The MySql - Administration

How to retrieve the mysql root password.
/root/.my.cnf

above file contains the password

Setting the password:

1. From Unix:
shell> mysql -u username -h hostname -p password
mysql> SET PASSWORD FOR username@localhost=PASSWORD('new_password');

2. Directly manipulate the privilege tables:
shell> mysql -u username -h host -u username -p
mysql> UPDATE user SET Password=PASSWORD('new_password') WHERE user='root';
mysql> FLUSH PRIVILEGES;

3. Using the mysqladmin command:
shell> mysqladmin -u username password new_password

In our case we were able to change password specifying host name along with user name:
shell> bin/myslqadmin u username h localhost


MySQL Permissions & Grant Tables

In order to add a new user or update user's privileges in mysql grant tables login to mysql as a root user.

There are two options: use GRANT/REVOKE command or manipulating the MySQL grant tables directly.
The preferred method is to use GRANT statements - more concise and less error-prone.

If you modify the grant tables manually (using INSERT, UPDATE, etc.), you should execute
a FLUSH PRIVILEGES statement to tell the server to reload the grant tables.

To remove user: mysql> delete from user where user='username';
mysql> FLUSH PRIVILEGES;


Examples adding a new user with different level of privileges:
dummy: A user who can connect without a password, but only from the local host.

mysql> GRANT USAGE ON *.* TO dummy@localhost;

myUser : A full superuser who can connect to the server from anywhere,
but who must use a password 'pass' to do so.
GRANT statements should be for both myUser@localhost and myUser@"%".
to prevent the anonymous user entry for localhost take precedence.

mysql> GRANT ALL PRIVILEGES ON *.* TO myUser@localhost
IDENTIFIED BY 'pass' WITH GRANT OPTION;
mysql> GRANT ALL PRIVILEGES ON *.* TO myUser@"%"
IDENTIFIED BY 'some_pass' WITH GRANT OPTION;

"%" - is a wildcard in mysql. If you are defining your DB table and in the 'host' field
enter '%', that means that any host can access that database (Of course, that host
must also have a valid db user).


admin: A user who can connect from localhost without a password and who is granted
the RELOAD and PROCESS administrative privileges.
No database-related privileges are granted.

mysql> GRANT RELOAD,PROCESS ON *.* TO admin@localhost;


Add a user that has full rights to his database only but cannot see other database:
mysql> GRANT USAGE ON *.* TO 'user'@'host' GRANT Select, Insert, Update, Delete,
Create, Drop ON `database`.* TO 'user'@'host' FLUSH PRIVELEGS;

The FILE privelege and WITH GRANT OPTION may not be the best way to include, it is
only in case of creating another superuser with full set of privileges or
giving privileges to load data using mysql command INLOAD DATA.


GRANT TABLE FIELDS EXPLANATION:
TABLE USER: Everything after "password" is a privelege granted with values 'Y' or 'N'.
This table controls individual user global access rights.

'host','user','password','select','insert','update','delete','index','alter'
,'create','drop','grant','reload','shutdown','process','file'

TABLE DB: This controls access of USERS to databases.

'host','db','user','select','insert','update','delete','index','alter',
'create','drop','grant'

TABLE HOST: This controls which HOSTS are allowed what global access rights.

'host','db','select','insert','update','delete','index','alter',
'create','drop','grant'


HOST, USER, and DB table are very closely connected - if an authorized USER
attempts an SQL request from an unauthorized HOST, it is denied.
If a request from an authorized HOST is not an authorized USER, it is denied.
If a globally authorized USER does not have rights to a certain DB, it is denied.



Backups in MySQL

Full backup of MySql databases:
1. shell> mysqldump --tab=/path/to/some/dir --opt --full
OR
2. shell> mysqlhotcopy database /path/to/some/dir
OR
3. simply copy all table files (`*.frm', `*.MYD', and `*.MYI' files)

For a SQL level backup of a table use SELECT INTO OUTFILE or BACKUP TABLE.

mysql> BACKUP TABLE tbl_name[,tbl_name...] TO '/path/to/backup/directory'
Copies to the backup directory the minimum number of table files needed to
restore the table, after flushing any buffered changes to disk.

RESTORE TABLE tbl_name[,tbl_name...] FROM '/path/to/backup/directory'
Restores the table(s) from the backup that was made with BACKUP TABLE.
Existing tables will not be overwritten; if you try to restore over an existing
table, you will get an error. Restoring will take longer than backing up due to
the need to rebuild the index. The more keys you have, the longer it will take.
Just as BACKUP TABLE, RESTORE TABLE currently works only for MyISAM tables.

Selective backups can be done with:
SELECT * INTO OUTFILE 'file_name' FROM tbl_name
and restore with:
LOAD DATA INFILE 'file_name' REPLACE ...
To avoid duplicate records, you need a PRIMARY KEY or a UNIQUE key in the table.
The REPLACE keyword causes old records to be replaced with new ones when a new
record duplicates an old record on a unique key value.

Monitoring tools

The myisamchk utility is used to get information, check, repair or optimise mysql database tables:
shell> myisamchk [options] tbl_name

With no options, myisamchk simply checks the table.

Some useful Options for myisamchk utility:

1. Print informational statistics about the table that is checked: -i or --information
2. Check only tables that have changed since the last check: -C or --check-only-changed
3. The recommended way to quickly check all tables:
myisamchk --silent --fast /path/to/datadir/*/*.MYI

To Start the server automatically at system startup time

The mysql.server and safe_mysqld scripts can be used to start/stop the server automatically.
shell> mysql.server start
shell> mysql.server stop

See mysql.server in the `share/mysql' directory or in the `support-files' directory of the MySQL source tree.
The mysql.server script understands the following options: datadir, basedir, and pid-file.

If your system uses `/etc/rc.local' to start external scripts, you should append the following to it:

/bin/sh -c 'cd /usr/local/mysql ; ./bin/safe_mysqld --user=mysql &'

The mysql.server script understands the following options: datadir, basedir, and pid-file.


Backing Up MySQL Database

MySQL database backup can be accomplished in two ways:

a) Copying the raw mysql database files &
b) Exporting tables to text files

Copying the MySQL database files

MySQL uses the same table format on different platforms, so it's possible to copy MySQL table and index files from one platform and use them on another without any difficulties (assuming, of course, that you're using the same version of MySQL on both platforms).

Exporting tables to text files

The MySQLDump is handy utility that can be used to quickly backup the MySQL Database to the text files. To use the MySQLDump utility it is required to logon to the System running the MySQL Databse. You can use Telnet to remotely logon to the system if you don't have the physical access to the machine.

The syntax for the command is as follows.
mysqldump -u [Username] -p [password] [databasename] > [backupfile.sql]
[username] - this is your database username
[password]- this is the password for your database
[databasename] - the name of your database
[backupfile.sql] - the filename for your database backup



a) Taking the full backup of all the tables including the data.
Use the following command to accomplish this:
mysqldump -u admin -p admin accounts > accounts.sql

b) Taking the backup of table structures only.
Use the following command to accomplish this:
mysqldump -u admin -p admin --no-data accounts > accounts.sql

c) Taking the backup data only.
Use the following command to accomplish this:
mysqldump -u admin -p admin --no-create-info accounts > accounts.sql

Restoring MySQL Database

Restoring the MySQL is very easy job. You can use the following to command to restore the accounts database from accounts.sql backup file.

mysql - u admin -p admin accounts < accounts.sql