Boot partitions from installations prior to the 16.04 era are terribly small. When you install updates and encounter errors due to a full /boot partition, consider risizing it.

If you can't do the steps described below, ask someone experienced to help you out.
This has worked 100% so far. 1 out of 1 tries. ;)

Scenario A: There is unassigned space on your physical drive

When there is some unpartitioned space on your drive, increasing the size of /boot is actually very easy (even though the list below is rather long). It only takes a...

New features:

geordi delete_dumps [directory]

Recursively search for files ending in *.dump and offer to delete those. When no argument is given, two default directories are searched for dump files: the current working directory and ~/dumps (for dumps created with geordi).

geordi drop_databases

Delete local MySQL/MariaDB and Postgres databases that are not whitelisted.

Authentication is handled via PAM for Postgres and MariaDB, via .my.cnf with fallback to mysql -p for MySQL. Different connection methods can be chosen via ...

Rails offers a way to prepend (or append) view paths for the current request. This way, you can make the application use different view templates for just that request.

Example

A use case of this is a different set of view templates that should be used under certain circumstances:

class UsersController < ApplicationController

  before_action :prepare_views
  
  def index
    # ...
  end    
  
  private
  
  def prepare_views
    if <condition>
      prepend_view_path Rails.root.join('app', 'views', 'special')
    end
  end
 ...

When you have string contents (e.g. a generated binary stream, or data from a remote source) that you want to store as a file using Carrierwave, here is a simple solution.

While you could write your string to a file and pass that file to Carrierwave, why even bother? You already have your string (or stream).
However, a plain StringIO object will not work for Carrierwave's ActiveRecord integration:

>> Attachment.create!(file: StringIO.new(contents))
TypeError: no implicit conversion of nil into String

This is because Carrierwav...

Form fields can be rendered as noneditable by setting the disabled or the readonly attribute. Be aware of the differences:

disabled fields

• don’t post to the server
• don’t get focus
• are skipped while tab navigation
• available for button, fieldset, input, select, textarea, command, keygen, optgroup, option

Browser specific behavior:

• IE 11: text inputs that are descendants of a disabled fieldset appear disabled but the user can still interact with them
• Firefox: selecting text in a disabled text field is no...

Trying to open a vnc window with geordi geordi vnc ended up with this error:

> VNC viewer could not be opened:
vncviewer: ConnectToTcpAddr: connect: Connection refused

Check if vncserver 17 (default geordi session) is running:

ps -aux|grep vnc

If you see Xvnc4 :17 then the server is already running. Kill this server if it is already running.

vncserver -kill :17

Als...

mysql> SELECT @@global.version;
+------------------+
| @@global.version |
+------------------+
| 5.6.30           |
+------------------+
1 row in set (0,00 sec)

MySQL 5.6 Reference Manual says "BLOB and TEXT columns cannot have DEFAULT values".

If you want to run migrations in development here are two variants which might help. If you are not sure about the side effects (e.g. your application is broken when it doesn't set additional default values on application side, too...

If you want to make a screenshot of a website that works well in print or on a high-DPI screen (like Apple Retina displays), here is how you can capture a high-resolution screenshot.

You can do this without an addon:

• Open the website
• If you have multiple monitoros:
  • Resize the Chrome window so it covers multiple monitors (in Linux you can hold ALT and resize by dragging with the right mouse button)
  • Zoom into the page using CTRL + and CTRL - so it covers most of the window area. Leave a little padding on the left and right so...

About-Payments is here to help you to accept payments online and
find the best payment service provider for your e-commerce business.

TL;DR Use user.update!(remove_avatar: true) to delete attachments outside of forms. This will have the same behavior as if you were in a form.

As you know, Carrierwave file attachments work by mounting an Uploader class to an attribute of the model. Though the database field holds the file name as string, calling the attribute will always return the uploader, no matter if a file is attached or not. (Side note: use #present? on the uploader to check if the file exists.)

class User < ApplicationRecord
  mount :avatar, ...

This is painful. Consider using Microsoft Office or switching careers. If you need to write < 20 letters consider doing it manually.

So you didn't listen and here it comes:

1. Ignore the Mail Merge Wizard. It will crash or destroy your document.
2. Export your addresses, recipient names, etc. as a .ods spreadsheet (.xls, .xlsx, .ods). Use any columns that work for you, but be consistent. I like to use one column for the address, one column for the salutation line.
3. Import the spreadsheet as an address book source: *Tools => Add...

When making requests using curl, no cookies are sent or stored by default.
However, you can tell curl to re-use cookies received earlier (or forge your own cookies).

There are 2 command line switches you need to use:

• -c will write cookies to a given file
• -b will read cookies from a given file

Example

The remote server sets a "foo" cookie to value "bar". We tell curl to store them to a file at /tmp/cookies using the -c switch.

$ curl -c /tmp/cookies http://httpbin.org/cookies/set?foo=bar

You may look at the file, ...

You should avoid using application models in your migrations. But how else could you create records in a migration?

The most basic way is to write plain SQL, but since INSERT statements are no pleasant write for Rubyists, here is a simple wrapper:

Record creation helper for migrations

The helper method below takes a table name and a hash of attributes, which it inserts into the specified table. Copy it over to your migration and profit!

  private

  def insert_record(table, **attributes)
    attributes.merge!...

When you print (or print preview) and elements are cut off (e.g. after 1st page, or "randomly") you should check your CSS rules for these:

• Is there an element with "display: inline-block" that surrounds your content? Make sure it has "display: block" for printing.
  This primarily affects Firefox and Internet Explorer. Chrome seems to be able to handle inline-block elements in most cases.

• Does the element itself, or a container, define "overflow: hidden"? Use "overflow: auto" (or maybe "overflow: visible") instead.

• Is th...

By default, browsers will not wrap text at syllable boundaries. Text is wrapped at word boundaries only.

This card explains some options to make browsers wrap inside a long word like "Donaudampfschifffahrt".

Option 1: hyphens CSS property (preferred)

Modern browsers can hyphenate natively. Use the hyphens CSS property:

hyphens: auto

There is also hyphens: none (disable hyphenations even at ­ entities) and hyphens: manual (hy...

Summary: Don't add chromedriver-helper to the Gemfile

• the executables might break your tests in projects where chromedriver-helper is not in the Gemfile
• developers with different chrome versions will have problems using the same chromedriver-helper version

Background

If you install the chromedriver-helper gem, but don't have it in you Gemfile, your selenium tests might fail with:

Selenium::WebDriver::Error::WebDriverError: unable to connect to chromedriver 127.0.0.1:9515

The reason is that chromedriver-helper ov...

We're usually running Ubuntu LTS versions. Sometimes newer hardware requires packages from more recent Ubuntu releases that only come with 6 months of support. If there is really no other way, it's possible to install packages from later Ubuntu releases

Caution: Pay really close attention to what you're doing. Depending on the package, this process may require upgrading a lot of dependencies, possibly breaking the system! You really should not do this unless you've carefully calculated the impact on your system

Preparation

First,...

Checking if a JavaScript value is of a given type can be very confusing:

• There are two operators typeof and instanceof which work very differently.
• JavaScript has some primitive types, like string literals, that are not objects (as opposed to Ruby, where every value is an object).
• Some values are sometimes a primitive value (e.g. "foo") and sometimes an object (new String("foo")) and each form requires different checks
• There are three different types for null (null, undefined and NaN) and each has different rules for...

An end-to-end test (E2E test) is a script that remote-controls a web browser with tools like Selenium WebDriver. This card shows basic techniques for fixing a flaky E2E test suite that sometimes passes and sometimes fails.

Although many examples in this card use Ruby, Cucumber and Selenium, the techniques are applicable to all languages and testing tools.

Why tests are flaky

Your tests probably look like this:

When I click on A
And I click on B
And I click on C
Then I should see effects of C

A test like this works fine...

When your public-facing application has a longer downtime for server maintenance or long migrations, it's nice to setup a maintenance page to inform your users.

When delivering the maintenance page, be very careful to send the correct HTTP status code. Sending the wrong status code might get you kicked out of Google, or undo years of SEO work.

Popular footguns

Here are some ways to shoot yourself in the foot during maintenance:

• If all your routes send a "200 OK" with a HTML body "We're b...

Slides for Henning's talk on Sep 21st 2017.

Understanding sync vs. async control flow

Talking to synchronous (or "blocking") API

print('script start')
html = get('/foo')
print(html)
print('script end')

Script outputs 'script start', (long delay), '<html>...</html>', 'script end'.

Talking to asynchronous (or "evented") API

print('script start')
get('foo', done: function(html) {
  print(html)
})
print('script end')

Script outputs 'script start', 'script end', (long ...

If you are using PDFKit / wkhtmltopdf, you might as well want to use custom fonts in your stylesheets. Usually this should not be a problem, but at times they include misleading Meta-information that leads to a strange error in the PDF.

The setup

• The designer gave you two fonts named something like BrandonText-Regular and BrandonText-Bold. (With flawed Meta-information)
• You have a HTML string to be rendered by PDFKit
• For demonstration purposes, this strin...