current colleague asked me how to cut down the console generation of
kernel messages on a system that uses the original syslog, not rsyslog
or syslog-ng, and since i'm currently using systemd/journalctl, i
can't really test this so here's what should be a simple question.
my first suggestion was just configure /etc/sysctl.conf in userspace
to avoid the console display of low-priority (debug, info) kernel
messages -- send them to a file, or /dev/null, or whatever. because if
the current setting in /etc/sysctl.conf is:
kern.* /dev/console
well, that's kind of where the problem is.
however, an extra restriction is that i am not allowed to mess with
anything in userspace, so tweaking /etc/sysctl.conf is out. so i
checked out the "loglevel" kernel parameter, which is explained
thusly:
loglevel= All Kernel Messages with a loglevel smaller than the
console loglevel will be printed to the console. It can
also be changed with klogd or other programs. The
loglevels are defined as follows:
0 (KERN_EMERG) system is unusable
1 (KERN_ALERT) action must be taken immediately
2 (KERN_CRIT) critical conditions
3 (KERN_ERR) error conditions
4 (KERN_WARNING) warning conditions
5 (KERN_NOTICE) normal but significant condition
6 (KERN_INFO) informational
7 (KERN_DEBUG) debug-level messages
so it *appears* that if i wanted only(?) emerg and alert messages sent
to the console, i would set "loglevel=2" at the command line.
but from the explanation, i'm not convinced that's a solution
because the above says only that those two priorities would be sent to
the console -- it says nothing about what would happen to all of the
others. specifically, it's not clear to me how setting loglevel on the
command line interacts with that is *already* in /etc/sysctl.conf.
what if /etc/sysctl.conf does indeed contain the line:
kern.* /dev/console
how does loglevel interact with that? does it override it? or does it
complement it? or what if /etc/sysctl.conf contained the line:
kern.* /dev/null
would the loglevel setting override that?
in short, is there a way on the kernel command line to reduce the
generation of kernel messages to the system console, regardless of the
settings in /etc/sysctl.conf?
rday
--
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Robert P. J. Day Ottawa, Ontario, CANADA
http://crashcourse.ca/dokuwiki
Twitter: http://twitter.com/rpjday
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