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