one of the features that existed on the Xserve platform, but fails to exist on any other server option from Apple. In fact, it might be the most important missing feature. To answer what LOM is, I'll quote Apple Knowledge Base's article TA24506:

"Lights Out Management (LOM) is Apple's implementation of the remote monitoring and management protocol Intelligent Platform Management Interface (IPMI) developed by Intel.

The addition of Lights Out Management to Xserve provides for the monitoring of over 100 sensors that measure voltage, temperature, fan speeds, etc. Using Server Monitor, one can get a fairly complete picture of the health of an Xserve.

In addition to monitoring LOM can also be used to control some functions of an Xserve. Xserve can be shutdown or restarted from a remote location via the implementation of LOM in Server Monitor. Even if the Xserve is in an unresponsive state, one should be able to gain access via LOM."

For the most part, I'd say these capabilities are not required for your daily tasks. These come into play mostly when you have a Mac server located at an off-site facility. It may be another office or a data center. Inevitably there is chance that the machine locks up, or that it is accidentally shut down, or that it is put to sleep. These are scenarios where having LOM access would allow an administrator to get the server back online remotely. Unfortunately it is doubtful that the Mac mini Server would ever include these LOM features.

We can reduce downtime and bring some of the characteristics of LOM to a Mac mini Server by how we configure the Energy Saver Preferences. There are some basics, such as setting the machine to never fall asleep. But we also want to make sure that the machine will wake for network access, and restart if there is a power failure or if there is a kernel panic. The other part to this is a remote controlled power outlet. Normally this is an option for Power Distribution Units (PDUs).

Now if the machine does lock up, but fails to restart itself, the power outlet can be power cycled and the machine will power back up once power has been restored. Keep in mind that this should not be a common occurrence and that damage to the file system is possible. If the machine was accidentally put into sleep mode, you can use another machine on the network to wake it up. One tool that would allow you do this is WakeOnLan.

This puts us in a fairly good spot in regards to managing a Mac mini server that is running headless and off-site. Unfortunately there is still one aspect of LOM that we have not touched on yet. Cold booting a server remotely is impossible without LOM. If you accidentally shut down the machine, no amount of cycling the power to the machine will make it power on. Sure you can edit the Apple menu xib file to remove the shutdown option, but do you really want to be modifying the OS at that level?

If you click the schedule button in the bottom right corner of the Energy Saver Preferences, there is another option available. Your own scenario might dictate how you would use this feature. In the event that the machine is accidentally shut down from a remote connection (left connected to power and network), the machine would boot itself up at the time you set. Unfortunately there is only a way to schedule one event per day. If the machine is running, this setting does not do any harm. If there is a specific time that the machine would need to be online, but would not be physically accessible this option works out well. Usually something like midnight, or before a third shift starts, in time for nightly scripts to run, or 5 AM before people come in for the workday.

This Mac mini Server tip was provided by Jon Schwenn from Mac Mini Vault. Jon has been managing Linux and Mac web servers for over a decade. His certifications include ACTC and RHCE.

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