I need pdf,demystification-explanation contex in log messages /var/log/...

I get the impression that you are asking for some sort of coherent explanation of /var/log.

Meanwhile, your question appears to not be very clear or coherent.

Can you offer a better explanation as to what you're looking for? As well as indicate what information you've already found, or started with?

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/var/log is the default location for a system's log files. If you try hard enough, you can configure your system to put all of its logs somewhere else. I can't imagine that anyone has. Almost every system runs the system logger daemon, syslogd, which puts its files where /etc/syslog.conf tells it to. /var/log/syslog contains 'important' system messages; /var/log/messages less-important messages; maillog contains the SMTP server's logs - and there are dozens more. It may be a better tactic for you to ask specific questions than ask for a complete treatise.

log entries usually contain a time stamp and the name of the program that recorded them; they are usually on a single line.

I need pdf book with more details like: https://www.loggly.com/ultimate-guide/category/linux/

Suggest you try The Linux Documentation Project and in the Search window, try syslog, or logging, and view some of the results. Also note that there are PDF forms of the documentation on that site as well as HTML text, or other.

Hi,

The linked PDF above provides good explanation for the log system. What do you expect from a different author that would describe the same?

What part of that PDF do you not understand?

Here is link found using DuckDuckGo; https://www.lifewire.com/introductio...-files-2192233

Maybe if you do a search on your own then you will find information suited to your needs. The two links on this page provide more than enough information to suit most queries.

I do suggest that you read https://www.linuxquestions.org/quest...#faq_lqwelcome so you can compose a good post/thread to help us to help you in the future.

Hope this helps.
Have fun & enjoy!