AWS Operating System Unix

Incredible tutorial to more ‘RAM’ to your AWS EC2 instance

Source :



Check the System for Swap Information

Before we begin, we should take a look at our server’s storage to see if we already have some swap space available. While we can have multiple swap files or swap partitions, one should generally be enough.

We can see if the system has any configured swap by using swapon, a general-purpose swap utility. With the -s flag, swapon will display a summary of swap usage and availability on our storage device:

swapon -s

If nothing is returned by the command, then the summary was empty and no swap file exists.

Another way of checking for swap space is with the free utility, which shows us the system’s overall memory usage. We can see our current memory and swap usage (in megabytes) by typing:

free -m
             total       used       free     shared    buffers     cached
Mem:          3953        315       3637          8         11        107
-/+ buffers/cache:        196       3756
Swap:            0          0       4095

As you can see, our total swap space in the system is 0. This matches what we saw with swapon.

Check Available Storage Space

The typical way of allocating space for swap is to use a separate partition that is dedicated to the task. However, altering the partition scheme is not always possible due to hardware or software constraints. Fortunately, we can just as easily create a swap file that resides on an existing partition.

Before we do this, we should be aware of our current drive usage. We can get this information by typing:

df -h
Filesystem      Size  Used Avail Use% Mounted on
/dev/vda1        59G  1.5G   55G   3% /
devtmpfs        2.0G     0  2.0G   0% /dev
tmpfs           2.0G     0  2.0G   0% /dev/shm
tmpfs           2.0G  8.3M  2.0G   1% /run
tmpfs           2.0G     0  2.0G   0% /sys/fs/cgroup

Note: the -h flag simply tells dh to output drive information in a human-friendly reading format. For example, instead of outputting the raw number of memory blocks in a partition, df -h will tell us the space usage and availability in M (for megabytes) or G (for gigabytes).

As you can see on the first line, our storage partition has 59 gigabytes available, so we have quite a bit of space to work with. Keep in mind that this is on a fresh, medium-sized VPS instance, so your actual usage might be very different.

Although there are many opinions about the appropriate size of a swap space, it really depends on your application requirements and your personal preferences. Generally, an amount equal to or double the amount of memory on your system is a good starting point.

Since my system has 4 gigabytes of memory, and doubling that would take a larger chunk from my storage space than I am willing to part with, I will create a swap space of 4 gigabytes to match my system’s memory.

Create a Swap File

Now that we know our available storage space, we can go about creating a swap file within our filesystem. We will create a file called swapfile in our root (/) directory, though you can name the file something else if you prefer. The file must allocate the amount of space that we want for our swap file.

The fastest and easiest way to create a swap file is by using fallocate. This command creates a file of a preallocated size instantly. We can create a 4 gigabyte file by typing:

sudo fallocate -l 4G /swapfile

After entering your password to authorize sudo privileges, the swap file will be created almost instantly, and the prompt will be returned to you. We can verify that the correct amount of space was reserved for swap by using ls:

ls -lh /swapfile
-rw-r--r-- 1 root root 4.0G Oct 30 11:00 /swapfile

As you can see, our swap file was created with the correct amount of space set aside.

Enable a Swap File

Right now, our file is created, but our system does not know that this is supposed to be used for swap. We need to tell our system to format this file as swap and then enable it.

Before we do that, we should adjust the permissions on our swap file so that it isn’t readable by anyone besides the root account. Allowing other users to read or write to this file would be a huge security risk. We can lock down the permissions with chmod:

sudo chmod 600 /swapfile

This will restrict both read and write permissions to the root account only. We can verify that the swap file has the correct permissions by using ls -lh again:

ls -lh /swapfile
-rw------- 1 root root 4.0G Oct 30 11:00 /swapfile

Now that our swap file is more secure, we can tell our system to set up the swap space for use by typing:

sudo mkswap /swapfile
Setting up swapspace version 1, size = 4194300 KiB
no label, UUID=b99230bb-21af-47bc-8c37-de41129c39bf

Our swap file is now ready to be used as a swap space. We can begin using it by typing:

sudo swapon /swapfile

To verify that the procedure was successful, we can check whether our system reports swap space now:

swapon -s
Filename                Type        Size    Used    Priority
/swapfile               file        4194300 0     -1

This output confirms that we have a new swap file. We can use the free utility again to corroborate our findings:

free -m
             total       used       free     shared    buffers     cached
Mem:          3953        315       3637          8         11        107
-/+ buffers/cache:        196       3756
Swap:         4095          0       4095

Our swap has been set up successfully, and our operating system will begin to use it as needed.

Make the Swap File Permanent

Our swap file is enabled at the moment, but when we reboot, the server will not automatically enable the file for use. We can change that by modifying the fstab file, which is a table that manages filesystems and partitions.

Edit the file with sudo privileges in your text editor:

sudo nano /etc/fstab

At the bottom of the file, you need to add a line that will tell the operating system to automatically use the swap file that you created:

/swapfile   swap    swap    sw  0   0

When you are finished adding the line, you can save and close the file. The server will check this file on each bootup, so the swap file will be ready for use from now on.

AWS General Operating System

Redirect to https and www

The following .htaccess technique redirects qualified requests to the https and www versions of your web pages. Add to your site’s root .htaccess file:

# Canonical https/www

RewriteCond %{HTTP_HOST} !^www\.
RewriteRule ^(.*)$ http://www.%{HTTP_HOST}/$1 [R=301,L]

RewriteCond %{HTTPS} off
RewriteRule ^(.*)$ https://%{HTTP_HOST}%{REQUEST_URI} [L,R=301]

This code does the following:

Checks if mod_rewrite is available
Check if the request does not include www
Checks if HTTPS is off,

No editing is required with this code; it’s entirely plug-n-play.


Easy to update Drupal 7 latest security modules

drupal Notice: Undefined variable: not_empty_panel in include() (line 15 of /sites/all/themes/garbage/nucleus/nucleus/tpl/panel.tpl.php).


Go to settings.php

go to

455 vim sites/default/settings.php
457 yum search gd
458 yum install php73-gd.x86_64

459 service httpd restart
460 vim sites/default/settings.php

$update_free_access = FALSE;
$update_free_access = TRUE;

Execute again

Book Study Recommendation Books Symfony

BOOK : mastering symfony – Take away

General SQL

mysql 8

Create new User

– Full privileges




Force to write debugging messages in PhpUnit

If you found yourself trying to debug PhpUnit the following php line will relieve your frustration. This line will instantly output the message or variables values that you are trying to debug

fwrite(STDERR, "TEST");

AWS – SQS – LAMBDA – CloudWatch – Slack – DLQ – SNS

I am currently working on a transactional platform where orders are pushed to a Queue SQS then pulled and processed by lambda.

In a problematic situation , lambda triggers AWS SNS which will notify sysOp via email and a Slack Channel. Awesome ! And more importantly a DLQ – Dead-Letter Queue will contain workers waiting to be reprocessed and sent to our Technical Customer Service Department to analyze what went wrong


New Relic – Monitoring System

Adding more visibility to my teams

New Relic is a web application performance service designed to work in a real time with your live web app. New Relic Infrastructure provides flexible, dynamic server monitoring. … It can be considered as the plumbing that makes web apps run faster.


PHP 7.4 – Null Coalescing Assignment Operator

Null Coalescing Assignment Operator

In the long run, this code could be a bit difficult to maintain. So, aiming to help developers to write more intuitive code, this RFC proposes the introduction of the null coalescing assignment operator (??=). So, instead of writing the previous code, we could write the following:

$this->request->data['comments']['user_id'] ??= ‘value’;

New Features php-7.4

source :

2. New Features

- Core:
  . Added support for typed properties. For example:

        class User {
            public int $id;
            public string $name;

    This will enforce that $user->id can only be assigned integers and
    $user->name can only be assigned strings. For more information see the

  . Added support for coalesce assign (??=) operator. For example:

        $array['key'] ??= computeDefault();
        // is roughly equivalent to
        if (!isset($array['key'])) {
            $array['key'] = computeDefault();


  . Added support for unpacking inside arrays. For example:

        $arr1 = [3, 4];
        $arr2 = [1, 2, ...$arr1, 5];
        // $arr2 == [1, 2, 3, 4, 5]