All posts by admin

How to Fully Uninstall Cocoapods from macOS

Problem:

You run pod update but you get command not found error.

You want to fully uninstall the Cocoapods from macOS, and then to reinstall it to remove the error.

Solution:

Execute below commands:

for i in $( gem list --local --no-version | grep cocoapods );
do 
    sudo gem uninstall $i; 
done
rm -rf ~/.cocoapods

If you have a Cocoapods icon on the Launchpad then

    • Click on the  Cocoapods icon on the Launchpad,
    • Right click the Cocoapods icon in the Dock,
    • Point your mouse to Options, then click Show in Finder,
    • Right click the Cocoapods icon and select Move to Trash.

Execute below command to reinstall Cocoapods

sudo gem install cocoapods

 

How to fix “An internal error has occurred” issue of Remote Desktop Connection

Problem:

You get “An internal error has occurred” error message when trying to connect to a remote machine using Remote Desktop Connection.

Solution:

1. Type Local Security Policy to the Windows Search box.

2. Click Open link.

3. Expand Local Policies > Security Options on the left panel.

4.  Double click on System cryptography: Use FIPS compliant algorithms for encryption, hashing, and signing row on the right panel.

5. Select Enabled, click Apply and click OK.

How to increase your Wi-Fi connection speed

Problem:

You have a slow Wi-Fi connection speed.

You want to increase your Wi-Fi connection speed.

Solution:

Execute below command on Windows:

netsh wlan show interface
  • If your Signal is less than 20% then try to increase your Wi-Fi signal strength by moving your device closer to your Wi-Fi router.
  • If you cannot change your device and Wi-Fi router location then try connecting your Wi-Fi router to another Wi-Fi router (Wi-Fi extender) that acts as a new access point using LAN cable.
  • If you cannot use a LAN cable then try connecting your router to a Wi-Fi repeater that is closer to your device.
  • If your Radio type is 802.11n then try to upgrade both your device and router to support 802.11ac.
  • Try to upgrade your Wi-Fi router to support 5 GHz band.
  • Try to upgrade your Wi-Fi router to support MU-MIMO (which stands for Multi-User, Muliple Input, Multiple Output).
  • Compare Receive rate (Mbps) and Transmit rate (Mbps) before and after making a change.
  • Use Speedtest to compare your Wi-Fi connection speed before and after making a change.

How to add multiple IPs to an Amazon EC2 virtual machine

Motivation:

You have a Server 2008 R2 machine on Amazon EC2.

You want to secure multiple domains using different  SSL/TLS certificates.

Server 2008 R2 does not support Server Name Indication (SNI). Therefore you need to add multiple IPs to Server 2008 R2 machine to use different SSL/TLS certificates.

Solution:
  1. Create an EC2 virtual machine.
  2. Click on Network Interfaces tab.
  3. Click Create Network Interface button or select an existing network interface and select Actions > Attach.
  4. Select an existing network interface and select and click Manage IP Addresses to create private IPs for the network interface.
  5. Click Elastic IPs tab and allocate elastic IPs for your need.
  6. Select an elastic IP and click on Actions > Associate Address to associate a private IP of the network interface with an elastic IP.
  7. Login Windows.
  8. View the network configuration using below command, note the Default Gateway and DNS Servers information.
ipconfig /all

9. Open Control Panel\All Control Panel Items\Network and Sharing Center.

10. Click Change adapter settings link, click a Local Area Network Connection Network.

11. Manually enter one IP address, Default Gateway and DNS Servers information.

12. Click Advance… button to open Advanced TCP/IP Settings screen, and add the private IPs in the 4th step to the machine.

13. Restart the machine.

If you get any issue then try limit the number of private IPs of a network interface to 4 (including the default private IP).

How to move a WordPress instance from one server to another Linux server

Motivation:

You want to move a WordPress instance from one server to another to consolidate your websites to reduce cost.

Solution:

Install and use below Duplicator plugin to achieve your goal.

https://wordpress.org/plugins/duplicator/

User guide: https://snapcreek.com/duplicator/docs/quick-start/

If everything goes well for you then congratulation!

Otherwise, please review below possible problems and corresponding solutions.


Problem 1:

You don’t have a website on the new server.

Solution 1:

1. Create a new virtual host in the /etc/httpd/conf/httpd.conf

<VirtualHost *:80>
ServerName example.com
ServerAlias www.example.com
DocumentRoot "/var/www/www.example.com"
</VirtualHost>

2. Set 775 permission for /var/www/www.example.com

3. Restart httpd service

sudo systemctl restart httpd

Problem 2:

You are using Amazon Linux 2 server.

You are logged in as ec2-user.

You use WinSCP to upload files and edit configuration files.

You cannot modify /etc/httpd/conf/httpd.conf and /etc/php.ini.

Solution 2:

1 View permission settings for the file

ls -ld /etc/httpd/conf/httpd.conf

The result indicates that the file owner is root user and root group, not ec2-user.

2. View groups of a user

groups ec2-user

The result indicates that the ec2-user does not belong to root group.

3. Add a user to root group

sudo usermod -a -G root ec2-user

4. Grant Read-Write permission against a file to root group

sudo chmod g+rwx /etc/httpd/conf/httpd.conf
sudo chmod g+rwx /etc/php.ini

5. Logout and login to the server again.


Problem 3:

You are using Amazon Linux 2 server. The ZipArchive feature is missing.

Solution 3:

1. Execute below commands:

sudo amazon-linux-extras install php7.2
sudo yum install php-pear php-devel gcc libzip-devel zlib-devel
sudo pecl install zip-1.13.5 # we must specify a slightly older version due due to compatibility

2. Add “extension=zip.so” to /etc/php.ini

3. Restart the server

sudo reboot

Problem 4:

You don’t have a WordPress database on the new Linux server.

Solution 4:

Execute below MySQL commands:

CREATE USER 'username'@'localhost' IDENTIFIED BY 'password';
CREATE DATABASE `wp_database`;
GRANT ALL PRIVILEGES ON `wp_database`.* TO "username"@"localhost";
FLUSH PRIVILEGES;

Problem 5:

An database error occurs while restoring a website.

Solution 5:

1. Execute below commands to remove the website:

sudo chown -R ec2-user:apache /var/www/example.com
sudo chmod 2775 /var/www/example.com && find /var/www/example.com -type d -exec sudo chmod 2775 {} \;
find /var/www/example.com -type f -exec sudo chmod 0664 {} \;
rm -r /var/www/example.com

2. Upload the Duplicator files again, and restore the website again.


Problem 6:

No write access against /var/www/example.com is available for Duplicator.

Solution 6:

1. Execute below commands:

sudo chown -R ec2-user:apache /var/www/example.com
sudo chmod 2775 /var/www/example.com && find /var/www/example.com -type d -exec sudo chmod 2775 {} \;
find /var/www/example.com -type f -exec sudo chmod 0664 {} \;

2. Run http://example.com/installer.php again.

How to connect and upload files to a remote machine using OpenVPN and SSH on macOS

Motivation:

You have a server inside a network. You are granted OpenVPN and SSH access to the server. You have a MacBook. You want to upload files to the server. You want to execute a process on the server (e.g. training a machine learning model).

Procedure:

  • Request a certificate and an Open VPN configuration file (an .ovpn file) from your network administrator.
  • Install Tunnelblick https://tunnelblick.net
  • Drag the Open VPN configuration file to the Tunnelblick Configurations tab.
  • Click the Connect button.
  • On macOS, open Terminal and execute below command
ssh root@172.29.64.144 -p 7081

where 172.29.64.144 is the machine IP and 7081 is the SSH port

How to completely uninstall Python on Mac OS?

Problem:

You have an issue with a Python version (e.g. the 3.7 version) and want to install another version (e.g. the 3.6 version). In order to install a fresh version you need to uninstall the current version first.

Solution:

Assume that the current version is 3.7. Replace 3.7 with another version that you installed.

Follow these 3 steps below.

1. Remove the third-party Python 3.7 framework

sudo rm -rf /Library/Frameworks/Python.framework/Versions/3.7

2. Remove the Python 3.7 applications directory

sudo rm -rf "/Applications/Python 3.7"

3. Remove the symbolic links, in /usr/local/bin, that point to this Python version. Ensure that the links exit using below command.

ls -l /usr/local/bin | grep '../Library/Frameworks/Python.framework/Versions/3.7'

and then run the following command to remove all the links:

cd /usr/local/bin/
ls -l /usr/local/bin | grep '../Library/Frameworks/Python.framework/Versions/3.7' | awk '{print $9}' | tr -d @ | xargs rm

Source: http://stackoverflow.com

Installing a new version:

  1. Download a version from https://www.python.org/downloads/mac-osx/, double click the file and follow the instructions.
  2. Verify installation: python3 –version
  3. Install Homebrew from https://brew.sh
  4. Install virtualenv
  5. pip3 install virtualenv
    pip3 install virtualenvwrapper

5.  Create and activate a virtual environment

cd /Users/admin/Downloads/training_model/model 
python3 -m virtualenv /Users/admin/Downloads/training_model/model
source bin/activate

How to Fix the Dell Laptop “Hard Drive Not Installed” issue

Problem:

Suddenly, when turning your Dell laptop on you get the error message “Hard drive Not installed” and cannot boot into Windows.

Solution:
  1. Power your laptop and quickly press F2 key to enter BIOS.
  2. Expand System Configuration node.
  3. Click SATA Operation.
  4. Select AHCI option.
  5. Click Apply button.
  6. Click Exit button.
  7. If the problem still persists then restore BIOS settings to Default BIOS settings and try the procedure again.

 

Setting File Permissions for WordPress on IIS

Motivation:

  • You have a WordPress instance in Windows with IIS.
  • You upload a file. Its thumbnail is not shown in Media Library.
  • You change the file permission. Its thumbnail now is shown correctly in Media Library.
  • You upload another file and have to change the file permission manually again.
  • How can we make WordPress automatically set the correct permission for new uploaded files?

Procedure:

  1. Ensure that the the Identity of Application pool that the website is running under is ApplicationPoolIdentity.
  2. Execute below commands as Administrator
icacls "C:\inetpub\wwwroot\domain.com" /grant "IUSR":(OI)(CI)F /T
icacls "C:\inetpub\wwwroot\domain.com" /grant "IIS_IUSRS":(OI)(CI)F /T

3. Open IIS Manager, click on your website, click Authentication, click Anonymous Authentication (which should be the only one enabled), click Edit, select Application pool identity if it is not selected, click OK.

How to change a WordPress website’s domain name?
  • Open the wp-config.php file.
  • Add two lines to the file, right before /* That’s all, stop editing! Happy blogging. */:
define('WP_HOME','http://example.com');
define('WP_SITEURL','http://example.com');
  • Bulk edit the posts content if needed.

How to Count The Number of Source Lines of Code using Windows Command

Motivation:

  • You have a source code folder and want to know the number of source lines of code.

Procedure:

  1. Right click Start icon, click on Command Prompt (Admin) or Windows Powershell (Admin)
  2. Assume that the source code folder location is C:\Users\admin\Downloads\test, type below commands and press Enter
cd C:\Users\admin\Downloads\test

3. Assume that the source code file extension is .py, type below commands and press Enter

type *.py | Measure-Object -line

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