Automated MySQL Backup Script with Docker and Crontab

This article provides a step‑by‑step tutorial for creating an automated MySQL backup system on an AlmaLinux 8.x host where the MySQL server runs inside a Docker container.

Environment

Operating system: AlmaLinux 8.x

Database: MySQL running in Docker

Scripts directory: ~/scripts

Preparation – Create script directory

Log in to the master server: ssh [email protected]

Create the directory and enter it: mkdir -p ~/scripts cd ~/scripts

Verify permissions: ls -ld ~/scripts Expected output (example): drwxr-xr-x 2 dba dba 4096 May 25 10:00 /home/dba/scripts

Shell script – backup_mysql.sh

The script backs up all databases at 02:00 each day and retains the last 7 days of backups.

#!/bin/bash
# backup_mysql.sh – automatic MySQL master backup
# Environment: AlmaLinux + Docker
# Dependencies: docker, gzip, mysqldump

# ---- 1. Basic variables ----
CONTAINER_NAME="mysql-master"
BACKUP_DIR="/home/dba/scripts/backups"
RETENTION_DAYS=7
DATE=$(date +"%F_%H%M")

# ---- 2. Command checks ----
for cmd in docker mysqldump gzip; do
  command -v $cmd > /dev/null 2>&1
  if [ $? -ne 0 ]; then
    echo "Error: command $cmd not found, please install it and retry!"
    exit 1
  fi
done

# ---- 3. Create backup directory ----
mkdir -p "$BACKUP_DIR"
if [ $? -ne 0 ]; then
  echo "Error: failed to create directory $BACKUP_DIR!"
  exit 1
fi

# ---- 4. Perform backup ----
BACKUP_FILE="$BACKUP_DIR/mysql_backup_${DATE}.sql.gz"
echo "[$(date +"%F %T")] Starting backup: $BACKUP_FILE"

docker exec $CONTAINER_NAME \
    mysqldump -uroot -p'your_password' --all-databases \
    | gzip > "$BACKUP_FILE"

if [ $? -eq 0 ]; then
  echo "[$(date +"%F %T")] Backup completed!"
else
  echo "[$(date +"%F %T")] Backup failed!"
  exit 1
fi

# ---- 5. Clean old backups ----
echo "[$(date +"%F %T")] Cleaning backups older than $RETENTION_DAYS days"
find "$BACKUP_DIR" -type f -name "mysql_backup_*.sql.gz" -mtime +$RETENTION_DAYS -print -delete

echo "[$(date +"%F %T")] Cleanup finished!"

Crontab configuration

Open the crontab editor (recommended editors: vim or nano ) and add the following line at the end of the file:

02 * * * * /home/dba/scripts/backup_mysql.sh >> /home/dba/scripts/backup.log 2>&1

This schedules the script to run daily at 02:00 and appends both standard output and error output to backup.log .

Common error troubleshooting

Error Message

Cause & Solution

bash: backup_mysql.sh: command not found

Make the script executable (

chmod +x backup_mysql.sh

) or use the absolute path.

docker: command not found

Install Docker (

sudo dnf install docker

) and ensure it is in

PATH

.

mysqldump: command not found

Install MySQL client inside the container (

yum install -y mysql

).

permission denied

Adjust directory permissions (

chmod -R 755 ~/scripts

).

File not found

Use an absolute path in the crontab entry.

Advanced usage & notes

Email notification (append at script end): mail -s "MySQL Backup Report $(date +'%F')" [email protected] < backup.log

Master‑slave replication check via a separate check_replication.sh script using SHOW SLAVE STATUS .

Centralized log management – ship backup.log to a log server or ELK stack.

Security – avoid hard‑coding passwords; use .my.cnf or Docker secrets.

Summary

Script writing: variables, command checks, error exits, logging.

Scheduled execution: crontab configuration and log redirection.

Troubleshooting: command existence, absolute paths, permissions.

Environment dependencies: AlmaLinux, Docker, GNU tools.

Follow the example, adjust paths and credentials as needed, and your MySQL database will be backed up reliably every night.