Notes

/** @var \Drupal\Core\Database\Query\SelectExtender $query */
echo $query->__toString();
var_dump($query->getArguments());

 /* Extra small devices (phones, 600px and down) */
  @media only screen and (max-width: 600px) {
  }

  /* Small devices (portrait tablets and large phones, 600px and up) */
  @media only screen and (min-width: 600px) {
  }

  /* Medium devices (landscape tablets, 768px and up) */
  @media only screen and (min-width: 768px) {
  }

  /* Large devices (laptops/desktops, 992px and up) */
  @media only screen and (min-width: 992px) {
  }

  /* Extra large devices (large laptops and desktops, 1200px and up) */
  @media only screen and (min-width: 1200px) {
  }

{#  it will work either external or internal link #}
{{ node.field_image_link.get(0).getUrl().toString() }}

drush sql-query "DELETE FROM key_value WHERE collection='system.schema' AND name='module_name';"

_{source: https://www.drupal.org/node/2487215}

/** @var array $countries */
$countries = \Drupal::service('country_manager')
  ->getList();
// Transform TranslatableMarkup object into a string.
array_walk($countries, function (&$translation) {
  /** @var  Drupal\Core\StringTranslation\TranslatableMarkup $translation */
  $translation = $translation->render();
});
var_dump($countries);

Drupal 8 ships with a service to easily retrieve all countries by code. Be sure to use dependency injection.

drush ev "\Drupal::configFactory()->getEditable('configuration.name')->delete();"

drush sqlq "DELETE FROM cache_config"
drush sqlq "DELETE FROM config WHERE name = 'field.storage.<module_name>.<field_machine_name>' OR data LIKE '%field.storage.<module_name>.<field_machine_name>%'"
drush sqlq "DELETE FROM config_snapshot  WHERE name = 'field.storage.<module_name>.<field_machine_name>' OR data LIKE '%field.storage.<module_name>.<field_machine_name>%'"

On my case It was happening with "taxonomy_term" module and field named "field_location".

/* @var \Drupal\file\FileInterface[] $files */
$files = \Drupal::entityTypeManager()
  ->getStorage('file')
  ->loadByProperties(['uri' => $uri]);

Script:

#!/bin/bash

# Help menu
print_help() {
cat <<-HELP
This script is used to fix permissions of a Drupal installation
you need to provide the following arguments:

  1) Path to your Drupal installation.
  2) Username of the user that you want to give files/directories ownership.
  3) HTTPD group name (defaults to www-data for Apache).

Usage: (sudo) bash ${0##*/} --drupal_path=PATH --drupal_user=USER --httpd_group=GROUP
Example: (sudo) bash ${0##*/} --drupal_path=/usr/local/apache2/htdocs --drupal_user=john --httpd_group=www-data
HELP
exit 0
}

if [ $(id -u) != 0 ]; then
  printf "**************************************\n"
  printf "* Error: You must run this with sudo or root*\n"
  printf "**************************************\n"
  print_help
  exit 1
fi

drupal_path=${1%/}
drupal_user=${2}
httpd_group="${3:-www-data}"

# Parse Command Line Arguments
while [ "$#" -gt 0 ]; do
  case "$1" in
    --drupal_path=*)
        drupal_path="${1#*=}"
        ;;
    --drupal_user=*)
        drupal_user="${1#*=}"
        ;;
    --httpd_group=*)
        httpd_group="${1#*=}"
        ;;
    --help) print_help;;
    *)
      printf "***********************************************************\n"
      printf "* Error: Invalid argument, run --help for valid arguments. *\n"
      printf "***********************************************************\n"
      exit 1
  esac
  shift
done

if [ -z "${drupal_path}" ] || [ ! -d "${drupal_path}/sites" ] || [ ! -f "${drupal_path}/core/modules/system/system.module" ] && [ ! -f "${drupal_path}/modules/system/system.module" ]; then
  printf "*********************************************\n"
  printf "* Error: Please provide a valid Drupal path. *\n"
  printf "*********************************************\n"
  print_help
  exit 1
fi

if [ -z "${drupal_user}" ] || [[ $(id -un "${drupal_user}" 2> /dev/null) != "${drupal_user}" ]]; then
  printf "*************************************\n"
  printf "* Error: Please provide a valid user. *\n"
  printf "*************************************\n"
  print_help
  exit 1
fi

cd $drupal_path
printf "Changing ownership of all contents of "${drupal_path}":\n user => "${drupal_user}" \t group => "${httpd_group}"\n"
chown -R ${drupal_user}:${httpd_group} .

printf "Changing permissions of all directories inside "${drupal_path}" to "rwxr-x---"...\n"
find . -type d -exec chmod u=rwx,g=rx,o= '{}' \;

printf "Changing permissions of all files inside "${drupal_path}" to "rw-r-----"...\n"
find . -type f -exec chmod u=rw,g=r,o= '{}' \;

printf "Changing permissions of "files" directories in "${drupal_path}/sites" to "rwxrwx---"...\n"
cd sites
find . -type d -name files -exec chmod ug=rwx,o= '{}' \;

printf "Changing permissions of all files inside all "files" directories in "${drupal_path}/sites" to "rw-rw----"...\n"
printf "Changing permissions of all directories inside all "files" directories in "${drupal_path}/sites" to "rwxrwx---"...\n"
for x in ./*/files; do
  find ${x} -type d -exec chmod ug=rwx,o= '{}' \;
  find ${x} -type f -exec chmod ug=rw,o= '{}' \;
done
echo "Done setting proper permissions on files and directories"

Usage: 

sudo fix-permissions.sh \
--drupal_path=/path/to/the/drupal/install \
--drupal_user=your_desired_user

# composer.json file:
# {
#   "name": "drupal/drupal",
#    ..... 
#   "require": {
#           "drupal/core": "^8.6.0",
#    .....
#  }
# Update Drupal core
composer update drupal/core webflo/drupal-core-require-dev --with-dependencies