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cloud engineer

template

EBS volume stuck in CloudFormation

When running CloudFormation, all the resources are being created with no problem. However it seems to be getting stuck at creating or mounting a volume. The CloudFormation fails and initiates a rollback. This is the error I am getting. 

Volume attachment between volume-id vol-xxxxxxxx and instance-id i-xxxxxxx at device /dev/xvda is attaching

This turned out to be a conflict on HVM EC2 instances because /dev/sda1 is being remapped to /dev/xvda. My second drive is also mapped to /dev/xvda. The fix was to simply to map it slightly different to avoid mapping conflict.

Here’s the original mapping.

Boot:   /dev/xvda
Device: /dev/xvda
Device: /dev/xvdb

Here’s the fix.

Boot:   /dev/xvda
Device: /dev/xvdb
Device: /dev/xvdc

WordPress Numeric Pagination

Here’s how to add numeric pagination on your WordPress pages.

Add this code to functions.php.

function pagination($pages = '', $range = 4) {
  $showitems = ($range * 2)+1;
  global $paged;
  if(empty($paged)) $paged = 1;
  if($pages == '') {
    global $wp_query;
    $pages = $wp_query->max_num_pages;
    if(!$pages) {
      $pages = 1;
    }
  }
  if(1 != $pages) {
    echo '<p><div class="pagination"><span>Page' . $paged . ' of  ' . $pages . '</span>   ';
    if($paged > 2 && $paged > $range+1 && $showitems < $pages) echo '<a href="' . get_pagenum_link(1) . '"><< First</a>';
    if($paged > 1 && $showitems < $pages) echo '<a href="'.get_pagenum_link($paged - 1).'">< Previous</a>';
    for ($i=1; $i <= $pages; $i++) {
      if (1 != $pages &&( !($i >= $paged+$range+1 || $i <= $paged-$range-1) || $pages <= $showitems )) {
        echo ($paged == $i)? '<span class="current">' . $i . '</span>' : '<a href="' . get_pagenum_link($i) . '"class="inactive">' . $i . '</a>';
      }
    }
    if ($paged < $pages && $showitems < $pages) echo '<a href="' . get_pagenum_link($paged + 1) . '">Next ></a>';
    if ($paged < $pages-1 && $paged+$range-1 < $pages && $showitems < $pages) echo '<a href="' . get_pagenum_link($pages) . '">Last >></a>';
    echo '</div></p>';
  }
}

To display, comment out ‘the_post_navigation’ function and add the ‘pagination’ function instead in your template files.

//the_posts_navigation();
pagination();

Code courtesy of webdesignsun.

EFS CloudFormation

Here’s a simple EFS CloudFormation template with a one mount target.

{
	"AWSTemplateFormatVersion": "2010-09-09",
	"Description": "EFS example setup",
	"Parameters": {
		"VPC": {
			"Description": "VPC ID",
			"Type": "AWS::EC2::VPC::Id"
		},
		"Subnet": {			
			"Description": "Subnet ID",
			"Type": "AWS::EC2::Subnet::Id"
		},
		"EC2SecurityGroup": {
			"Description": "Security Group for EC2 instance",
			"Type": "AWS::EC2::SecurityGroup::Id"
		}	
	},
	"Resources": {
		"EFSFileSystem": {
			"Type" : "AWS::EFS::FileSystem",
			"Properties" : {
				"FileSystemTags" : [
					{"Key" : "Name", "Value" : {"Ref": "AWS::StackName"}}
				]
			}
		},
		"EFSMountTarget": {
			"Type": "AWS::EFS::MountTarget",
			"Properties": {
				"FileSystemId": {"Ref": "EFSFileSystem"},
				"SubnetId": { "Ref": "Subnet" },
				"SecurityGroups": [{"Ref": "EFSSecurityGroup"}]        
			}
		},
		"EFSSecurityGroup": {
			"Type": "AWS::EC2::SecurityGroup",
			"Properties": {
				"GroupDescription": "Allowing access to EFS",
				"VpcId": {"Ref": "VPC"},
				"SecurityGroupIngress": [{
					"IpProtocol": "tcp",
					"FromPort": 2049,
					"ToPort": 2049,
					"SourceSecurityGroupId": {"Ref": "EC2SecurityGroup"}
				}]
			}
		}				
	}
}