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* REMEMBER TO SET THE ROOT PASSWORD !!!
============================================================================
* MYSQL WON'T INSTALL?
======================
MySQL will only install if you have a non-numeric hostname that is resolvable
via the /etc/hosts file. E.g. if the "hostname" command returns "myhostname"
then there must be a line like "10.0.0.1 myhostname".
On upgrades from MySQL 3.23, as shipped with Debian Woody, symlinks in place of
/var/lib/mysql or /var/log/mysql gets accidently removed and have manually be
restored.
* MYSQL WON'T START OR STOP?
============================
You may never ever delete the special mysql user "debian-sys-maint". This
user together with the credentials in /etc/mysql/debian.cnf are used by the
init scripts to stop the server as they would require knowledge of the mysql
root users password else.
So in most of the times you can fix the situation by making sure that the
debian.cnf file contains the right password, e.g. by setting a new one
(remember to do a "flush privileges" then).
* WHAT TO DO AFTER UPGRADES:
============================
- running mysql_upgrade to be able to make use of possibly added new
privilege columns. This script does not give any use more rights.
* WHAT TO DO AFTER INSTALLATION:
================================
The MySQL manual describes certain steps to do at this stage in a separate
chapter. They are not necessary as the Debian packages does them
automatically.
The only thing that is left over for the admin is
- setting the *passwords* !!!
- creating new users and databases
- read the rest of this text
* DOWNGRADING TO 4.0 or 4.1:
============================
Unsupported. Period.
But if you do and get problems or make interesting experiences, mail me, it
might help others.
Ok, if you really want, I would recommend to "mysqldump --opt" all tables,
then purge 4.1, delete /var/lib/mysql, install 4.0 and insert the dumps. Be
carefully, though, with the "mysql" table, you might not simply overwrite that
one as the password for the mysql "debian-sys-maint" user is stored in
/etc/mysql/debian.cnf and needed by /etc/init.d/ to start mysql and check if
it's alive.
* SOME APPLICATION CAN NO LONGER CONNECT:
=========================================
This application is probably linked against libmysqlclient12 or below and
somebody has created a mysql user with new-style passwords.
The old_passwords option which forces backwards compatibility, can be set
in /etc/mysql/conf.d/old_passwords.conf.
If that does not help, the password can be set manually, the application that
inserted the user should be changed or the application that tries to connect
should be updated to libmysqlclient14 or -15.
Read http://dev.mysql.com/doc/refman/5.0/en/old-client.html
* NETWORKING:
=============
For security reasons, the Debian package has enabled networking only on the
loop-back device using "bind-address" in /etc/mysql/my.cnf. Check with
"netstat -tlnp" where it is listening. If your connection is aborted
immediately see if "mysqld: all" or similar is in /etc/hosts.allow and read
hosts_access(5).
* WHERE IS THE DOCUMENTATION?:
==============================
Unfortunately due to licensing restrictions, debian currently not able
to provide the mysql-doc package in any format. For the most up to date
documentation, please go to http://dev.mysql.com/doc.
* PASSWORDS:
============
It is strongly recommended to set a password for the mysql root user (which
is NOT the same as the "normal" root user) with the command:
/usr/bin/mysqladmin -u root password 'enter-your-good-new-password-here'
If you already had a password set add " -p " before "-u" to the line above.
If you are tired to type the password in every time or want to automate your
scripts you can store it in the file $HOME/.my.cnf. It should be chmod 0600
(-rw------- username username .my.cnf) to ensure that nobody else can read
it. Every other configuration parameter can be stored there, too. You will
find an example below and more information in the MySQL manual in
/usr/share/doc/mysql-doc or www.mysql.com.
ATTENTION: It is necessary, that a .my.cnf from root always contains a "user"
line wherever there is a "password" line, else, the Debian maintenance
scripts, that use /etc/mysql/debian.cnf, will use the username
"debian-sys-maint" but the password that is in root's .my.cnf. Also note,
that every change you make in the /root/.my.cnf will affect the mysql cron
script, too.
# an example of $HOME/.my.cnf
[client]
user = your-mysql-username
password = enter-your-good-new-password-here
* BIG_ROWS FOR EVEN MORE ROWS IN A TABLE:
=========================================
If you ever run out of rows in a table there is the possibility of building
the package with "-DBIG_ROWS" which, according to a MySQL employee on
packagers@lists.mysql.com should lead to a 64bit row index (I guess > 2^32
rows) but also to an approx. 5% performance loss.
* NDB CLUSTER ENGINE:
=====================
NDB is the shared-nothing cluster engine since MySQL-4.1.
This package contains the all three components, the mysql backend, the NDB
Data Node and the NDB Management Node. The init scripts of the cluster
daemons will silently exit unless their configuration is provided:
mysql-ndb: needs "ndb-connectstring" in /etc/mysql/my.cnf
mysql-ndb-mgm: needs /etc/mysql/ndb_mgmd.cnf
* EXPIRE_LOGS_DAYS AND LOG_BIN:
===============================
Having expire_logs_days enabled but log-bin not crashes the server. Using both
or none of those options is safe. To prevent this happening during the nightly
log rotation via /etc/logrotate.d/mysql the initscript checks for malicious
combination of options. This is Debian bug #368547 and MySQL bug #17733.
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