Matthias Schoettle

PhD Student & Software Developer

Category: Howto (page 1 of 2)

iOS: How to fix/change Voicemail number

Recently, a friends voice mail “button” did not work anymore. Upon calling the voice mail, an audio error message appeared saying that the voice mail is not available or cannot be reached (something like that).

Unfortunately, Apple does not want you to just change the associated voice mail phone number that is called when tapping on “Voicemail”.

Fortunately, there is a shortcut:

  1. Go to the phone’s keypad
  2. Dial *#5005*86# and “call it”
  3. A phone number will appear, which is the one currently associated with the voice mail.  Write this down just in case.
  4. Now, call *5005*86*<insertPhoneNumber># and replace the placeholder with your phone number, starting with the country code (1 in this case for North America). For example, 14381234567.
  5. The voice mail button should now work.

This approach worked on the TELUS network (using Koodo). If it doesn’t work for you, revert the phone number to the one written down in step 3 and contact your provider.


Firefox close tab button on hover

There are probably extensions that allow to do that, however, this is not necessary as I will show in this post. Maybe you’ve seen the functionality in Safari or just wondered why the close button for tabs in Firefox can’t just always be there. In Safari, the close button appears when hovering over the tab itself.

The following modification adds this functionality to Firefox. You need to create a file called userChrome.css with the following content:

.tabbrowser-tab:not([selected]) .tab-close-button {
        visibility: hidden !important;
        margin-left: -16px !important;

.tabbrowser-tab:not([selected]):hover .tab-close-button {
        visibility: visible !important; 
        margin-left: 0px !important;

Place this file into the chrome folder inside your profile’s directory. Follow the directions from Mozilla to find out where to find the profile’s directory location.

Update: It just tried this again myself due to a fresh installation and you also need to change the browser.tabs.tabClipWidth preference from it’s default value (140) to 99.

Then just restart Firefox and you are done.

Source: Post on Neowin Forums

Move more than one directory into a new repository

I just realized that my previous post on how to move one directory from one repository to another really only works for one directory.

Fortunately, there is a very easy solution to that using a nice little tool called git_filter.

Basically follow the instructions of it’s README. Then, all I did was put the two directories into the filter file. It is important to note here that this file had to end with an empty line in my case, otherwise the last directory will be ignored.

You will get a new branch, which can be pushed to an empty repository:

git remote add origin_repoB <url of repo>
git push origin_repoB <localBranch>:master

It also works for one directory and is a lot faster compared to the other method.

Move directory from one repository to another, preserving history

I just moved one directory within a Git repository to a directory within another repository including its history. For example:



The goal is to move directoryToKeep into repositoryB with its history, i.e., all commits that affect directory1. If instead, you want to create a repository just for the contents of directoryToKeep, just skip the last step of the preparation of the source repository.

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Reducing file size of a PDF on Mac OS

The file size of PDFs can become quite large, especially when scanning documents or documents containing images. Instead of sending large files, it is almost always recommended to reduce the file size. To do that, there are several ways. For example, there is an app called PDF Squeezer in the Mac App Store (€3.59 or $3.99).

The same functionality can be achieved using Quartz filters in the ColorSync Utility. There is already one called “Reduce File Size” but it might lead to a blurry PDF. You can copy this filter and adjust the settings. However, I found custom filters in the Apple Support Community that work quite well.

  • Download the filters and unpack them.
  • Move the filters to ~/Library/Filters
  • Open your PDF with ColorSync Utility
  • In the bottom, choose the appropriate filter. There are several options starting with Reduce to …
  • Click Apply
  • If you are satisfied with the result, save the file under a different file name (File > Save As).
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