[CentOS] SOLVED: MySQL ERROR - UNKNOWN_MYSQL_USER

Thu Jul 21 12:21:57 UTC 2011
Keith Roberts <keith at karsites.net>

On Thu, 21 Jul 2011, Markus Falb wrote:

> To: centos at centos.org
> From: Markus Falb <markus.falb at fasel.at>
> Subject: Re: [CentOS] MySQL ERROR - UNKNOWN_MYSQL_USER
> 
> On 20.7.2011 23:07, Keith Roberts wrote:
>> This is strange behavior because as soon as I start mysqld
>> with a clean error log, I get the following messages:
>>
>> 110720 21:38:47 [Note] /usr/libexec/mysqld: ready for
>> connections.
>> Version: '5.5.14-log'  socket: '/var/lib/mysql/mysql.sock'
>> port: 2500  MySQL Community Server (GPL) by Remi
>>
>> 110720 21:38:48 [Warning] Access denied for user
>> 'UNKNOWN_MYSQL_USER'@'localhost' (using password: NO)
>>
>> The strange things is, AFAIK there are no clients trying to
>> connect to mysql. I shutdown a mysql CLI monitor I had
>> running, and did the restart again.
>>
>> So I'm just wondering why I get this message, when AFAIK
>> there is nothing that should be trying to connect to mysql -
>> unless it's a server daemon running somewhere?
>>
>> Has anyone else come across this funny error message?
>
> Please have a look at the initscript /etc/init.d/mysqld
>
> ...snip
> # Spin for a maximum of N seconds waiting for the server to come up.
> # Rather than assuming we know a valid username, accept an "access
> # denied" response as meaning the server is functioning.
> snap...

Hi Markus.

Thanks for that detailed explanation.

I've checked the /etc/init.d/mysqld file, and like you say, 
it's the mysqld script itself, using the --user=UNKNOWN_MYSQL_USER
option to test the mysql server is up and running.

So at least I know what is causing this error, and the 
reason for it:

TIMEOUT="$STARTTIMEOUT"
while [ $TIMEOUT -gt 0 ]; do
   RESPONSE=`/usr/bin/mysqladmin --socket="$socketfile" --user=UNKNOWN_MYSQL_USER ping 2>&1`

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