I am completely new in Linux. What I see are two logs that run approximately in the same way. Why there are two logs? What kind of messages I expect to see in each of them? And what is the difference in their life cycle?

closed as unclear what you're asking by Anthony Geoghegan, phk, user34720, Jeff Schaller, GAD3R May 25 '17 at 11:39

Please clarify your specific problem or add additional details to highlight exactly what you need. As it's currently written, it’s hard to tell exactly what you're asking. See the How to Ask page for help clarifying this question. If this question can be reworded to fit the rules in the help center, please edit the question.

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    I'd suggest a peek in the How to Ask guide, esp. the first point. – ilkkachu May 25 '17 at 10:08

They are two totally different things.

On most systems that I'm aware of that has dmesg, it is sometimes a command and sometimes a log file in /var/log, and may be both. The log contains messages produced by the kernel. This will usually include the various device probe messages during the boot sequence as well as any further messages outputted by the kernel during the running of the system.

Depending on what "journal" refers to, I suppose it way be different things. The journal that first springs to my mind is the journal of a journaled filsystem. This journal contains the various transactions made to a particular partition (part of a disk) and allows the system to replay disk operations consistently in the case of a system crash. This journal is not generally accessible to users.

If "journal" refers to journalctl, then the two are similar, but not the same. journalctl has a --dmesg option that makes it mimic dmesg.

Compare the manuals for journalctl and dmesg on your system.

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    Or perhaps systemd-journal, it fits the question more. Just guessing... – schaiba May 25 '17 at 11:47
  • @schaiba Could be, but I'm not on Linux, so it's nothing I can write anything about... Saw the tag now. I'll update if the question is made clearer. – Kusalananda May 25 '17 at 11:49

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