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By Jonathan Corbet May 27, 2021 When kernel developers want to communicate something about the state of a running kernel, they tend to use printk(); that results in a log entry that is intended — with varying success — to be human-readable. As it happens, though, the consumers of that information are often not human; the kernel's log output is also read by automated monitoring systems that are looking for problems. The result is an impedance mismatch that often ends with the monitoring system missing important messages. The printk() format indexing patch set is the latest of many attempts to improve this situation.
Monitoring systems are installed by administrators who want to know when there is a problem with the systems they manage. So, for example, if the CPU bursts into flames, and the administrator doesn't happen to be in the room to witness the event, they would at least like to receive an alert telling them to call their hardware vendor and the fire department, probably in that order. To produce this alert, the monitoring system will be watching the kernel log for the "CPU on fire" message printed by the relevant code in the kernel. If all goes well, the message will escape before the CPU melts and the replacement system can be ordered in a timely manner.