How to encrypt and decrypt GPG mails in the terminal

Encrypting

gpg -e -a -r <receiver@email.address> [-r <receiver2@email.address>]
<type message>
<ctrl d>

Now copy the PGP message to your mail client and send that mail.

  • You need one -r flag per receiver address
  • With a single receiver, you can also write gpg -ear reci@pie.nt

Decrypting

gpg -d
<paste encrypted message>
<ctrl d>

Adding public keys

gpg --keyserver keyserver.ubuntu.com --search-keys <user@domain.com>
<number of the search result that should be imported>

Also see [Using GPG/PG...

How to fix huge buttons in Zoom

If you're running Ubuntu Mate and your Zoom suddenly has huge buttons, it might assume you're using a very High DPI display. While this is usually a good idea, the heuristic determining whether to enable this HiDPI mode or not does not work perfectly with Ubuntu Mate and multiple displays.

Force a specific scale factor

Unfortunately, this setting is not exposed in the GUI, you'll have to change the config file.

First, make sure zoom is closed completely, i.e. there should not be a zoom icon in the panel next to the clock.

Open `~/.conf...

Debugging microphone issues in Linux and Zoom

Testing

Since Zoom does some post-processing of your audio input, it's best to hear yourself in a Zoom recording:

  • Open a Zoom meeting for yourself.
  • Choose "Record to this computer" in the Zoom toolbar.
  • Speak some words (quiet and loud) and allow some seconds of silence.
  • End the meeting.
  • Zoom will open a folder with an audio recording.
  • Listen to the audio recording.

Check microphone settings in Linux

Right-Click on the speaker icon in your tray, then go to Sound Preferences => Input.

Selecting the correct microphone...

Zoom: Fix gray shadow during screen sharing

When sharing a screen over Zoom in Ubuntu MATE, you might notice a dark gray shade.

This shade is caused by the Compton compositing manager, which you probably enabled in MATE Tweak / Windows / Window manager. Zoom draws a green rectangle around your screen to indicate what is being shared, and Compton draws a "shadow" into this rectangle.

Emergency fix

If this happens to you during a meeting, you can quickly "fix" it by stopping Compton from the console:

killall compton

The shado...

What to do when your GPG/PGP key expires

Your GPG client notified you that your keypair will soon expire, or has already expired. Here is what to do.

Are you using Thunderbird?

If you're using the built-in GPG encryption in Thunderbird 78+, you can extend your key from the Thunderbird key manager.

Suggested way: Extend your key expiry

  1. Find the ID of the expiring key, e.g. with ...

GPG: Extract private key and import on different machine

After extending the expiry date of a GPG key you might have to copy your key to another machine to use the same key there. Here is how:

  1. Identify your private key:

    gpg --list-secret-keys user@example.com
    

    Example output:

    pub   4096R/ABC12345 2020-01-01 [expires: 2025-12-31]
    uid                  Your Name <user@example.com>
    sub   4096R/DEF67890 2020-01-01 [expires: 2025-12-31]
    

    Remember the ID of your key (second column, after the slash, e.g. "ABC12345"). If you have a "sub" entry, you can ignore it.

2....

ThinkPad Fix: Touchpad-Scrollen funktioniert nicht nach suspend

Mir ist aufgefallen, dass nach dem Aussetzen meines Notebooks das Scrollen auf dem Touchpad (am Rand oder mit zwei Fingern) nicht mehr funktioniert. Dies scheint ein bekannter Bug zu sein

Mein setup ist:

  • ThinkPad T480
  • Ubuntu MATE 18.04

Der verlinkte Kommentar von oben hat mir dabei geholfen, das Problem zu lösen:

Du musst die Dabei /etc/default/grub (sudo!) bearbeiten und diese Zeile ändern:

# von:

GRUB_CMDLINE_LINUX_DEFAULT="quiet splash"

# zu:

G...

Wenn Anhänge und Kalendereinladungen als winmail.dat erscheinen

Wenn eine eingehende E-Mail eine einzelne Anlage mit dem Namen winmail.dat enthält, hat ein Windows-Benutzer seinen Outlook-Client falsch konfiguriert. Wahrscheinlich versucht er, dir einen Anhang oder eine Kalendereinladung zu senden, die nun in einem proprietary Format in den winmail.dat-Anhang komprimiert werden. Outlook hängt auch eine winmail.dat an, wenn ein solcher Benutzer eine formatierte E-Mail geschrieben hat.

Bitte den Absender, seine Outlook Einstellung zu fixen

Wenn möglich, bitte de...

Wie man eine feste Mikrofonquelle in Ubuntu einstellt, wenn sie sich ständig ändert

Unter bestimmten Umständen ist es möglich, dass Ubuntu das Standardmikrofon selbständig umschaltet, z.B. wenn du ein Headset verwendest, das über einen 3,5mm-Stecker angeschlossen ist, und deine USB-Webcam ebenfalls ein Mikrofon hat, könnte Ubuntu das Standardmikrofon auf das USB-Mikrofon der Webcam setzen.

Wenn du das nicht willst, ist es erstaunlich schwer, Ubuntu davon abzubringen. Hier ist wie.

Alternativ kannst du auch alle Geräte außer dem gewünschten deaktivieren. Beachte, dass dies nicht...

How to avoid 100% CPU load when screen-sharing through zoom

Zoom is a video conference tool that has great screen-sharing support on Linux. [1]
However, Zoom's screen sharing causes immense CPU load, slowing down other applications, and on laptops the CPU fan going at full speed will drive you insane.

To fix that, open Zoom's settings dialog (cog icon in the top right), and in the "General" section set the "Limit your screen share to X frames per second" option.
I suggest you set to 4 FPS. This may sound very low but is actually enough for pair programming or demoing something.

...

Useful Zoom shortcuts

| alt + q | End Meeting ("quit") |
| alt + a | Toggle Mute ("audio") |
| alt + s | Share Screen ("share") |
| alt + i | Open invite menu ("invite") |

For more shortcuts see the zoom help.

Snom VOIP phone shows your own name instead of the incoming number

This is because of how Sipgate sends the incoming caller ID. As it is intended, it shows both who the call is for (in case you have multiple numbers configured on your phone) and who it's from, after a line break. Neither SNOM phones nor linphone, ekiga, etc handle this perfectly. You may either fix this only on your SNOM phone or on all connected clients:

SNOM phone fix only

  • Log into the web interface of your phone (yes, your phone has a web server) by opening its IP address in a browser. You can find the IP address in the phone'...

Ensure screen lock on suspend

Ubuntu Mate 18.04 has a bug in which suspending your computer does not lock your screen in every case. If closing your laptop's lid or clicking the suspend menu option in your top right menu already locks the screen, you're not affected and don't need to do anything.

Step 1

To make sure screen lock is engaged when you suspend your computer, please create the following file, as root:

/etc/systemd/system/lock.service

[Unit]
Description="Make extra sure to lock the screen when suspending"

[Service]
Type=oneshot
User=root
...

Präsentieren unter Linux: Bildschirmspiegelung mit inkompatiblen Projektorauflösungen

Wenn du mit einem Projektor präsentierst, möchtest du wahrscheinlich deinen Bildschirm spiegeln. Auf diese Weise zeigen der Laptop und der Projektor das gleiche Bild.

Dein Linux-Anzeigedialog enthält normalerweise ein Kontrollkästchen zum Spiegeln von Bildschirmen. Wenn du dieses Kontrollkästchen aktivierst, kann sich die Anzahl der verfügbaren Auflösungen jedoch drastisch verringern. Dies wird durch inkompatible Listen der verfügbaren Auflösungen zwischen den beiden Bildschirmen verursacht. Oft hast du dann eine sehr niedrige gemeinsame Au...

HowTo install Ubuntu's HWE stack for more recent kernel and grahpics drivers

With the latest hardware on both Laptops and Desktop computers, it might be necessary to install more recent hardware drivers, i.e. Linux kernels and xorg versions.

While it's possible to use backports from various sources on the internet, it's neither very safe nor tested very well. However, there is official support for the Hardware Enablement Stack in Ubuntu LTS-Versions, i.e. 16.04 and 18.04.

If your system is working fine without the HWE packages installed, it's best to just leave it alone. If you're sure issues on your s...

What to do when your Dell U2410 monitor fails to power on

Dell U2410 screens have a stupid firmware bug where when you manually switch off the monitor and then your computer, the screen will no longer power on when the computer is restarted. In such a case the power button is dead and no longer reacts to input.

In order to fix this:

  • Remove the power cable from the monitor
  • Wait for 10 minutes
  • Replug the power cable

Seriously.

Take care with dates in English e-mails

The English speaking world does not agree on how to write dates. For the 21st of June, Americans use "06/21/2018", while the British use "21/06/2018".

To avoid confusion, prefer to write either "June 21, 2018" (which is American English), or "21 June 2018" (which is British), but which cannot be misinterpreted.

Configure CSipSimple for Sipgate

The default settings used by the wizard did not work for me. I got authentication errors all the time.

This is what worked for me:

Account name: Sipgate.de
SIP-IP:       Your Sipgate ID (see https://secure.live.sipgate.de/settings/phone/, click on phone and select "Show SIP credentials")
SIP-Passwod:  You Sipgate password (see link above)
SIP Server:   sipgate.de:5060
Proxy:        proxy.live.sipgate.de

If you have trouble with CSipSimple, try [Zoiper](https://makandracards.com/makandra-orga/4...

How to change your dm-crypt passphrase

dm-crypt has multiple passphrase slots. The process will be to add a new passphrase to a new slot, check that it works, and then remove the old passphrase.

  1. Find out which partitions are decrypted by dm-crypt:
$ lsblk --fs
NAME                  FSTYPE      LABEL   UUID                                   FSAVAIL FSUSE% MOUNTPOINT
nvme0n1                                                                                         
├─nvme0n1p1           vfat                65CB-0937                               503,2M     2% /boot/ef...

Erstelle ein neues SSH-Schlüsselpaar

Wir verwenden SSH-Schlüssel für die Authentifizierung gegenüber unseren Servern. Wir verwenden niemals eine passwortbasierte Authentifizierung. Unsere SSH-Schlüssel sind mit einem Passwort verschlüsselt, um einen zweiten Faktor für die Authentifizierung zu erfordern, falls ein Schlüssel kompromittiert wird.

Bevor du beginnst, lege in KeePass einen neuen Eintrag für deinen SSH-Schlüssel an und erstelle ein neues Passwort. Siehe die Sicherheitsrichtlinien für Passw...

Thunderbird: Don't automatically mark messages as read and as junk in Thunderbird

  • Preferences -> Display -> Advanced (tab not button)
  • If the option "Automatically mark messages as read" has the suboptions "Immediately on display" and "After .... seconds", you can uncheck the checkbox. It won't mark new mails as read anymore.

for older thunderbird versions:

(see attachment)

  • menu -> "preferences" -> "preferences" -> "Display" -> "Advanced" tab
  • uncheck "Automatically mark messages as read".
  • close settings
  • to mark emails as read click the tiny green circle in the list vi...