How to Change config.json for Docker Mattermost Preview

Linux Docker Mattermost

These instructions show you how to change the config.json file for a Docker Mattermost Preview.

a- As root (or if you enabled non root users to manipulate docker), let’s open a shell in the docker container

docker exec -ti mattermost-preview /bin/bash

b. Update the APT db on the docker instance and install vim (needed to edit the file)

apt update
apt install vim

c. Change config_docker.json as needed

cd /mm/mattermost/config

vim config_docker.json

d. Restart the docker container

docker restart mattermost-preview

How to Change Forgotten Password on WSL (Bash for Windows)

Linux Bash Windows

So you have installed Bash for Windows, but forgot your password!! That’s easy to fix, and here’s how:

a. Find your username by running Bash for Windows and executing whoami

$ whoami

b. Change the default user to root by running the code below on a Windows command prompt (cmd.exe)

LxRun.exe /setdefaultuser root

c. Now change the password with bash -c 'passwd [user]' (also on the Windows command prompt)

bash -c 'passwd victor_m'
Enter new UNIX password:
Retype new UNIX password:
passwd: password updated successfully

d. Change the default user back to your user

LxRun.exe /setdefaultuser victor_m

e. Profit

How to Fix Sddm on Multiple Screens

Linux KDE

When running multiple screens on KDE with SDDM, your configuration will not be loaded until you actually login to the KDE desktop, so you might end up having screens out of order, or enabled/disabled when they should not be. To fix this is simple, and here’s how.

Let’s get a list of the devices name, size and position with xrandr:

$ xrandr | grep ' connected'

DP-1 connected (normal left inverted right x axis y axis)
DP-3 connected 1920x1080+1920+0 (normal left inverted right x axis y axis) 480mm x 270mm
DP-5 connected primary 1920x1080+0+0 (normal left inverted right x axis y axis) 598mm x 337mm

As you can see, on my computer I have 3x monitors:

  • DP-1 - Connected on the first port but disabled
  • DP-3 - My secondary monitor; Resolution 1920x1080; position 1920x0
  • DP-5 - My main monitor; Resolution 1920x1080; position 0x0

So we will start by adding the right configuration to /usr/share/sddm/scripts/Xsetup

$ sudo vim /usr/share/sddm/scripts/Xsetup

# Xsetup - run as root before the login dialog appears

xrandr --output DP-1 --off
xrandr --output DP-5 --mode 1920x1080 --pos 0x0 --rotate normal --output DP-3 --mode 1920x1080 --pos 1920x0 --rotate normal


  • The first line disables the monitor connected to the first port xrandr --output DP-1 --off
  • The second line sets the right dimension and position for my other two monitors

Now we need to add the config to SDDM:

$ sudo vim /etc/sddm.conf

# Xsetup script path
# A script to execute when starting the display server

And now a simple reboot will take care of the changes:

sudo reboot