Ok, first, sorry for this question, I usually search a lot before post a question on any forum or Q&A. But now I'm on panic, I need help (also to keep my job). :)

This morning the server I manage who host many websites of clients of the company where I work had a problem. The error when I try to visit one of the website is simply:

Error establishing a database connection

First I've tried to login into plesk, but the error was the same (failed to connect to the DB) So I tried to restart the entire VPS, but nothing to do the error still there, so I connected through ssh and I tried with:

sudo /etc/init.d/mysql start

I check for the mysql logs and it was empty except for this:

160801 08:07:11 mysqld_safe Starting mysqld daemon with databases from /var/lib/mysql 160801 8:07:11 [Warning] Using unique option prefix key_buffer instead of key_buffer_size is deprecated and will be removed in a future release. Please use the full name instead. 160801 8:07:11 [Note] /usr/sbin/mysqld (mysqld 5.5.46-0ubuntu0.14.04.2) starting as process 5448 ... 160801 8:07:11 [ERROR] COLLATION 'utf8mb4_unicode_ci' is not valid for CHARACTER SET 'utf8' 160801 8:07:11 [ERROR] Aborting

160801 8:07:11 [Note] /usr/sbin/mysqld: Shutdown complete

160801 08:07:11 mysqld_safe mysqld from pid file /var/run/mysqld/mysqld.pid ended

I really don't know what happened but I think the problem could be that error in the log.

  • -1 ServerFault is a Q & A platform and not a forum. Even as the OP you can post an answer and accept it as the solution. Please don't edit your and rename your question to include the answer – HBruijn Aug 1 '16 at 8:03
  • Ok thanks a lot, sorry, this morning I was a little bit in panic (I'm sure you know what I mean). – Gianca Aug 1 '16 at 13:00

I resolved the issue in this way.

I've opened the file /etc/mysql/my.cnf with nano.

sudo nano /etc/mysql/my.cnf

And I've commented this line:

collation-server = utf8mb4_unicode_ci

I tried to start the mysql again and now it works.

I don't know exactly why it happened, and I'm still investigating about.

I hope this could be helpful to someone else.

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