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Mastering CoreOS by Sreenivas Makam

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Basic debugging

The following are some basic debugging tools and approaches to debug issues in the CoreOS cluster.

journalctl

Systemd-Journal takes care of logging all the kernel and systemd services. Journal log files from all the services are stored in a centralized location in /var/log/journal. The logs are stored in the binary format, and this keeps it easy to manipulate to different formats.

Here are some common examples that shows how to use Journalctl:

  • Journalctl: This lists the combined journal log from all the sources.
  • Journalctl –u etcd2.service: This lists the logs from etcd2.service.
  • Journalctl –u etcd2.service –f: This lists the logs from etcd2. service like tail –f format.
  • Journalctl –u etcd2.service –n 100: This lists the logs of the last ...

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