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* MYSQL WON'T START OR STOP?:
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=============================
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You may never ever delete the special mysql user "debian-sys-maint". This
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user together with the credentials in /etc/mysql/debian.cnf are used by the
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init scripts to stop the server as they would require knowledge of the mysql
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root users password else.
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So in most of the times you can fix the situation by making sure that the
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debian.cnf file contains the right password, e.g. by setting a new one
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(remember to do a "flush privileges" then).
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* WHAT TO DO AFTER UPGRADES:
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============================
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The privilege tables are automatically updated so all there is left is read
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the changelogs on dev.mysql.com to see if any changes affect custom apps.
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* WHAT TO DO AFTER INSTALLATION:
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================================
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The MySQL manual describes certain steps to do at this stage in a separate
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chapter. They are not necessary as the Debian packages does them
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The only thing that is left over for the admin is
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- setting the passwords
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- creating new users and databases
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- read the rest of this text
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* DOWNGRADING TO 4.0 or 4.1:
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============================
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But if you do and get problems or make interesting experiences, mail me, it
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Ok, if you really want, I would recommend to "mysqldump --opt" all tables,
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then purge 4.1, delete /var/lib/mysql, install 4.0 and insert the dumps. Be
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carefully, though, with the "mysql" table, you might not simply overwrite that
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one as the password for the mysql "debian-sys-maint" user is stored in
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/etc/mysql/debian.cnf and needed by /etc/init.d/ to start mysql and check if
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* SOME APPLICATION CAN NO LONGER CONNECT:
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=========================================
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This application is probably linked against libmysqlclient12 or below and
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somebody has created a mysql user with new-style passwords.
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The old_passwords=1 option in /etc/mysql/my.cnf might help. If not the
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application that inserted the user has to be changed or the application that
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tries to connect updated to libmysqlclient14 or -15.
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For security reasons, the Debian package has enabled networking only on the
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loop-back device using "bind-address" in /etc/mysql/my.cnf. Check with
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"netstat -tlnp" where it is listening. If your connection is aborted
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immediately see if "mysqld: all" or similar is in /etc/hosts.allow and read
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* WHERE IS THE DOCUMENTATION?:
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==============================
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Unfortunately due to licensing restrictions, debian currently not able
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to provide the mysql-doc package in any format. For the most up to date
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documentation, please go to http://dev.mysql.com/doc.
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It is strongly recommended to set a password for the mysql root user (which
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/usr/bin/mysql -u root -D mysql -e "update user set password=password('new-password') where user='root'"
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/usr/bin/mysql -u root -e "flush privileges"
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If you already had a password set add "-p" before "-u" to the lines above.
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If you are tired to type the password in every time or want to automate your
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scripts you can store it in the file $HOME/.my.cnf. It should be chmod 0600
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(-rw------- username username .my.cnf) to ensure that nobody else can read
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it. Every other configuration parameter can be stored there, too. You will
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find an example below and more information in the MySQL manual in
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/usr/share/doc/mariadb-doc or www.mysql.com.
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ATTENTION: It is necessary, that a .my.cnf from root always contains a "user"
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line wherever there is a "password" line, else, the Debian maintenance
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scripts, that use /etc/mysql/debian.cnf, will use the username
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"debian-sys-maint" but the password that is in root's .my.cnf. Also note,
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that every change you make in the /root/.my.cnf will affect the mysql cron
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# an example of $HOME/.my.cnf
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user = your-mysql-username
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password = enter-your-good-new-password-here
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* BIG_ROWS FOR EVEN MORE ROWS IN A TABLE:
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=========================================
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If you ever run out of rows in a table there is the possibility of building
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the package with "-DBIG_ROWS" which, according to a MySQL employee on
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packagers@lists.mysql.com should lead to a 64bit row index (I guess > 2^32
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rows) but also to an approx. 5% performance loss.
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* BerkeleyDB Storage Engine
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===========================
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Support for BerkeleyDB has been removed in 5.1, and consequently both the
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have-bdb and skip-bdb configuration options will cause the server to fail.
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Removing the options from /etc/mysql/my.cnf will fix this problem.
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* FURTHER NOTES ON REPLICATION
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===============================
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If the MySQL server is acting as a replication slave, you should not
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set --tmpdir to point to a directory on a memory-based filesystem or to
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a directory that is cleared when the server host restarts. A replication
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slave needs some of its temporary files to survive a machine restart so
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that it can replicate temporary tables or LOAD DATA INFILE operations. If
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files in the temporary file directory are lost when the server restarts,