Keith Roberts wrote:

On Wed, 20 Jul 2011, Ljubomir Ljubojevic wrote:

...

To: CentOS mailing list centos@centos.org From: Ljubomir Ljubojevic office@plnet.rs Subject: Re: [CentOS] MySQL ERROR - UNKNOWN_MYSQL_USER

Keith Roberts wrote:

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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?

There must be some service that does uses MySQL but does not have user set. Website like CMS? Try getting more logs to see what app/script uses it.

Hi Ljubomir.

It might be collectd that can use mysql. The man page is over 5,000 pages for the config file. I seem to remember seeing a message at boot time about collectd not being configured properly to use mysql.

I installed collectd recently, so I could monitor my HDD temperatures using GKrellM, which it's doing OK.

Then all you need to do is "service collectd stop; service mysqld start" and check the logs.

On Thu, 21 Jul 2011, Markus Falb wrote:

To: centos@centos.org From: Markus Falb markus.falb@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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