24. March 2017

How to start Wireshark on openSUSE

The simple way how to start Wireshark on Linux is to type:

wireshark

If you run this command as a normal user you won’t be able to capture packets. In order to dump packets, you need to execute it as root. This must be done in a specific way. If try just sudo you’ll end up with interesting errors like:

Attempt #1

$ sudo su
# wireshark
QXcbConnection: Could not connect to display 
Aborted (core dumped)

Attempt #2

$ sudo wireshark
QXcbConnection: Could not connect to display 
[1]    8836 abort      sudo wireshark

The proper way how to start Wireshark is by gtk-su:

xdg-su -c wireshark

13. March 2017

How to switch tabs in Konsole

Konsole has support for tabs like other terminal emulators. The question is how to switch between tabs using a keyboard.

Default keyboard shortcut is Shift + Left/Right Arrow.

If you’re used to other keyboard shortcuts like Ctrl + PgUp/PgDn which are common in Google Chrome then you can add new shortcuts easily.

Open menu Settings, select Configure Shortcuts…

Type word tab into Search field.

Find item Next tab. Click column Alternate. Click button with title None. Now you can define a keyboard shortcut. Press Ctrl + PgUp.

Find item Previous tab. Click column Alternate and button with title None. Press Ctrl + PgDown. Click OK to confirm your configuration.

Now you can enjoy new configuration. If you like this tip or you’d like some other hint about Linux let me know in the comments section bellow.

2. March 2017

How to increase font size in pgAdmin 4 on Windows

New version of pgAdmin 4 is based on QT5. When you install pgAdmin 4 on Windows computer with a high-density display you may see that letters are too small.

Solution is to send one parameter to QT engine. It will handle DPI in different way.

Open PowerShell and go to directory with pgAdmin. Then launch application with parameter:

cd "c:\Program Files\PostgreSQL\9.6\pgAdmin 4\bin"
.\pgAdmin4.exe -platform windows:dpiawareness=0

You can persist the configuration by creating qt.conf. Start PowerShell as Administrator. Go to directory with pgAdmin and create the file:

cd "c:\Program Files\PostgreSQL\9.6\pgAdmin 4\bin"
notepad qt.conf

Write there following content:

[Platforms]
WindowsArguments = dpiawareness=0

Save the file and start pgAdmin 4 and enjoy new font size.

18. February 2017

How to configure Two-Finger Scrolling in openSUSE KDE to behave the same way like Apple MacBook

Two-Finger scrolling in openSUSE – KDE has same default configuration like Windows 10 on Lenovo. This configuration came from old days when users were using only mouse to navigate on the web. When using touchpad it’s natural to expect that it would behave similarly to a tablet or Apple MacBook. Apple made the switch in the direction some time ago to make it more natural. For some reasons developers keep the old style on Linux and even on Windows. Luckily it is possible to change the configuration very easily.

Go to System Settings and click Hardware – Input Devices

Select Touchpad from left pane, Scrolling from the tabs and check option Reverse scrolling – Vertical. Then click Apply.

15. February 2017

GitHub unable to clone repository – Permission denied (publickey)

After upgrade to new version of SSH you may experience the following problem with return code 255:

Permission denied (public key).
fatal: Could not read from remote repository.

Please make sure you have the correct access rights and the repository exists.

This happened to me after upgrade from Linux Mint 17 to 18.

How to diagnose the problem?

Run following command:

ssh -v git@github.com

You will see several lines of output and one of them is typically the reason. In my case it was:

...
debug1: SSH2_MSG_NEWKEYS received
debug1: Skipping ssh-dss key ~/.ssh/id_dsa - not in PubkeyAcceptedKeyTypes
...

DSA keys were disabled in SSH 7. Solution is to generate new key with different type, for example RSA.

ssh-keygen -t rsa
cat ~/.ssh/id_rsa.pub

Replace your key at GitHub by newly generated one. You can re-run “ssh -v” command to check whether the communication was established correctly:

PTY allocation request failed on channel 0
Hi georgik! You've successfully authenticated, but GitHub does not provide shell access.
...
debug1: Exit status 1

That’s a good sign. The connection was established and now you can try to clone a repo.