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How to Back Up and Restore MySQL Databases with Mysqldump


 wild
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Mysqldump Command Syntax 

Before going into how to use the mysqldump command, let’s start by reviewing the basic syntax.

The mysqldump utility expressions take the following form:

mysqldump [options] > file.sql

  • options - The mysqldump options
  • file.sql - The dump (backup) file

To use the mysqldump command the MySQL server must be accessible and running.

Backup a Single MySQL Database

The most common use case of the mysqldump tool is to backup a single database.

For example, to create a backup of the database named database_name using the user root and save it to a file named database_name.sql you would run the following command:

mysqldump -u root -p database_name > database_name.sql

You will be prompted to enter the root password. After successful authentication, the dump process will start. Depending on the database size, the process can take some time.

If you are logged in as the same user that you are using to perform the export and that the user does not require a password, you can omit the -u and -p options:

mysqldump database_name > database_name.sql

Backup Multiple MySQL Databases

To backup multiple MySQL databases with one command you need to use the --database option followed by the list of databases you want to backup. Each database name must be separated by space.

mysqldump -u root -p --databases database_name_a database_name_b > databases_a_b.sql

The command above will create a dump file containing both databases.

Backup All MySQL Databases

Use the --all-databases option to back up all the MySQL databases:

mysqldump -u root -p --all-databases > all_databases.sql

Same as with the previous example the command above will create a single dump file containing all the databases.

Backup all MySQL databases to separate files

The mysqldump utility doesn’t provide an option to backup all databases to separate files but we easily achieve that with a simple bash FOR loop :

for DB in $(mysql -e 'show databases' -s --skip-column-names); do
    mysqldump $DB > "$DB.sql";
done

The command above will create a separate dump file for each database using the database name as the filename.

Create a Compressed MySQL Database Backup

If the database size is very large it is a good idea to compress the output. To do that simply pipe the output to the gzip utility, and redirect it to a file as shown below:

mysqldump database_name | gzip > database_name.sql.gz

Create a Backup with Timestamp

If you want to keep more than one backup in the same location, then you can add the current date to the backup filename:

 

mysqldump  database_name > database_name-$(date +%Y%m%d).sql

The command above will create a file with the following format database_name-20180617.sql

Restoring a MySQL dump

You can restore a MySQL dump using the mysql tool. The command general syntax is as follows:

mysql  database_name < file.sql

In most cases you’ll need to create a database to import into. If the database already exists, first you need to delete it.

In the following example the first command will create a database named database_name and then it will import the dump database_name.sql into it:

mysql -u root -p -e "create database database_name";mysql -u root -p database_name < database_name.sql

Restore a Single MySQL Database from a Full MySQL Dump

If you backed up all your databases using the -all-databases option and you want to restore a single database from a backup file which contains multiple databases use the --one-database option as shown below:

mysql --one-database database_name < all_databases.sql

Export and Import a MySQL Database in One Command

Instead of creating a dump file from one database and then import the backup into another MySQL database you can use the following one-liner:

mysqldump -u root -p database_name | mysql -h remote_host -u root -p remote_database_name

The command above will pipe the output to a mysql client on the remote host and it will import it into a database named remote_database_name. Before running the command, make sure the database already exists on the remote server.

Automate Backups with Cron

Automating the process of backing up the databases is as simple as creating a cron job what will run the mysqldump command at specified time.

To set up automated backups of a MySQL database using cronjob, follow the steps below:

  1. Create a file named .my.cnf in your user home directory:

    sudo nano ~/.my.cnf

    Copy and paste the following text into the .my.cnf file.

    [client]
    user = dbuser
    password = dbpasswd

    Do not forget to replace dbuser and dbpasswdwith the database user and user’s password.

  2. Restrict permissions of the credentials file so that only your user has access to it:

    chmod 600 ~/.my.cnf
  3. Create a directory to store the backups:

    mkdir ~/db_backups
  4. Open your user crontab file:

    crontab -e

    Add the following cron job that will create a backup of a database name mydb every day at 3am:

    0 3 * * * /usr/bin/mysqldump -u dbuser mydb > /home/username/db_backups/mydb-$(date +\%Y\%m\%d).sql

    Do not forget to replace username with your actual user name. We’re also escaping the percent-signs (%), because they have special meaning in crontab.

You can also create another cronjob to delete any backups older than 30 days:

find /path/to/backups -type f -name "*.sql" -mtime +30 -delete

Of course, you need to adjust the command according to your backup location and file names. 


   
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