Quiet vs loglevel=3 in GRUB_CMDLINE_LINUX_DEFAULT


I see this in grub conf after install:

GRUB_CMDLINE_LINUX_DEFAULT=“quiet loglevel=3 nowatchdog”

I thought that quiet was the same thing as loglevel=4, so seeing the two on the same line makes no sense to me.

A source for this: https://unix.stackexchange.com/questions/306017/kernel-parameter-quiet-versus-loglevel-4-and-debug-versus-loglevel-7

Am I missing something ?

Welcome to the forum!

Does this answer your question?


I am by no means a grub parameter guru… But seems these are not the same thing and loglevel is an additional option.


If you are still getting messages printed to the console, it may be dmesg sending you what it thinks are important messages. You can change the level at which these messages will be printed by using quiet loglevel=<level> , where <level> is any number between 0 and 7, where 0 is the most critical, and 7 is debug levels of printing.

I have never tried removing quiet but that stackexchange answer certainly conflicts with the arch wiki which states that both are required.

Note that this only seems to work if both quiet and loglevel=<level> are both used, and they must be in that order (quiet first).

It would be easy enough to test if someone was motivated.

Yes, those two sources conflict.

The official kernel doc is less than helpful:
quiet [KNL] Disable most log messages

I’ll do some tests.

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edited several times because wrong tests.

quiet does change the behaviour compared to loglev4 alone: I saw nothing but a tiny message (I assume from ext4, saying the filesystem checks out) with it, and a lot of messages without.

1° I, the SE answer, and its source http://files.kroah.com/lkn/ are wrong about the semantics of quiet.
2° the wiki looks right; EOS’s grub is correct.
3° the kernel doc couldn’t be less specific if it tried. What are “most” messages?

Thanks, and have a nice day.

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Did you already take a look at this?

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

from: https://www.kernel.org/doc/html/latest/admin-guide/kernel-parameters.html

Yes, of course.

The question was, if quiet is equivalent to loglevel=4, then it seems strange to have a line that says “loglevel=4 loglevel=3”.

The conclusion of some cursory testing is that quiet is not equivalent to loglevel=4.

What remains open is a more specific statement as to what quiet does; is it loglevel=N for some N (!= 4), or something entirely different?

As in the link I posted above says to my understanding, quiet switches off all messages, loglevel is an option to allow certain system messages to pass through.

Options are also described here briefly:

You guys are quoting the same book. Keep in mind, there is a disclaimer in that book that reads:

The book is current as of the 2.6.18 kernel release

So, a bit out-of-date at this point.

quiet definitely doesn’t switch them all off.


It seems quiet does what the doc says it does, namely:

Disable most log messages

I fail to see why it should be equivalent to any loglevel=N.

Ah! I didn’t see the disclaimer. quiet having changed semantics since… 2006?.. would explain the confusion and seems quite likely.

I had a source (out of date, as it turns out) that claimed it was, and I was trying to make sense of the apparent contradiction. Nothing more.

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Oops. More correct to say it switches all the messages off the can be enabled by different log levels I assume?

:rofl: that what happens when reading the forum on the phone. Things are too small for me.

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No, it doesn’t do that either. It switches off most, but not all of the messages.


What about the nowatchdog option, I see that a lot but never checked what that is for and why appended to quiet?

No relation to quiet.

Watchdog auto reboots hung systems. Useful for servers, less for desktop.

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