Change from current user to root user

  $ sudo -s
 
Now change to `postgres` user

  $ su - postgres
  
Create a simple backup. (Optional, just for test)

  $ pg_dump -U postgres your_db_name | gzip > your_db_name_backup.gz
  
Now, Create a backup storage folder
  
  - If your are in postgres user mode, no need to type this command if you are already in root user mode.
  
    $ exit
  
  - Create a backup storage folder
  
    $ sudo mkdir -p /backups/postgresql
  
  - Provide the postgres user permissions to the directory
    
    $ sudo chown postgres /backups/postgresql
 
  - Change back to the postgres user mode to set a cronjob.
  
    $ su - postgres
  
  - Open crontab by running the command
  
    $ crontab -e
    
  - Add this line at the end, replacing db_name with the name of your database
    
    ```text
    0 0 * 0 0 pg_dump -U postgres your_db_name | gzip > /backups/postgresql/your_db_name_backup.gz
    ```
    
    
# Extended Solution

1. Switch back to root user.

  `$ sudo -s`
  
2. Create a new folder where the backups will be stored.

  `$ mkdir /home/ubuntu/backups`
  
3. Give permission to the postgres user of this folder.

  `$ chown postgres /home/ubuntu/backups`
  
4. Create a shell script `$ nano backup_script.sh` and put the config below:
  
  `
  # Database name
  db_name=your_db_name
  # Backup storage directory 
  backupfolder=/home/ubuntu/backups
  # Number of days to store the backup 
  keep_day=10
  sqlfile=$backupfolder/your_db_name-database-$(date +%d-%m-%Y_%H-%M-%S).sql
  zipfile=$backupfolder/your_db_name-database-$(date +%d-%m-%Y_%H-%M-%S).zip

  #create backup folder
  mkdir -p $backupfolder
  # Create a backup
  if pg_dump $db_name > $sqlfile ; then
     echo 'Sql dump created'
  else
     echo 'pg_dump return non-zero code'
     exit
  fi
  # Compress backup 
  if gzip -c $sqlfile > $zipfile; then
     echo 'The backup was successfully compressed'
  else
     echo 'Error compressing backup'
     exit
  fi
  rm $sqlfile

  # Delete old backups 
  find $backupfolder -mtime +$keep_day -delete
  
5. Give permission of the script to `postgres` user and make the shell script executable.

  `$ chown /home/ubuntu/backup_script.sh
   $ chmod +x backup_script.sh
   `
6. Now change back to the postgres user so that we can update our cron job to run the new script by removing previous one.

  `
  $ su - postgres
  $ crontab -e
  `
 
7. Replace the previous command with the new one.

  `0 0 * 0 0 /home/ubuntu/backup_script.sh`

8. Done..