Difference between revisions of "MySQL"

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(How to enable auto-completion)
(removed section that was outdated. no one should still be using mysql4 anyway)
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You might consider running this command after you have upgraded MySQL and started it:
 
You might consider running this command after you have upgraded MySQL and started it:
 
  # mysql_upgrade -u root -p
 
  # mysql_upgrade -u root -p
 
== Running multiple instances (MySQL 4 and MySQL 5)==
 
MySQL4:
 
You can get the MySQL binaries from [http://dev.mysql.com/downloads/mysql/4.1.html#downloads 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 {{ic|/etc/[[rc.conf]]}}). Add the following two daemons to the DAEMONS array:
 
*mysqld4
 
*mysqld
 
 
That should be it!
 
  
 
== Troubleshooting ==
 
== Troubleshooting ==

Revision as of 20:50, 14 November 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, start the daemon and run the setup script:

# systemctl start mysqld
# mysql_secure_installation

Then restart MySQL:

# systemctl restart mysqld

To start MySQL automatically at boot:

# systemctl enable mysqld

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

Troubleshooting

MySQL daemon cannot start

If you see something like this:

 :: 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 start 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

The permissions of /var/run/mysqld could be the culprit.

 # 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

Reset the root password

Stop the mysqld daemon

# systemctl stop mysqld
# 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

And restart the daemon:

# systemctl restart mysqld

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, and replace no-auto-rehash by 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.

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