backup dir 

Define a backup dir:

BACKUP_DIR="/opt/backup/backup-$(date +%Y-%m-%d_%H-%M)"

Take the backup: 

mariadb-backup --backup --parallel=2 --safe-slave-backup --target-dir="$BACKUP_DIR"

Note: --parallel=2 is optional, it can be adjusted based on your system's capabilities.

prepare 

mariadb-backup --prepare --target-dir="$BACKUP_DIR"

Warning: Advised to run this, as it will ensure that the backup works and can be restored without any problems.

compress 

tar -cf -"${BACKUP_DIR##*/}" | zstd > "$BACKUP_DIR.tar.zst"

S3 

If you want to upload the backup compressed to S3, you can use the following command:

tar -cf -"${BACKUP_DIR##*/}" | s3m --pipe -x <s3 provider>/<bucket>/backup.tar

Note: Replace <s3 provider> and <bucket> with your actual S3 provider and bucket name, check the s3m documentation for more details.

script 

All together the script looks like this:

BACKUP_DIR="/opt/backup/backup-$(date +%Y-%m-%d_%H-%M)"
mariadb-backup --backup --parallel=2 --safe-slave-backup --target-dir="$BACKUP_DIR"
mariadb-backup --prepare --target-dir="$BACKUP_DIR"
tar -cf -"${BACKUP_DIR##*/}" | zstd > "$BACKUP_DIR.tar.zst"