Difference between revisions of "MySQL"

Revision as of 22:53, 4 September 2012

MySQL is a widely spread, multi-threaded, multi-user SQL database. For more information about features, see the official homepage.

Installation

Install the mysql package which is available in the official repositories.

After installing MySQL, you should run the setup script as root:

# rc.d start mysqld && mysql_secure_installation

Then restart MySQL:

# rc.d restart mysqld

To start MySQL automatically at boot, edit /etc/rc.conf and add mysqld to the DAEMONS array.

If you have switched to systemd enable it with:

# systemctl enable mysqld.service

Configuration

Once you have started the MySQL server, you probably want to add a root account in order to maintain your MySQL users and databases. This can be done manually or automatically, as mentioned by the output of the above script. Either run the commands to set a password for the root account, or run the secure installation script.

You now should be able to do further configuration using your favorite interface. For example you can use MySQL's command line tool to log in as root into your MySQL server:

$ mysql -p -u root

Enable remote access

The MySQL server does not listen on the TCP port 3306 by default. To allow (remote) TCP connections, comment the following line in /etc/mysql/my.cnf:

skip-networking

Upgrading

You might consider running this command after you have upgraded MySQL and started it:

# mysql_upgrade -u root -p

Running multiple instances (MySQL 4 and MySQL 5)

MySQL4: You can get the MySQL binaries from here It is best to install them into:

/usr/local/mysql

Copy the start-up script to:

/etc/rc.d 

as instructed in the README:

# cp  /usr/local/mysql/support-files/mysql.server /etc/rc.d/mysqld4

In the start-up script, it helps to explicitly set

Basedir=/usr/local/mysql
pid_file=/usr/local/var/run/mysql/mysql4.pid 

(make sure the referenced directories are created with suitable permissions)

Copy your choice of config file:

# cp /usr/local/mysql/support-files/my-medium.cnf /usr/local/mysql/data/my.cnf

In the config file, set the socket file and the TCP/IP port:

[client]
port            = 3307
socket          = /usr/local/var/run/mysql/mysql4.sock

[mysqld]
port            = 3307
socket          = /usr/local/var/run/mysqld/mysql4.sock

MySQL5: The default start-up script in:

/etc/rc.d/mysqld 

does not handle multiple instances of mysql.

Edit the file. Find this line:

getPID() {
  echo $(pgrep -u mysql mysqld 2>/dev/null);
}

And replace it with:

getPID() {
  echo $(pgrep -u mysql -f /usr/bin/mysqld 2>/dev/null);
}

Start up the services:

/etc/rc.d/mysqld start
/etc/rc.d/mysqld4 start

Optional, start the services automatically (in /etc/rc.conf). Add the following two daemons to the DAEMONS array:

• mysqld4
• mysqld

That should be it!

Troubleshooting

MySQL daemon cannot start

If you see something like this:

 # /etc/rc.d/mysqld restart
 :: Stopping MySQL  [FAIL] 
 :: Starting MySQL  [FAIL]

and there is no entry in the log files, you might want to check the permissions of files in the directories /var/lib/mysql and /var/lib/mysql/mysql. If the owner of files in these directories is not mysql:mysql, you should do the following:

 # chown mysql:mysql /var/lib/mysql -R

If you run into permission problems despite having followed the above, ensure that your my.cnf is copied to /etc/:

 # cp /etc/mysql/my.cnf /etc/my.cnf

Now try and restart the daemon.

If you get these messages in your /var/lib/mysql/hostname.err

 [ERROR] Can't start server : Bind on unix socket: Permission denied
 [ERROR] Do you already have another mysqld server running on socket: /var/run/mysqld/mysqld.sock ?
 [ERROR] Aborting

you should change permissions of /var/run/mysqld like so:

 # chown mysql:mysql /var/run/mysqld -R

If you run mysqld and the following error appears:

 Fatal error: Can’t open and lock privilege tables: Table ‘mysql.host’ doesn’t exist

Run the following command from the /usr directory to install the default tables:

 # cd /usr
 # mysql_install_db --user=mysql --ldata=/var/lib/mysql/

Unable to run mysql_upgrade because MySQL cannot start.

Try run MySQL in safemode:

# mysqld_safe --datadir=/var/lib/mysql/

And then run:

# mysql_upgrade -u root -p

How to Reset the Root Password

Stop the mysqld daemon

# /etc/rc.d/mysqld stop
# mysqld_safe --skip-grant-tables &

Connect to the mysql server

# mysql -u root mysql

Change root password:

 mysql> UPDATE mysql.user SET Password=PASSWORD('MyNewPass') WHERE User='root';
 mysql> FLUSH PRIVILEGES;
 mysql> exit

Then restart the daemon:

# /etc/rc.d/mysqld restart

You are done.

How to Enable Auto-completion

On Arch, the MySQL client completion feature is disabled by default. To enable it system-wide edit /etc/mysql/my.cnf, search for no-auto-rehash and replace it by :

#no-auto-rehash
auto-rehash

Completion will be enabled next time you run the MySQL client. Please note that enabling this feature can make the client initialization longer.

More Resources

• LAMP - Arch wiki article covering the setup of a LAMP server (Linux Apache MySQL PHP)
• http://www.mysql.com/
• Front-ends: mysql-gui-tools^AUR mysql-workbench^AUR