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…

Continue Reading


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.

PT_USERMEM = 0
PT_USERTIME = 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_USERMEM = 500
PT_USERTIME = 150000

Finish
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
wget https://github.com/libfuse/libfuse/releases/download/fuse-2.9.7/fuse-2.9.7.tar.gz
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
make install
export PKG_CONFIG_PATH=/usr/lib/pkgconfig:/usr/lib64/pkgconfig/
ldconfig

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)

git clone https://github.com/s3fs-fuse/s3fs-fuse.git
cd s3fs-fuse
./autogen.sh
./configure
make
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.


Installig git on CentOS 6 fails with Requires: libcurl.so.3()(64bit)

Today I had to install git on one server running on CentOS 6, but yum install git returned the following error:

Error: Package: git-1.7.12.4-1.el5.rf.x86_64 (rpmforge)
Requires: libcurl.so.3()(64bit)

To fix this bug you have to run this command:

and then confirm the removal of that package:

Loaded plugins: fastestmirror, security
Setting up Remove Process
Resolving Dependencies
--> Running transaction check
---> Package rpmforge-release.x86_64 0:0.5.3-1.el5.rf will be erased
--> Finished Dependency Resolution

Dependencies Resolved

=============================================================================================================================================================================================================================================
 Package                                                       Arch                                                Version                                                      Repository                                              Size
=============================================================================================================================================================================================================================================
Removing:
 rpmforge-release                                              x86_64                                              0.5.3-1.el5.rf                                               @rpmforge                                               13 k

Transaction Summary
=============================================================================================================================================================================================================================================
Remove        1 Package(s)

Installed size: 13 k
Is this ok [y/N]: y
Downloading Packages:
Running rpm_check_debug
Running Transaction Test
Transaction Test Succeeded
Running Transaction
  Erasing    : rpmforge-release-0.5.3-1.el5.rf.x86_64                                                                                                                                                                                    1/1
  Verifying  : rpmforge-release-0.5.3-1.el5.rf.x86_64                                                                                                                                                                                    1/1

Removed:
  rpmforge-release.x86_64 0:0.5.3-1.el5.rf

Complete!
[root@hosted-by boot]#

After that the standard yum install git will work just fine!


Laravel 5.4 migration: Specified key was too long error solution

Three days ago Laravel 5.4 was released, so I have decided to give it a try. I have made a new Laravel 5.4 project and just when I was about to run the default auth migrations that are shipped with the Laravel almost without any other changes, I got these two red errors:

[Illuminate\Database\QueryException]
SQLSTATE[42000]: Syntax error or access violation: 1071 Specified key was too long; max key length is 767 bytes (SQL: alter table `users` add unique `users_email_unique`(`email`))

 

[PDOException]
SQLSTATE[42000]: Syntax error or access violation: 1071 Specified key was too long; max key length is 767 bytes

What the hell is going on!?!? I have checked the migrations file and everything was okay there unchanged compared to Laravel 5.3. But, according to Laravel Documentation one thing changed:

Laravel 5.4 uses the utf8mb4 character set by default, which includes support for storing “emojis” in the database. If you are upgrading your application from Laravel 5.3, you are not required to switch to this character set.

And, according to their documentation the problem is that I’m running version of MySQL prior to 5.7.7 or MariaDB prior to 10.2.2 (my case). In case you are running versions of MySQL or MariaDB greater than these than most probably that you won’t have this problem at all.

In case you are having this problem – here are the possible solutions:

1. Upgrade MariaDB / MySQL

To update MariaDB on Mac using Brew, first you need to unlink the current one using:

brew unlink mariadb

and then install a dev one using

brew install mariadb --devel

That will install MariaDB version 10.2.3 that works fine. Remember that after installation is done you need to  stop/start the service:

brew services stop mariadb
brew services start mariadb

2. Stick with utf8

In case you don’t want to use the utf8mb4 (that is now setup by default in Laravel 5.4) – instead you want to stick with utf8 that was in use in Laravel 5.3 and all versions before, simply edit /config/database.php  and find these two lines in mysql driver:

'charset' => 'utf8mb4',
'collation' => 'utf8mb4_unicode_ci',

and replace them with with

'charset' => 'utf8',
'collation' => 'utf8_unicode_ci',

That will stop using the utf8mb4 and will change back to utf8. The good thing about this is that you’ll be able to fit 25% more characters into the same columns in database compared with utf8mb4 and that you’ll be able to use existing databases and projects without the need of converting them if you don’t want to. And the downside is that some characters will not be able to be saved to database like this mac command character ⌘ or some emojis. Utf8 can only store Plane Unicode while utf8mb4 can store any unicode character.  Utf8mb4 is also 100% backwards compatible with utf8.

3. Use utf8mb4 without MySQL/MariaDB upgrade

In case you want to use utf8mb4 but you don’t want to or simply can’t upgrade your MySQL/MariaDB there is a simple solution  proposed by Laravel documentation. All you need to do is edit AppServiceProvider located at App\Providers\AppServiceProvider.php and add the following line to the boot() method and load the Schema facade:

use Illuminate\Support\Facades\Schema;

/**
 * Bootstrap any application services.
 *
 * @return void
 */
public function boot()
{
    Schema::defaultStringLength(191);
}

What that will do is actually change the default maximum field length in the database and actually shorten your maximum string length from 255 to maximum of 191 characters (utf8 uses 3 bytes per character while utf8mb4 uses 4 bytes per character your field can now hold 25% less characters 255 * 75% = 191.25). So if you don’t set the string field by hand in the migration the new default will be 191. You can increase the length if you need it manually by defining it:

$table->string('name', 255);

But this will not be possible on indexed fields since these can’t be longer than 191 characters. So keep this in mind in case you’re planing to use utf8mb4.

In case you want to convert the database from utf8 to utf8mb4 for any existing projects or if you are upgrading from Larvel 5.3 or older to Laravel 5.3 this is the code you need to run for every database, table and column:

Make sure you have the database backups before making these changes!!!!

# For each database:
ALTER DATABASE database_name CHARACTER SET = utf8mb4 COLLATE = utf8mb4_unicode_ci;

# For each table:
ALTER TABLE table_name CONVERT TO CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci;

# For each column:
ALTER TABLE table_name CHANGE column_name column_name VARCHAR(191) CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci;

# (Don’t just blindly copy-paste this! The exact statement depends on the column type, maximum length, and other properties. The above line is just an example for a `VARCHAR` column.)

Once again: when converting from utf8 to utf8mb4, the maximum length of a column or index key is unchanged in terms of bytes but since utf8mb4 uses 25% more bytes per character your columns can now accept less characters. Therefore, it is smaller in terms of characters, because the maximum length of a character is now four bytes instead of three.

For example, a TINYTEXT column can hold up to 255 bytes, which correlates to 85 three-byte or 63 four-byte characters. Let’s say you have a TINYTEXT column that uses utf8 but must be able to contain more than 63 characters. Given this requirement, you can’t convert this column to utf8mb4 unless you also change the data type to a longer type such as TEXT — because if you’d try to fill it with four-byte characters, you’d only be able to enter 63 characters, but not more.

The same goes for index keys. The InnoDB storage engine has a maximum index length of 767 bytes, so for utf8 or utf8mb4 columns, you can index a maximum of 255 or 191 characters, respectively. If you currently have utf8 columns with indexes longer than 191 characters, you will need to index a smaller number of characters when using utf8mb4.

If you plan on using utf8mb4 make sure to setup your MySQL server accordingly by editing /etc/my.cnf file accordingly:

[client]
default-character-set = utf8mb4

[mysql]
default-character-set = utf8mb4

[mysqld]
character-set-client-handshake = FALSE
character-set-server = utf8mb4
collation-server = utf8mb4_unicode_ci

Conclusion

If your application won’t use any special characters or emojis or languages such as Chinese, Japanese, and Korean you’re most probably fine sticking with utf8. But if you can – you should move to utf7mb4 since that will stop you from loosing 4-byte characters when a user ads these in comments or in message or whenever you store these in your database. You should always strive to full unicode support everywhere in your apps and updating your database and code might take some time but it’s definitely worth the time and effort.