How to backup Docker on CentOS

Guide to backup data of Docker containers under CentOS

This article introduces two methods to use Docker to backup data on CentOS systems: running container data backup and Docker image backup.

1. Backup of container data during operation

1. Create a backup directory: Create a directory on the server to store backup files, for example:

    mkdir -p /home/docker/mysql/data_back && chmod -R 777 /home/docker/mysql/data_back

2. Confirm the container ID: Use the following command to get the ID of the container named mysql :

    docker ps -aqf "name=mysql"

3. Create a backup script (backup.sh): Create a backup.sh script in the /home/docker/mysql/data_back directory and add the following content:

    #!/bin/bash
   # Get the container ID
   container_id=$(docker ps -aqf "name=mysql")
   echo "MySQL container ID: $container_id"
   
   # Check if the container exists if [ -z "$container_id" ]; then
       echo "No container named mysql was found!"
       exit 1
   fi
   
   # MySQL login information (please replace it with your actual information)
   MYSQL_USER="root"
   MYSQL_PASSWORD="your_password" # Please replace it with your MySQL passwordMYSQL_PORT="3306"
   
   # Whether to delete expired backups (true/false)
   expire_backup_delete="true"
   expire_days=7
   
   # Backup file storage path backup_location="/home/docker/mysql/data_back"
   
   # Backup timestamp backup_time=$(date %Y%m%d%H%M)
   backup_Ymd=$(date %Y-%m-%d)
   backup_dir="$backup_location/$backup_Ymd"
   
   # Get the database list (exclude system database)
   DATABASES=$(docker exec $container_id mysql -u$MYSQL_USER -p$MYSQL_PASSWORD -e 'SHOW DATABASES;' | grep -vE '^(Database|information_schema|performance_schema)$')
   echo "Database List: $DATABASES"
   
   # Backup database if [ -n "$DATABASES" ]; then
       mkdir -p "$backup_dir"
       while read dbname; do
           echo "Start backup database: $dbname..."
           docker exec $container_id mysqldump --defaults-extra-file=/etc/mysql/conf.d -F -B --default-character-set=utf8 "$dbname" | gzip > "$backup_dir/bak-$dbname-$backup_time.sql.gz"
           if [ $? -eq 0 ]; then
               echo "Database $dbname backup was successful: $backup_dir/bak-$dbname-$backup_time.sql.gz"
           else
               echo "Database $dbname backup failed!"
           fi
       done 

4. Configure MySQL (my.cnf): Make sure there is the correct configuration file in the /etc/mysql/conf.d directory, and set the correct MySQL user and password. Be sure to replace your_password with your actual MySQL password.

5. Grant script execution permissions:

    chmod x /home/docker/mysql/data_back/backup.sh

6. Set timed tasks (crontab): Use crontab -e to edit crontab and add timed tasks, such as performing backups at 2 a.m. every day:

    <code>0 2 * * * /home/docker/mysql/data_back/backup.sh</code>

2. Docker image backup

1. Use the docker save command: Save the image as a tar package using the following command:

    docker save -o mycentos.tar mycentos_new:1.1

Please modify the parameters in the script according to the actual situation, such as container name, MySQL password, backup path and timing tasks. After the backup is completed, please properly store the backup files and regularly test the recovery process. Remember to check the integrity and effectiveness of backups regularly.

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