Introduction#

Cron job is one of most common techniques used on every Unix / Linux.

Common Use Cases#

House keeping - Clean up the backup#

• Run every night to remove the daily backup tar ball

• Assumption:

  • The script file named housekeeping.sh.
  • The script sits inside folder bin which is under your user account.
  • All backup files have the .tar as extension.
  • The script will check the backup tar balls within the folder bacup, which is under your user account as well.
  • The script will remove the latest backup if total backup files are over 5.

• Cron Job setting -

# Replace the user_id with you actual user name
20 15 * * * <user_id> /home/<user_id>/bin/housekeeping 2>&1  | logger

• The script file

#!/bin/bash

# crontab config 

# 20 15 * * * /home/${USER}/bin/housekeeping 2>&1 

# script location: /home/$(USER}/bin
# log file location: /home/$(USER}/log

logfile=/home/${USER}/log/housekeeping.log;
backup_dir=/home/${USER}/data/backups

# Log the start time
echo $(date)>> $logfile;

fln=$(($(find ${backup_dir} -type f -name "*.tar" | egrep -i ".tar" | wc -l)+0));

# Log the number of files 
echo $fln>>$logfile;

if [[ $fln -ge 6 ]]; then
  for t in $(find ${backup_dir} -type f -name "*.tar" | sort | egrep -m1 ".tar");
  do
    rm -rf   $t;
    # Log the removed file
    echo "remove $t" >> $logfile;
  done;
fi;

Backup the database#

Backup the MySql database nightly#

• The database backup dump will be stored into the folder named after the brand name, e.g. the folder facebook for Facebook

• The script of backup backup.sh

  
  # Every Backup directory has file named ENVIRONMENT
  # 
  # ENVIRONMENT contains the setting like db, server, etc.
  #
  #    DB_HOST=your_database_host_server
  #    DATABASE=the_target_database
  #    DB_USER=db_login_id
  #    DB_PASSWORD=db_password
  #    BACKUPS_TO_KEEP=5
  #
  
  
  # THIS SCRIPT MAY ONLY BE RUN ONCE EACH DAY
  # Usge:
  #   ./backup.sh facebook 
  #
  [[ -z "$1" ]] && echo "Must run script with brand name, which has matching folder in /var/backup/" && exit 1
  
  BACKUP_DIR=/var/backup/${1}
  source ${BACKUP_DIR}/ENVIRONMENT
  
  LATEST_DUMP_TARBALL=latest-dump.tgz
  DATE=$(date +%d-%m-%Y) # dd-mm-yyyy
  LATEST_BACKUP_DIR=${BACKUP_DIR}/${DATE}
  
  echo "$(date): Beginning backup of ${DATABASE} on ${DB_HOST}"
  mkdir -p ${LATEST_BACKUP_DIR}
  cd ${LATEST_BACKUP_DIR}
  START=$(date +%s)
  
  # Set procedure definer to ussadmin
  SQL="UPDATE mysql.proc p \
  SET definer = '${DB_USER}@%' \
  WHERE db = '${DATABASE}' \
  AND definer <> '${DB_USER}@%';"
  
  mysql -h ${DB_HOST} -P 3306 ${DATABASE} -u ${DB_USER} -p${DB_PASSWORD} -e"${SQL}"
  
  mysqldump -h ${DB_HOST} -P 3306 ${DATABASE} \
  --routines \
  --lock-tables=false \
  -u ${DB_USER} -p${DB_PASSWORD} > ./dump.sql
  
  EXPORT_RESULT=$?
  
  END=$(date +%s)
  echo "Export duration: $(( $END - $START ))s"
  
  echo "Gzipping dump file into tarball"
  
  START=$(date +%s)
  tar czf dump.tgz dump.sql
  [[ $? ]] &&  rm -f dump.sql
  END=$(date +%s)
  
  echo "Gzipping duration: $(( $END - $START ))s"
  
  echo "Creating ${BACKUP_DIR}/${LATEST_DUMP_TARBALL}"
  
  if [[ ${EXPORT_RESULT} ]]; then
  
      if [[ -f ${BACKUP_DIR}/${LATEST_DUMP_TARBALL} ]]; then
          rm --force ${BACKUP_DIR}/${LATEST_DUMP_TARBALL};
      fi
  
      ln -s ${LATEST_BACKUP_DIR}/dump.tgz ${BACKUP_DIR}/${LATEST_DUMP_TARBALL};
  
  else
      echo "Export operation did not return 0, skipping symlink update"
  fi
  
  echo "$(date): Completed backup for ${DATABASE} on ${DB_HOST}"