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MySQL on Linux Tutorial

This tutorial covers the MySQL database running on a Linux server. This tutorial will also cover the generation and use a simple database. The interface language of the MySQL database is the standard SQL (Standard Query Language) which allows for inserts, updates and queries of data stored in relational tables. The SQL language is also used for the administration of the database for the creation and modification of tables, users and access privileges. Tables are identified by unique names and hold data in a row and column (record) structure. A fixed number of named columns are defined for a table with a variable number of rows.

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Related YoLinux Tutorials:

°List of Linux Databases

°MySQL InnoDB, Transactions & Foreign Keys

°MySQL Workbench

°SQL Workbench/J

°MySQL C API

°SQLite

°Apache, Tomcat, MySQL and Java

°YoLinux Tutorials Index




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The MySQL Database Installation and configuration:
YoLinux.com Tux database image

Red Hat / Fedora Core RPM Packages:

  • mysql-version.rpm (Required)
  • mysql-server-version.rpm (Required)
  • mysqlclient9-version.rpm (Shared object libraries)
  • mysql-devel-version.rpm (C include files and libraries for developers)
  • php-mysql-version.rpm (For accessing MySQL database from php)
Install: rpm -ivh mysql-version.rpm mysql-server-version.rpm mysqlclient9-version.rpm
Check if installed: rpm -q mysql mysql-server mysqlclient9
The examples on this page used mySQL 3.23.58 which is used in Red Hat 7, 8, 9 and Fedora Core 1, 2, 3.
Also see YoLinux.com systems administration - using RPM to set GPG signatures and install RPM packages.

Installing MySQL.com RPM packages: If instaling newer versions of MySQL from RPM packages obtained from MySQL.com, you must first import and register their public GPG key:

  1. Download public key named build@mysql.com from http://www.keyserver.net/ with one of two methods:
    • wget --output-document=pubkey_mysql.asc http://keyserver.veridis.com:11371/export?id=-8326718950139043339
      (Saves key 0x5072E1F5 as file pubkey_mysql.asc)
    • gpg --keyserver keyserver.veridis.com --recv-key 5072e1f5
      gpg --export -a 5072e1f5 > pubkey_mysql.asc
  2. Import key: rpm --import pubkey_mysql.asc

[Potential Pitfall]: Your system should have a host name other than the default "localhost". Give your systems a host name if you get the following installation error:
ERROR: 1062  Duplicate entry 'localhost-root' for key 1
ERROR: 1062 Duplicate entry 'localhost-' for key 1
Use the command hostname to give your system a hostname and also set in the configuration file /etc/sysconfig/network

Ubuntu / Debian package installation:

  • apt-get install mysql-client
  • apt-get install mysql-server


Start the database:

Start the database: /etc/rc.d/init.d/mysqld start
(The script will run /usr/bin/mysql_install_db to create a default database in /var/lib/mysql/mysql/ if the mysql init script has never been run before. The install script will not be run again as long as the default database directory exists.)
The database executes as user mysqld and group mysqld.

Notes:

  • Init script will create and initialize the database with the command: /usr/bin/mysql_install_db
    Creates system tables in /var/lib/mysql/mysql/
    Only executes the first time the MySQL init script is run. One may also initialize the database manually using this command.
  • Files for databases located in: /var/lib/mysql/
  • Default config file installed by RPM: /etc/my.cnf
    (Ubuntu: /etc/mysql/my.cnf)
    [mysqld]
    datadir=/var/lib/mysql
    socket=/var/lib/mysql/mysql.sock

    [mysql.server]
    user=mysql
    basedir=/var/lib

    [safe_mysqld]
    err-log=/var/log/mysqld.log
    pid-file=/var/run/mysqld/mysqld.pid

Post installation:

  1. Admin user id: root
    Default password: blank

    The first task is to assign a password:

    [prompt]$ mysqladmin -u root password 'new-password'
                  
    Note: the following SQL commands will also work:
    mysql> USE mysql;
    mysql> UPDATE user SET Password=PASSWORD('new-password') WHERE user='root'; mysql> FLUSH PRIVILEGES;
  2. Create a database: (Creates directory /var/lib/mysql/bedrock)
    [prompt]$ mysqladmin -h localhost -u root -ppassword create bedrock
    (or use SQL command: CREATE DATABASE bedrock;)
    Show all mysql databases: mysqlshow -u root -ppassword

  3. Add tables, data, etc:
    Connect to database and issue the following SQL commands:
    [prompt]$ mysql -h localhost -u root -ppassword
    ...
    mysql> show databases;             -- List all databases in MySQL.
    +----------+
    | Database |
    +----------+
    | bedrock  |
    | mysql    |
    | test     |
    +----------+
    mysql> use bedrock;     -- Specify database to connect to. Also refers to path: /var/lib/mysql/bedrock
    mysql> create table employee (Name char(20),Dept char(20),jobTitle char(20));
    mysql> DESCRIBE employee; -- View table just created. Same as "show columns from employee;" +----------+----------+------+-----+---------+-------+ | Field | Type | Null | Key | Default | Extra | +----------+----------+------+-----+---------+-------+ | Name | char(20) | YES | | NULL | | | Dept | char(20) | YES | | NULL | | | jobTitle | char(20) | YES | | NULL | | +----------+----------+------+-----+---------+-------+ 3 rows in set (0.03 sec) mysql> show tables;
    +-------------------+
    | Tables_in_bedrock |
    +-------------------+
    | employee |
    +-------------------+

    mysql> INSERT INTO employee VALUES ('Fred Flinstone','Quarry Worker','Rock Digger');
    mysql> INSERT INTO employee VALUES ('Wilma Flinstone','Finance','Analyst');
    mysql> INSERT into employee values ('Barney Rubble','Sales','Neighbor');
    mysql> INSERT INTO employee VALUES ('Betty Rubble','IT','Neighbor');
    Note: Data type used was CHAR. Other data types include:
    • CHAR(M) : Fixed length string. Always stores M characters whether it is holding 2 or 20 characters. Where M can range 1 to 255 characters.
    • VARCHAR(M) : Variable length. Stores only the string. If M is defined to be 200 but the string is 20 characters long, only 20 characters are stored. Slower than CHAR.
    • INT : Ranging from -2147483648 to 2147483647 or unsigned 0 to 4294967295
    • FLOAT(M,N) : FLOAT(4,2) - Four digits total of which 2 are after the decimal. i.e. 12.34 Values are rounded to fit format if they are too large.
    • DATE, TEXT, BLOB, SET, ENUM

  4. Add a user. Use the MySQL SQL console to enter SQL commands. The command mysql with the correct login/password will connect you to the database. The admin tables are stored in the database "mysql".
    [prompt]$ mysql -h localhost -u root -ppassword
    Welcome to the MySQL monitor.  Commands end with ; or \g.
    Your MySQL connection id is 1 to server version: 3.23.41
    
    Type 'help;' or '\h' for help. Type '\c' to clear the buffer.
    
    mysql> USE mysql;
    mysql> SHOW TABLES; +-----------------+ | Tables_in_mysql | +-----------------+ | columns_priv | | db | | func | | host | | tables_priv | | user | +-----------------+ mysql> INSERT INTO user (Host, User, Password, Select_priv) VALUES ('', 'Dude1', password('supersecret'), 'Y'); mysql> FLUSH PRIVILEGES; -- Required each time one makes a change to the GRANT table mysql> GRANT ALL PRIVILEGES ON bedrock.* TO Dude1; mysql> FLUSH PRIVILEGES; -- Required each time one makes a change to the GRANT table mysql> quit
    Note:
    • There is NO space between the -p and the password! You can omit the password and you will be prompted for it.
    • The SQL flush command is equivalent to issuing the command:
      [prompt]$ mysqladmin reload

  5. Test the database:
    mysql> SELECT * from employee;
    +-----------------+---------------+-------------+
    | Name            | Dept          | jobTitle    |
    +-----------------+---------------+-------------+
    | Fred Flinstone  | Quarry Worker | Rock Digger |
    | Wilma Flinstone | Finance       | Analyst     |
    | Barney Rubble   | Sales         | Neighbor    |
    | Betty Rubble    | IT            | Neighbor    |
    +-----------------+---------------+-------------+
    1 row in set (0.00 sec)
    
    mysql> SELECT name FROM employee WHERE dept='Sales';
    +---------------+
    | name          |
    +---------------+
    | Barney Rubble |
    +---------------+
    1 row in set (0.00 sec)
                  

  6. Quit from the SQL shell:
    [prompt]$ quit

  7. Shutting down the database:
    [prompt]$ mysqladmin -u root -ppassword shutdown       - PREFERRED
    OR
    [prompt]$ /etc/rc.d/init.d/mysqld stop
    OR [prompt]$ service mysqld stop

Documentation in /usr/share/doc/mysql-3.23.41/ (local file)


Users and Security:

Create a database user:

     mysql> CREATE USER david@'localhost' IDENTIFIED BY 'password';
          

or generate a user by adding them to the user table directly:
     [prompt]$ mysql -h localhost -u root -p 
     mysql> use mysql;
     mysql> INSERT INTO user (Host,User,Password) VALUES('localhost','david',PASSWORD('supersecret'));
          
Note that the user is defined in the "user" mysql table.

Assign user privileges:

Security and database access is controlled by the GRANT tables. Access to connect to the database and access to process the transaction (table and column access, etc.) are both required. Privileges are searched in the following order:
  1. user table
  2. db and host table
  3. tables_priv
  4. columns_priv

Use the user table to grant connection privileges to database by a user (host, user name and password). Grant database and table access for transaction access. i.e. grant "SELECT", "UPDATE", "CREATE", "DELETE", "ALTER" etc. permission for database, table, field (columns) or database server access.

Access can be granted by network permissions: GRANT ALL PRIVILEGES on bedrock.* to david@'192.168.10.0/255.255.255.0';
This grants access from nodes 192.168.10.0 - 192.168.10.255. Or the network definitions can reference resolvable names: '%.domain.com'. The host definition of '%' or '' (null) refers to any host. (..according to the documentation. My experience is that in the mysql.user table use only '%' for "Host" to refer to any host.)

     mysql> GRANT ALL PRIVILEGES on bedrock.* to david@'%';
     mysql> FLUSH PRIVILEGES;
          
or (be specific)
     mysql> GRANT SELECT,INSERT,UPDATE,DELETE on bedrock.* to david@'%' identified by 'david';
     mysql> FLUSH PRIVILEGES;
          
or (more promiscuous - global privileges rather than database specific)
     mysql> GRANT ALL PRIVILEGES on *.* to david@'%' identified by 'david';
     mysql> FLUSH PRIVILEGES;
          
or (be specific by direct assignment in the mysql "Db" table:)
     mysql> use mysql;
     mysql> INSERT INTO db (Host,Db,User,Select_priv,Insert_priv) VALUES('localhost','bedrock','david','Y,'Y');
     mysql> FLUSH PRIVILEGES;
          
Note that database specific privileges (eg. Select_priv, Insert_priv, etc) are defined in the "db" mysql table. The mysql "user" table can assign the same (Select_priv, Insert_priv, etc) but global privileges (usually all default to 'N').

Show privileges: SHOW GRANTS FOR Dude2@'%';

Network security: Use firewall rules (ipchains or iptables) to block internet access to port 3306. (default port used by MySQL)

Note: I have found that when adding access from "anywhere" ('%'), the MySQL database table 'user' requires two entries, 'localhost' and '%'. Also, it is typically safer to allow more privileges to those with 'localhost' access than to users from '%' ("anywhere").

Passwords and connecting to the databse:

  • Connect: [prompt]$ mysql -h host_name -u user_name -ppassword
  • Using default blank password: [prompt]$ mysql -h localhost -u root -p
    If a password is required, you will be prompted. Note, blank passwords are a security hole which has already lead to one mySQL internet worm. Change any default blank passwords.
  • Delete null/blank users: DELETE FROM user WHERE User = '';
  • Beware of open access permissions from hosts '%': SELECT * FROM db WHERE Host = '%';
  • Change a password:
        [prompt]$ mysqladmin -u root -p password new-password
        

    You will be prompted to enter the old root password to complete this command.
    or:
        [prompt]$ mysqladmin -u root -pold-password password new-password
        

    or:
        mysql> SET PASSWORD FOR root@'localhost' = PASSWORD('supersecret');
    mysql> FLUSH PRIVILEGES;
  • As an added security precaution it is wise to delete any user id not used. i.e. any defaults generated for demonstration purposes.
  • Note that the default port used by MySQL is 3306. This can be protected with firewall rules. See the YoLinux IpTables tutorial.

Debian/Ubuntu upgrades: Note that the Debian/Ubuntu distribution will have an additional file /etc/mysql/debian.conf. This file holds a password for the user "debian-sys-maint" which is used by the install tool dpkg to perform database upgrades. This can also be used in emergencies if you forget the root password. It is also a security hole if the file is available to others.

[Potential Pitfall]: It is very easy to make mistakes which get entered into important tables. If you enter the command twice you may have one incorrect and one correct entry. Look at the table data after a mistake to see what happened in case it needs to be fixed.
Example:

mysql> USE mysql;
mysql> SELECT User,Password,Host from user;
+-------+------------------+------------+
| User | Password | Host |
+-------+------------------+------------+
| root | 99a1544eb571ad63 | localhost |
| | | localhost |
| Dude1 | 81a10dba5f6f2144 | |
| Dude1 | | |
| Dude2 | 92b10dba6f7f3155 | % |
+-------+------------------+------------+
5 rows in set (0.00 sec)
mysql> DELETE FROM user WHERE User='' AND Host='localhost';
mysql> DELETE FROM user WHERE User='Dude1' AND Password='';
mysql> FLUSH PRIVILEGES;
mysql> QUIT
User entries may also be found in the table mysql.db.
mysql> DELETE FROM db WHERE User='Dude3' AND Host='localhost';

[Potential Pitfall]: Any changes (UPDATE) to the user table will require a "FLUSH PRIVILEGES" before the changes will be effective.

mysql> UPDATE user SET Host='%' WHERE User='Dude2';
mysql> FLUSH PRIVILEGES;
This will allow a connection with mysql client from any host:
[prompt]$ mysql -u Dude2 -ppassword -h node.your-domain.com


MySQL root password recovery:

  1. As Linux system root user stop the database process: /etc/init.d/mysql stop
    (or: service mysql stop)
  2. Start MySQL in safe mode and skip the use of the "grant tables": /usr/bin/mysqld_safe --user=mysql --socket=/var/lib/mysql/mysql.sock --pid-file=/var/run/mysqld/mysqld.pid --datadir=/var/lib/mysql --skip-grant-tables --skip-networking &
  3. Reset the MySQL root password: mysqladmin -u root flush-privileges password newpassword
  4. Stop MySQL running in safe mode: kill `cat /var/run/mysqld/mysqld.pid`
  5. Start MySQL: /etc/init.d/mysql start
  6. The new MySQL root password can now be used: mysql -u root -p
    Respond with the password: newpassword


Disabling networking:

If your configuration is a web server interacting with a mySQL database running on the same "localhost" then one may turn off network access to tighten security. Edit shell script:
  • /usr/bin/safe_mysqld (Fedora Core 3)
  • /usr/bin/mysqld_safe (Red Hat Enterprise Linux 4 - MySQL 5.0)
..
...
if test -z "$args"
then
$NOHUP_NICENESS $ledir/$MYSQLD $defaults --basedir=$MY_BASEDIR_VERSION \
--datadir=$DATADIR $USER_OPTION --pid-file=$pid_file \
--skip-networking --skip-locking >> $err_log 2>&1
else
eval "$NOHUP_NICENESS $ledir/$MYSQLD $defaults --basedir=$MY_BASEDIR_VERSION \
--datadir=$DATADIR $USER_OPTION --pid-file=$pid_file \
--skip-networking --skip-locking $args >> $err_log 2>&1"
fi
...
..
Add the flag "--skip-networking" marked in bold.

Mysql 5.0 configuration: Networking is disabled by default on the default Red Hat and Ubuntu installation.

Red Hat/CentOS: To enable remote database access, add the "bind-address" with the public IP address to the file: /etc/my.cnf. To force local access only without remote access, set the "bind-address" to 127.0.0.1
[mysqld]
datadir=/var/lib/mysql
socket=/var/lib/mysql/mysql.sock
user=mysql
bind-address=127.0.0.1
          
Restart the database after making changes.
Ubuntu: To enable remote database access, comment out (or remove) the following line with a "#" in the file: /etc/mysql/my.cnf
...
...

bind-address           = 127.0.0.1

...
...
          
Restart the database after making changes.

A firewall rule can further restrict access to a single server (eg web server at 192.168.1.13):
/sbin/iptables -A INPUT -i eth0 -s 192.168.1.13 -p tcp --destination-port 3306 -j ACCEPT
or LAN only access:
/sbin/iptables -A INPUT -i eth0 -s 192.168.1.0/24 -p tcp --destination-port 3306 -j ACCEPT


MySQL Admin Commands:

  • Statistics: [prompt]$ mysqladmin version
  • List database environment: [prompt]$ mysqladmin variables
  • Show if database is running: [prompt]$ mysqladmin ping
  • Show databases available:
    [prompt]$ mysqlshow
    
    +-----------+
    | Databases |
    +-----------+
    | bedrock   |
    | mysql     |
    | test      |
    +-----------+
    
    OR
    mysql> SHOW DATABASES;
  • Delete database: mysql> drop database bedrock;
  • Show list of active threads in server:
    [prompt]$ mysqladmin -h localhost -u root -p processlist

    +----+------+-----------+----+---------+------+-------+------------------+
    | Id | User | Host | db | Command | Time | State | Info |
    +----+------+-----------+----+---------+------+-------+------------------+
    | 15 | root | localhost | | Query | 0 | | show processlist |
    +----+------+-----------+----+---------+------+-------+------------------+
  • Delete a database: [prompt]$ mysqladmin drop database-name
  • Execute SQL from Linux command line interface:
    [prompt]$ mysql -h localhost -u root -p -e "select host,db,user from db" mysql
  • Execute SQL command file from Linux command line interface:
    [prompt]$ mysql -h localhost -u root -p database-name < text-file-with-sql-statements.sql
  • Loadtest (benchmark) the system:
    [prompt]$ cd sql-bench
    [prompt]$ run-all-tests
    or [prompt]$ mysql -vvf test < ./tests/auto_increment.tst


Sample SQL:

SQL requests are either administrative or data-related. The following are sample SQL segments and are not necessarily pertinent to the previous example:

Create and use a new database named "bedrock":

mysql> CREATE DATABASE bedrock;   -- Comments follow a double dash
mysql> USE bedrock;

Create and populate table with data:

mysql> CREATE TABLE retired_employee (
                    Name char(20) DEFAULT '' NOT NULL,
                    Dept char(10) DEFAULT '' NOT NULL,
                    JobTitle char(20),
                    UNIQUE name_dept (Name,Dept)
                    );
mysql> CREATE UNIQUE index name_dept on employee (name,dept); -- avoids duplicate keys
mysql> INSERT INTO employee VALUES ("Jane Smith","Sales","Customer Rep");
mysql> INSERT INTO employee VALUES ('Jane Smith','Sales','Account Manager');
mysql> INSERT INTO employee VALUES ('Jane Smith','Engineerin','Manager');
mysql> UPDATE employee SET dept='HR' WHERE name='Jane Smith';
mysql> CREATE TABLE pet (
                 name VARCHAR(20), 
                 owner VARCHAR(20), 
                 species VARCHAR(20), 
                 sex CHAR(1), 
                 birth DATE, 
                 death DATE);

Add constraints to a table:

-- Use "auto_increment" integer column:
mysql> ALTER TABLE employee ADD EmpId INT NOT NULL AUTO_INCREMENT PRIMARY KEY; 
mysql> ALTER TABLE employee DROP INDEX name_dept;  -- get rid of index
mysql> 

Interrogate an existing database:

mysql> SHOW DATABASES;
mysql> USE bedrock;
mysql> SELECT DATABASE();  -- returns current database. eg. bedrock
mysql> SELECT VERSION();
mysql> SELECT NOW();
mysql> SELECT USER();
mysql> SHOW TABLES;
mysql> DESC employee;
mysql> SHOW CREATE TABLE employee;  -- show command used to generate table
mysql> SHOW INDEX FROM employee;
mysql> SELECT DISTINCT dept FROM  bedrock;
mysql> SELECT * FROM  bedrock WHERE Name  LIKE "B%y";  -- "%" match any char: Gives Betty and Barney
mysql> SELECT * FROM  bedrock WHERE Name LIKE "B___y";  -- "_" match space: Gives Betty but not Barney
mysql> SELECT * FROM  bedrock WHERE Name RLIKE "^Betty$";  -- "^" match beginning. "$" to denote end of string
mysql> SELECT COUNT(*) FROM employee;  -- Number of records returned
mysql> SELECT Name, COUNT(*) FROM employee WHERE Name LIKE "B%y";  -- Return Names and number of records returned
mysql> SELECT * FROM pet WHERE species = "snake" OR species = "bird";
mysql> SELECT * FROM pet WHERE species = "dog" AND sex = "f";
mysql> SELECT * FROM pet WHERE birth >= "1998-1-1";
mysql> SELECT name, birth FROM pet ORDER BY birth DESC;
mysql> SELECT * FROM pet WHERE name LIKE "b%";
mysql> SELECT * FROM pet WHERE name REGEXP "^b";
mysql> SELECT species, COUNT(*) FROM pet GROUP BY species;
mysql> SELECT MAX(article) AS article FROM shop;
mysql> SELECT * FROM employee WHERE name LIKE "%Sm%";
mysql> SELECT * FROM employee WHERE name REGEXP "^Ja";

Database cleanup:

mysql> DROP TABLE employee;
mysql> DROP DATABASE bedrock;
See section 3 of MySQL manual for more examples.
Tip: Execute a shell command from the MySQL client interface, use either option:
  • system ls -l
    OR
  • \! ls -l
Example: execute the "ls" command to list files from the MySQL client.


Loading Data into the MySQL database:

Loading a SQL file into MySQL:

Import SQL file from MySQL client command line:
  • mysql> source file.sql
    OR
  • mysql> \. file.sql
The SQL file may have schema generation statements like CREATE TABLE ... or data load statements like INSERT INTO ... . The statements in the SQL file will be executed as if they were being specified at the MySQL client command line interface.


One may import data into the MySQL database from SQL files or "load" data from CSV or tab delimited files using the LOAD command:

Loading CSV or tab delimeted files into MySQL:

"LOAD DATA LOCAL INFILE" vs "LOAD DATA INFILE": The term "LOCAL" pertains to whether the file is local to the MySQL client. Without the keyword "LOCAL", the datafile must reside on the same computer as the database server. The location of the client in this case would be irrelevant. The "LOAD DATA INFILE" has many file permission pitfalls and is thus trickey. In fact I have never been sucessful using this method with a user directory.

Load a tab delimited file into the database:

Command: LOAD DATA LOCAL INFILE 'file.dat' INTO TABLE employer;

Input tab delimited file: file.dat

Fred Flinstone  Quarry Worker   Rock Digger
Wilma Flinstone Finance Analyst 
Barney Rubble   Sales   Neighbor
Betty Rubble    IT      Neighbor
                
Note:
  • The number of tab delimeted fields MUST match the number and order of fields in the database.

Load a comma delimited file (CSV) into the database:

Command: LOAD DATA LOCAL INFILE "/tmp/TableData.csv" INTO TABLE employer FIELDS TERMINATED BY "," OPTIONALLY ENCLOSED BY """" LINES TERMINATED BY "\r\n" (Name, Dept, jobTitle);

Note:
  • MS/Windows generated files will have lines terminated by "\r\n".
  • Linux/Unix generated files will have lines terminated by "\n".
  • File locations on database server must be absolute path names, relative path or relative to the mysqld process owner's home directory (typically /var/lib/mysql/). File locations on the client may be fully qualified or relative to the current mysql client directory.
    • Fully qualified: /tmp/TableData.csv
    • Relative to current mysql client directory: ./TableData.csv
      (Verify current directory: mysql> \! pwd)
    • Database process owner home directory: TableData.csv
      (Actual: /var/lib/mysql/TableData.csv)
  • Text strings often are encapsulated by quotes so that the strings may contain a comma without representing a new field.

[Potential Pitfalls]:

  • ERROR 13 (HY000): Can't get stat of '/tmp/TableData.csv' (Errcode: 13)
    The fils is local and you have not specified the "LOCAL" directive.
  • ERROR 29 (HY000): File '/var/lib/mysql/test/TableData.csv' not found (Errcode: 2)
    Error from command LOAD DATA INFILE 'TableData.csv' INTO ... where the file is assumed to be read from the /database-process-home-directory/mysql-database-name/TableData.csv
    (Note: Database name "test" is being used.)
  • ERROR 1045 (28000): Access denied for user 'user1'@'%' (using password: YES)
    OR
    ERROR 2 (HY000): File '/tmp/TableData.csv' not found (Errcode: 2)
    Error from command LOAD DATA INFILE '/tmp/TableData.csv' INTO .... This is a common pitfall, trying to load a file located on the database server remotely from a client. Getting the file permissions correct is difficult. Avoid this method. Use the LOAD DATA LOCAL INFILE instead of the LOAD DATA INFILE method (it is so much easier).

Also look at the mysqlimport command.


Dump/Backup/Transfer Database:

The mysqldump command will read the mySQL database and generate a SQL command text file. This allows data to be migrated to other versions of mySQL (i.e. upgrade from typical Red Hat (RH7.x to FC3) mySQL release 3.23.58 to a more advanced mySQL 4.1 or 5.0) or to other SQL databases. SQL command file generated can create tables, insert data, ....

Option Description
-A
--all-databases
Dump all the databases.
-B
--databases
Dump the specified databases.
-h
--host=
Specify host to connect to.
-p
--password=
Specify password. If you do not specify a password, then you will be queried.
-u
--user=
Specify user. Defaults to current user logged in.
--opt Same as: --add-drop-table --add-locks --all --extended-insert --quick --lock-tables
--add-drop-table Add a "drop table" SQL statement before each "create" SQL statement.
--add-locks Add "lock" SQL statements around "insert" SQL statements.
-a
--all
Include all mySQL specific SQL "create" options.
-e
--extended-insert
Allows utilization of the new, much faster INSERT syntax. Database you are migrating to must support this notation.
-q
--quick
Don’t buffer query, dump directly to stdout.
-l
--lock-tables
Lock all tables for read.
-?
--help
Display command line options.

Examples:

  • Dump database to a file:
    • Dump specified database:
      mysqldump --opt database > db-dump-file.sql
    • Dump specified table in database:
      mysqldump --opt database table-name > db-dump-file.sql
    • Dump multiple databases:
      mysqldump --opt --databases database1 database2 database3 > db-dump-file.sql
    • Dump everything:
      mysqldump --opt --all-databases > total-db-dump-file.sql
      mysqldump -u user-id -h host-name --opt --all-databases > total-db-dump-file.sql
    [Potential Pitfall]: If you experience the following error:
    mysqldump: Got error: 1016: Can't open file: 'Database-Name' (errno: 145) when using LOCK TABLES
    Fix with the following command: mysqlcheck -r -u root -p Database-Name
  • Import dumped file:
    mysql database < db-dump-file.sql
  • Export from one database and import to another:
    • Transfer specifed database from one database to another:
      mysqldump --opt database | mysql --host=host-name -C database

Man Page:

Upgrading to 4.1:


Restore MySql Database:

Restore using dump generated by mysqldump above:

  • mysql -h host-name -u user-id -psupersecretpassword < total-db-dump-file.sql
  • mysql database-name -h host-name -u user-id -psupersecretpassword < db-dump-file.sql


System Notes:

Quiesce Database:

When using enterprise storage with "snapshot" capabilities (eg Netapp, HP, EMC, ...), note that a "snapshot" of a database with transaction locks is a "snapshot" of a database in an inconsitant state. One should quiesce the database, to halt further changes, before taking the snapshot so that you have a transactionally consistent backup of mysql.

Check Database Status:
Show process list (database activity):
mysql> SHOW PROCESSLIST;
+---------+-----------+-----------+------+---------+------+-------+------------------+
| Id      | User      | Host      | db   | Command | Time | State | Info             |
+---------+-----------+-----------+------+---------+------+-------+------------------+
| 1713762 | root      | localhost | NULL | Query   |    0 | NULL  | show processlist | 
| 1713939 | user4     | localhost | SF   | Sleep   |    0 |       | NULL             | 
+---------+-----------+-----------+------+---------+------+-------+------------------+
2 rows in set (0.00 sec)

Show the database status:
mysql> SHOW ENGINE INNODB STATUS\G
*************************** 1. row ***************************
Status: 
=====================================
130505  9:20:52 INNODB MONITOR OUTPUT
=====================================
Per second averages calculated from the last 51 seconds
----------
SEMAPHORES
----------
OS WAIT ARRAY INFO: reservation count 1084680, signal count 1069717
Mutex spin waits 0, rounds 1777219, OS waits 4374
RW-shared spins 2163653, OS waits 1078122; RW-excl spins 7932, OS waits 113
------------
TRANSACTIONS
------------
Trx id counter 0 2656185
Purge done for trx's n:o < 0 2652578 undo n:o < 0 0
History list length 9
Total number of lock structs in row lock hash table 0
LIST OF TRANSACTIONS FOR EACH SESSION:
---TRANSACTION 0 0, not started, process no 17024, OS thread id 1092143424
MySQL thread id 1713762, query id 24061088 localhost root
SHOW ENGINE INNODB STATUS
--------
FILE I/O
--------
I/O thread 0 state: waiting for i/o request (insert buffer thread)
I/O thread 1 state: waiting for i/o request (log thread)

...
...

Flush table transactions and lock: Closes all open tables and locks all tables for all databases with a global read lock.
mysql> FLUSH TABLES WITH READ LOCK;
Query OK, 0 rows affected (0.02 sec)
This will temporary make MySQL read only. It also requires LOCK TABLES privileges.

Database activity: One can then view database activity with the SQL command: SHOW PROCESSLIST;
If configured for replication in a master/slave cluster, the master node may have binary log files of changes for the slaves.
View status: SHOW MASTER STATUS/G
If backing up from a slave: SHOW SLAVE STATUS/G
Database activity should rapidly complete and when it has, this is the time to perform backups and snapshots.

XFS volume freeze: Note file system considerations (XFS): (after the "READ LOCK" has been applied and the database has been locked)
Freeze from further modification, an entire file system volume on which the MySQL data resides: SYSTEM xfs_freeze -f /var/lib/mysql;
The backlog of write activity will complete and further file system modification will be denied.
Perform backups now.
Unfreeze filesystem volume: SYSTEM xfs_freeze -u /var/lib/mysql;

Take database snapshot then unlock:
mysql> UNLOCK TABLES;
Query OK, 0 rows affected (0.00 sec)

[Potential Pitfall]: Ubuntu mysql 5.0 database migration - When migrating the mysql database by copying files from /var/lib/mysql/... and /etc/mysql/... from one system running Ubuntu 6.11 to 8.04, I got nebulous error message in /var/log/syslog. The root cause of the problem was apparmor. If turing off apparmor (/etc/init.d/apparmor stop) allows your database to start and function properly, then go fix your apparmor security rules in /etc/apparmor.d/usr.sbin.mysqld. Also note that you must use the newer script /etc/mysql/debian-start from release 8.04 after copying /etc/mysql/....

Note: Debian and Ubuntu distributions manage mysql package upgrades using a mysql user debian-sys-maint which has its information located in /etc/mysql/debian.cnf. If you ever forget your mysql root password, you can always get back into the mysql database using the user debian-sys-maint and its password held in /etc/mysql/debian.cnf.


Building MySql from source: (on Linux)

Prerequisites:

  • C compiler: 2.95.2 or later. (Check with the command: rpm -q gcc)
Compile and install: (as root)
  • Downloaded source from http://dev.mysql.com/downloads/mysql/4.1.html
  • Expand tar file: tar xzf mysql-4.1.16.tar.gz
  • cd mysql-4.1.16
  • ./configure --prefix=/opt/mysql --sysconfdir=/opt/etc --localstatedir=/opt/var/mysql --with-unix-socket-path=/opt/tmp/mysql.sock
    (Use the command ./configure --help to see all options.)
    This should create an installation which will not clobber an existing RPM mySQL installation.
  • make
  • make install
  • Create mysql config file: cp support-files/my-medium.cnf /opt/var/my.cnf
  • Create user/group mysql
    • Test if user/group mysql already exists: groups mysql
    • Create group: groupadd mysql
    • Create user: useradd -g mysql -M -r -d /opt/lib/mysql -s /sbin/nologin -c "MySQL Server" mysql
  • chown -R mysql:mysql /opt/var/mysql
Configure:
  • Install default database: /opt/mysql/bin/mysql_install_db --user=mysql
    Since this command is run as root, specify the --user option to operate command as user mysql.
    Creates help database with SQL script: /opt/mysql/share/mysql/fill_help_tables.sql
  • Start mySQL database: /opt/mysql/bin/mysqld_safe --user=mysql &
  • /opt/mysql/bin/mysqladmin -u root password 'new-password'
  • /opt/mysql/bin/mysqladmin -u root -h yoserver2 password 'new-password'
  • See tutorial above for use and administration.
  • Check defaults: (Defaults from config file: /opt/var/my.cnf)
    • /opt/mysql/bin/my_print_defaults --config-file=my client mysql
      --password=supersecret
      --port=3306
      --socket=/opt/tmp/mysql.sock
      --no-auto-rehash
          
    • /opt/mysql/bin/my_print_defaults --config-file=my client mysql mysql_install_db
      --datadir=/var/lib/mysql
      --socket=/var/lib/mysql/mysql.sock
      --password=supersecret --port=3306 --socket=/opt/tmp/mysql.sock --port=3306 --socket=/opt/tmp/mysql.sock --skip-locking --key_buffer=16M --max_allowed_packet=1M --table_cache=64 --sort_buffer_size=512K --net_buffer_length=8K --read_buffer_size=256K --read_rnd_buffer_size=512K --myisam_sort_buffer_size=8M --log-bin --server-id=1


Commands/Man pages:

  • isamchk - Check and repair of ISAM tables.
  • isamlog - Write info about whats in a nisam log file.
  • msql2mysql
  • my_print_defaults
  • myisamchk
  • myisamlog
  • myisampack
  • mysql - text-based client for mysqld, a SQL-based relational database daemon
  • mysql_config
  • mysql_convert_table_format
  • mysql_find_rows
  • mysql_fix_privilege_tables
  • mysql_install_db
  • mysql_setpermission
  • mysql_zap - a perl script used to kill processes
  • mysqlaccess - Create new users to mysql.
  • mysqlbinlog
  • mysqlbug
  • mysqlcheck
  • mysqld_multi - Used for managing several mysqld processes running in different UNIX sockets and TCP/IP ports.
  • mysqldump - text-based client for dumping or backing up mysql databases , tables and or data.
  • mysqldumpslow
  • mysqlhotcopy
  • mysqlimport
  • mysqlshow - Shows the structure of a mysql database (databases,tables and columns)
  • mysqltest
  • pack_isam
  • perror - used to display a description for a system error code, or an MyISAM/ISAM table handler error code.
  • replace - A utility program to replace changes strings in place in files or on the standard input.
  • resolve_stack_dump
  • resolveip
Server:
  • mysqladmin - A utility for performing administrative operations
  • safe_mysqld - The recommended way to start a mysqld daemon on Unix.


Admin GUI Tools:


If one would like to generate a GUI interface to the database, I would recommenda web form to a Java servlet back-end or use a JAVA GUI program and JDBC. See the YoLinux tutorial on accessing MySQL with JDBC in a Tomcat servlet example.


Links:


Book imageBooks:

book cover image "MySQL, Second edition"
by Paul DuBois
ISBN # 0735712123, New Riders Publishing

Amazon.com
book cover image "Managing and Using MySQL"
by George Reese, Randy Jay Yarger, Tim King
ISBN # 0596002114, O'Reilly

Amazon.com
book cover image "MySQL Cookbook"
by Paul DuBois
ISBN # 0596001452, O'Reilly

Amazon.com
book cover image "High Performance MySQL"
by Jeremy D. Zawodny, Derek J. Balling
ISBN # 0596003064, O'Reilly

Amazon.com
book cover image "The Definitive Guide to MySQL, Second Edition"
by Michael Kofler
ISBN # 1590591445, APress

Amazon.com
book cover image "MySQL Certification Study Guide"
by Paul Dubois, Stefan Hinz, Carsten Pedersen
ISBN # 0672326329, Sams

Amazon.com
   

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Copyright © 2002 - 2013 by Greg Ippolito