Using MYSQLDUMP to backup a database
The output of the MYSQLDUMP command can be piped or redirected to any location you want. If you plan to backup your database, you can pipe the output to a sql file, which will contain the SQL statements to recreate and populate the database tables when you wish to restore your database.
A Simple Database Backup:
You can use mysqldump to create a simple backup of your database using the following syntax.
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 file to which the backup should be written.
If you want to specify the databases to backup, you can use the --databases parameter followed by the list of databases you would like to backup. Each database name has to be separated by at least one space when you type in the command.
mysqldump -u [user name] -p [password] --databases [db1] [db2] [db3] > backup.sql
all the databases in the server
mysqldump --all-databases> alldatabases.sql
mysqldump --no-data --databases [db1] [db2] [db3] > structurebackup.sql
compression on the Fly
Backups of databases take up a lot of space. You can compress the output of mysqldump to save valuable space while you're backing up your databases. Since mysqldump sends its output to the console, we can pipe the output through gzip or bzip2 and send the compressed dump to the backup file. Here's how you would do that with bzip2 and gzip respectively.
mysqldump --all-databases | bzip2 -c >databasebackup.sql.bz2 mysqldump --all-databases | gzip >databasebackup.sql.gz
A Shell Script for Automating Backups?
You can automate the backup process by making a small shell script which will create a daily backup file. How do you get cron to back up your database without overwriting the older backup? You can use a tiny shell script to add the date to your backup file. An example of a shell script you could use is shown below.
#!/bin/sh date=`date -I` mysqldump --all-databases | gzip > /var/backup/backup-$date.sql.gz
The resultant dump file will contain all the SQL statements needed to create the table and populate the table in a new database server. To backup your database 'Customers' with the username 'sadmin' and password 'pass21' to a file custback.sql, you would issue the command:
mysqldump -u sadmin -p pass21 Customers > custback.sql
You can also ask mysqldump to add a drop table command before every create command by using the option --add-drop-table. This option is useful if you would like to create a backup file which can rewrite an existing database without having to delete the older database manually first.
mysqldump --add-drop-table -u sadmin -p pass21 Customers > custback.sql
Backing up only specified tables
If you'd like restrict the backup to only certain tables of your database, you can also specify the tables you want to backup. Let's say that you want to backup only customer_master & customer_details from the Customers database, you do that by issuing
mysqldump --add-drop-table -u sadmin -p pass21 Customers customer_master customer_details> custback.sql
So the syntax for the command to issue is:
mysqldump -u [username] -p [password] [databasename] [table1 table2 ....]o [tables] - This is a list of tables to backup. Each table is separated by a space.
Now that you've got backups of your database, let's learn how to restore your backup in case your database goes down. Here's how you can restore your backed up database using the mysql command.
Restore using mysql
If you have to re-build your database from scratch, you can easily restore the mysqldump file by using the mysql command. This method is usually used to recreate or rebuild the database from scratch.
Here's how you would restore your custback.sql file to the Customers database.
mysql -u sadmin -p pass21 Customers < custback.sql
Easy isn't it ? Here's the general format you would follow:
mysql -u [username] -p [password] [database_to_restore] < [backupfile]
Now how about those zipped files? You can restore your zipped backup files by first uncompressing its contents and then sending it to mysql.
gunzip < custback.sql.sql.gz | mysql -u sadmin -p pass21 Customers
You can also combine two or more backup files to restore at the same time, using the cat command. Here's how you can do that.
cat backup1.sql backup.sql | mysql -u sadmin -p pass21
Moving Data Directly Between Databases
How would you like to replicate your present database to a new location? When you are shifting web hosts or database servers, you can directly copy data to the new database without having to create a database backup on your machine and restoring the same on the new server. mysql allows you to connect to a remote database server to run sql commands. Using this feature, we can pipe the output from mysqldump and ask mysql to connect to the remote database server to populate the new database. Let's say we want to recreate the Customers database on a new database server located at 126.96.36.199, we can run the following set of commands to replicate the present database at the new server.
mysqldump -u sadmin -p pass21 Customers | mysql --host=188.8.131.52 -C Customers