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Timeline for Understand logging in Linux

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Feb 10, 2020 at 6:34 comment added antijon @MariusGedminas The syslog protocol is documented in RFC 5424 (tools.ietf.org/html/rfc5424)
Jan 9, 2018 at 13:15 comment added Marius Gedminas Is the syslog protocol documented somewhere?
Mar 28, 2017 at 12:44 comment added Flavius systemd has its own logging mechanisms, but that story would have to be told by somebody else. :) -- Please you tell, you got talent :-)
Jun 4, 2015 at 7:43 history bounty awarded Martin
Jun 4, 2015 at 7:43 vote accept Martin
Jun 3, 2015 at 16:08 comment added lcd047 @Martin /proc/kmsg is not a regular file, there is nothing "stored" there, rather it's just a view of the kernel's ring buffer. You can read it with cat precisely because you have no klogd(8) running (should you run klogd(8), cat /proc/kmsg would block). dmesg(1) reads messages from /dev/kmsg rather than /proc/kmsg; and it can also clear the buffer if you tell it to.
Jun 3, 2015 at 14:35 comment added Martin @lcd047, @sourcejedi, Thanks for replies! I had one Debian 7 system with rsyslogd running and one Ubuntu 12.04 with syslog-ng running and they both had file /proc/kmsg open according to lsof, i.e. klogd was not used. Another interesting thing which I noticed is that log messages are stored in /proc/kmsg file if no syslog daemon is running and one can view those with for example cat or text editor. However, it's only possible to view those messages once because they disappear after viewing. Last but not least, executing dmesg does not clear the content of /proc/kmsg file.
Jun 1, 2015 at 9:21 comment added lcd047 @Thushi Yes: synchronous writing of logs for busy daemons can lead to I/O performance issues. On the other hand, asynchronous writing of logs can lead to message loss.
Jun 1, 2015 at 9:05 comment added Thushi Because of these logs...Did you find any system performance issues?
May 30, 2015 at 11:05 comment added lcd047 @sourcejedi I haven't followed Linux all that closely in more than a few years now, but IIRC rsyslog doesn't use klogd(8) because its roots go way back, not because it recently made an explicit decision to do away with it. My memory can be failing though. Anyway, like I said, I was only trying to cover "classic" logging.
May 30, 2015 at 9:29 comment added sourcejedi nit: rsyslog is more popular now (default for Fedora, Debian), and it doesn't use a separate klogd. Looks like syslog-ng doesn't (by preference) either.
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May 29, 2015 at 18:57 history answered lcd047 CC BY-SA 3.0