How to DNS cache on Windows or macOS?

Almost all operating systems cache DNS records to improve the performance of applications and speed up internet access. Browsers do cache DNS records too and to flush these the easiest way is just to close the browser and start ti again. But sometimes there is a need to flush operating system DNS cache. Here’s how you can do that easily.

How to flush DNS cache on Windows XP / Windows Vista?

  • Step 1: Open the Command Prompt
    • Click on the Start Menu and click Run. Type in cmd and hit Enter.
  • Step 2: Flush DNS
    • Type ipconfig /flushdns and hit Enter.


How to flush DNS cache on Windows Vista or Windows 7?

  • Step 1: Open the Command Prompt
    • Click on the Start Menu and type cmd in the search bar and hit Enter.
  • Step 2: Flush DNS
    • Type ipconfig /flushdns and hit Enter.

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After upgrading mac from Sierra to High Sierra git no longer works

Recently I have upgraded your macOS on my MacBook Air from Sierra to High Sierra. After the update (that took some time to complete) everything seemed to be working fine… until I was about to do some more coding and have I tried to execute git. I’ve got this error:

xcrun: error: invalid active developer path (/Library/Developer/CommandLineTools), missing xcrun at: /Library/Developer/CommandLineTools/usr/bin/xcrun

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Easiest way to start CPU mining on DigitalOcean, AWS, Google Cloud in under one minute

So, you have probably read a dozen articles or seen a handful of clips on Youtube about  how to use DigitalOcean / Amazon AWS / Google Cloud / Azure / PaperSpace or some other cloud server to mine bitcoins (or some other cryptocurrency coins) and you probably already know it’s not profitable. I know that too but still I wanted to experiment with that a bit 🙂

Many cloud providers do not allow mining on their computers since these are mostly distributed systems so they aren’t happy when some user is using a resource at full power all the time. So, once they find out that someone is mining on their hardware they usually shut these servers down or even close accounts (rarely, but it can happen!) Finding that someone is using their hardware for mining is also quite easy since the CPU will be running at 100% all the time. So it will stand out from normal usage that’s probably nowhere close to that.

Also, mining Bitcoins with CPU today is not even theoretically possible now so don’t waste your time with that. On the other side there are some alternative crypto currencies that are made to be mined only with CPU and most of these use cryptonote algorithm. If you’re going to be mining with the CPU – then simply mine these. Currently, Bytecoin, Monero and Dashcoin are the most popular. For the purpose of this post I’ll use Bytecoin (BCN).

This experiment has two goals: first one is to install everything and start mining with just one command and second is to try and limit the CPU usage so and try and stay under the radar…

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How to disable excessive resource usage alert emails?

If you have CSF firewall installed in cPanel you might noticed that you’re getting an email every time some process (usually a php script) uses more than 250MB of memory (default value) or more than 1800 secoonds (also default value).

These emails are being sent by LFD service that sends excessive resource usage alerts to the email address which is assigned to it, normally to root user account. This notification points out a particular process or service using excessive server resources and helps in identifying the resource eating process/service. We can either kill/stop the process/service to free the resource or allocate more resource to it, if necessary, increase the limits or simply do nothing and wait for it to finish it’s work.

Sample LFD email message when memory is exceeded:

—Time: Mon Nov 14 09:41:10 2016 +0530
—Account: xxxxxx
—Resource: Virtual Memory Size
—Exceeded: 205 > 200 (MB)
—Executable: /usr/bin/php
—Command Line: /usr/bin/php /home/xxxxxx/public_html/index.php
—PID: 26953 (Parent PID:24974)
—Killed: No

Sample LDF email message when execution time is exceeded:

—Time: Mon Nov 14 09:41:10 2016 +0530
—Account: xxxxxx
—Resource: Virtual Memory Size
—Exceeded: 125389 > 1800 (seconds)
—Executable: /usr/bin/php
—Command Line: /usr/bin/php /home/xxxxxx/public_html/index.php
—PID: 28429 (Parent PID:26561)
—Killed: No

Getting Started
1) Login to your WHM
2) Go to Home >> select Plugins
3) Click “ConfigServer Security & Firewall”
4) Locate and click at “Firewall Configuration” button

Method 1
This method will permanently disable the LFD excessive resource usage alert and you won’t receive any more emails. Performing this method could pose a a potential security/stability issue (you have been warned! 🙂 ).

5) Modify the value of directives PT_USERMEM and PT_USERTIME to 0.


Method 2
We will increase the values of both memory and time to stop or minimize the LFD alerts. If any process/service uses more resources than defined, you will still continue to receive the LFD alerts, but hopefully less.

5) Modify the value of directives PT_USERMEM and PT_USERTIME to desired.

PT_USERTIME = 150000

Save the changes you have made and restart CSF+LFD. By doing any of these two methods above should result in getting less or no email alerts from LFD.

How to instal s3fs-fuse on CentOS 6.8?

In case you have CentOS 6.8 server (or DigitalOcean droplet/vps) and you want to install s3fs-fuse the proposed way you’ll run into a problem: the s3fs-fuse requires fuse library version 2.8.4 or higher, but your yum install fuse fuse-devel will install you fuse 2.8.3. If you are running CentOS 7 you won’t have this problem at all, since by default, yum will install fuse 2.9.2.

To fix this problem you need to remove the fuse and install it manually.

1. Remove fuse installed by yum

yum remove fuse fuse* fuse-devel

2. Install some dependencies (for both fuse and s3fs-fuse)

yum install automake gcc-c++ git libcurl-devel libxml2-devel make openssl-devel

3. Download and install latest fuse library (version 2.9.7)

cd /usr/local/src
tar -xzvf fuse-2.9.7.tar.gz
rm -f fuse-2.9.7.tar.gz
mv fuse-2.9.7 fuse
cd fuse/
./configure --prefix=/usr
make install
export PKG_CONFIG_PATH=/usr/lib/pkgconfig:/usr/lib64/pkgconfig/

4. Test that fuse is installed (should return “2.9.7″)

pkg-config --modversion fuse

5. Install the s3fs-fuse (using the default instructions from github)

cd /usr/local/src
git clone
cd s3fs-fuse
sudo make install

6. If there were no errors along the way, this should return the s3fs-fuse version (currently 1.80)

s3fs --version

Hopefully, this will help you successfully install s3fs-fuse on your system. For details on how to use it please refer to documentation at the github page. Please do not hesitate to leave your comments below! Thank you.