10. August 2020

How to increase font size in Konsole

Konsole is a great terminal emulator that you can find in many Linux distributions. The problem with some Linux distributions is that font is too small.

To change the font open menu Settings and select Edit Current Profile…

Select Preview tab and change Text size value in the middle of the screen. Click Ok to confirm the new font..

Another option to change the font size is to press CTRL and Scroll Up/Down with mouse wheel.

The same result could be also achieved by keys CTRL and +/- keys.

16. July 2020

systemctl Failed to list units: Access denied

During the upgrade of Debian or Ubuntu server you may encounter strange failing of scripts which are restarting services.

For some reason it’s not possible to call systemcl and any operation fails with Access denied even for root.

Here is example:

systemctl list-units
Failed to list units: Access denied

The fix to this problem it is sufficient to send TERM signal to process with PID #1:

kill -TERM 1

24. July 2019

Creating Python virtualenv fails with error: Could not find a suitable TLS CA

You can create Python virtualenv using command:

virtualenv -p /usr/bin/python3 py-env3

You may encounter following strange error:

  Collecting setuptools
Exception:
Traceback (most recent call last):
  File "/usr/share/python-wheels
...
OSError: Could not find a suitable TLS CA certificate bundle, invalid path: /etc/ssl/certs/ca-certificates.crt
...
Error in sys.excepthook:
Traceback (most recent call last):
  File "/usr/lib/python3/dist-packages/apport_python_hook.py", line 145, in apport_excepthook
    os.O_WRONLY | os.O_CREAT | os.O_EXCL, 0o640), 'wb') as f:
FileNotFoundError: [Errno 2] No such file or directory: '/var/crash/_usr_bin_virtualenv.1000.crash'

The error message is not very clear. Problem is caused by ca-certificates and it could be fixed by command:

sudo update-ca-certificates

11. June 2019

How to start D-Bus in Docker container

Many Linux applications require D-Bus which is not running by default in Docker containers.

When you attempt to start the application you might get the following error:

D-Bus library appears to be incorrectly set up; failed to read machine uuid: Failed to open "/var/lib/dbus/machine-id": No such file or directory
See the manual page for dbus-uuidgen to correct this issue.
  D-Bus not built with -rdynamic so unable to print a backtrace
Aborted

First of all you need to generate missing machine-id by command:

dbus-uuidgen > /var/lib/dbus/machine-id

The application will be able to start even when the daemon is not running.

To start the D-Bus daemon inside the container you need to run following command on Ubuntu, Centos 7, Centos 8:

mkdir -p /var/run/dbus
dbus-daemon --config-file=/usr/share/dbus-1/system.conf --print-address

Command on Centos 6:

dbus-daemon --config-file=/etc/dbus-1/system.conf --print-address

Now the daemon is running and your application should be able to start. The output should look like this:

unix:path=/var/run/dbus/system_bus_socket,guid=9cfabcc6f66027251e092e955d09e707

27. April 2019

How to start TigetVNC server on port 5900

When you start TigerVNC server by following command:

vncserver

then it will automatically bind to port 5901.

When you want to start the server on 5900 then you need to type following command:

vncserver :0

This looks a little bit mysterious, but if you dig through the documentation you might find that there is the following mapping:

:0 -> 5900
:1 -> 5901
:2 -> 5902
:3 -> 5903
...

Now it’s clear that when you omit the parameter, it will default to code :1 which is mapped to the port 5901.