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You can perform logical backups of your database from Azure Database for PostgreSQL to azure storage accounts for long term retention. These backups can be restored to your on-prem environment or to another PostgreSQL instance on a Virtual Machine.


 


Follow the steps below to extract a backup from Azure Database for PostgreSQL to a Storage Account.


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In an nutshell, what we will need to do is the following:



  1. Use an existing VM or spin a Linux VM in the same region as the database (we use Ubuntu Server for this example).

  2. Mount your storage account as file share in the VM.

  3. Create a bash script that uses pg_dump to create a backup from your database.

  4. Schedule a task to run this script using crontab and to deallocate the VM when completed.

  5. Schedule the VM to start before the selected backup time using Logic Apps.


Prerequisites:



  1. Blob storage account with a File Share

  2. A Virtual Machine

  3. A Logic Apps instance.


 


Let’s break down each step.


 



  1. Spin up or use an existing Virtual Machine and configure it:



  1. Create a VM from the Azure portal. Refer to this QuickStart guide if needed.

  2. Start a remote session to your VM and install the following required packages:

    sudo apt install postgresql-client-10 # installs PostgreSQL client utilities
    sudo apt install cifs-utils # installs the Common Internet File System utilities
    curl -sL https://aka.ms/InstallAzureCLIDeb | sudo bash # installs Azure CLI


  3. If your PostgreSQL server is version 11 or above, please install the client tools with the following commands:

    sudo apt install wget ca-certificates
    wget --quiet -O - https://www.postgresql.org/media/keys/ACCC4CF8.asc | sudo apt-key add -
    sudo sh -c 'echo "deb http://apt.postgresql.org/pub/repos/apt/ `lsb_release -cs`-pgdg main" >> /etc/apt/sources.list.d/pgdg.list'
    sudo  apt update
    sudo apt-get install postgresql-client-11 #Or the required version above 10






    1.  


     



  1. Mount your storage account as a File Share.


 



  1. Create a File Share in your storage account

    1.  




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  1. If needed you can refer to this document on how to create an Azure File Share.



  2. Collect the following details from the Azure Portal: Resource Group, Storage Account Name and File Share Name.

  3. Log into your VM and declare the following variables:

    resourceGroupName="myResourceGroup"
    storageAccountName="myStorageAccount"
    fileShareName="myFileShare"
    mntPath="/home/azureuser/myfolder/"#File share needs to be mounted in the home directory rather than the mnt directory. Otherwise, folder will be deleted after VM deallocation.​


  4. Create a folder where the storage account will be mounted:

    mkdir  /home/azureuser/myfolder​


  5. Login to your Azure subscription from the VM:

    az login​


  6. Check that connection to the storage account through port 445 is possible:

    httpEndpoint=$(az storage account show 
        --resource-group $resourceGroupName 
        --name $storageAccountName 
        --query "primaryEndpoints.file" | tr -d '"')
    smbPath=$(echo $httpEndpoint | cut -c7-$(expr length $httpEndpoint))
    fileHost=$(echo $smbPath | tr -d "/")
     
    nc -zvw3 $fileHost 445​


  7. Storage account credentials are stored in the VM:

    sudo mkdir /etc/smbcredentials
    
    storageAccountKey=$(az storage account keys list 
        --resource-group $resourceGroupName 
        --account-name $storageAccountName 
        --query "[0].value" | tr -d '"')
    
    smbCredentialFile="/etc/smbcredentials/$storageAccountName.cred"
    
    if [ ! -f $smbCredentialFile ]; then
        echo "username=$storageAccountName" | sudo tee $smbCredentialFile > /dev/null
        echo "password=$storageAccountKey" | sudo tee -a $smbCredentialFile > /dev/null
    else 
        echo "The credential file $smbCredentialFile already exists, and was not modified."
    fi​


  8. Change permissions so only root can read and modify the password file:

    sudo chmod 600 $smbCredentialFile​


  9. Append mount point to /etc/fstab:

    httpEndpoint=$(az storage account show 
        --resource-group $resourceGroupName 
        --name $storageAccountName 
        --query "primaryEndpoints.file" | tr -d '"')
    smbPath=$(echo $httpEndpoint | cut -c7-$(expr length $httpEndpoint))$fileShareName
     
    if [ -z "$(grep $smbPath $mntPath /etc/fstab)" ]; then
        echo "$smbPath $mntPath cifs $nofail,vers=3.0,credentials=$smbCredentialFile,serverino,dir_mode=0777,file_mode=0$777" | sudo tee -a /etc/fstab > /dev/null
    else
        echo "/etc/fstab was not modified to avoid conflicting entries as this Azure file share was already present. You may want to double check /etc/fstab to ensure the configuration is as desired."
    fi​


  10. Mount the storage account:

    sudo mount -a​



 


3. Create a bash script that uses pg_dump to create a backup from your database. You can write something like this:


 


 

#!bin/bash
cd /home/azureuser/<folder to mount storage account>/
export PGPASSWORD="password"
date=$(date +%s)
echo $date
pg_dump -Fc -v --host=dbservername.postgres.database.azure.com --dbname=dbname --username=user@dbservername -f dbtest$date.dump
az vm deallocate -g MyResourceGroup -n MyVm #This deallocates the VM after the backup has been saved to the storage account

 


 


 


4. Schedule a task to run this script using crontab and to deallocate the VM when completed.


 

crontab -e

 


 


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For example, use the following line if you would like to have the backup run every Friday at midnight (VM time zone is UTC):
0 0 * * 5 /home/azureuser/backup_script.sh


 


5. Schedule the VM to start before the selected backup time using Logic Apps.  


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