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.

9. February 2017

Courier Mail Server stops delivering emails after upgrade to 0.76

It might seem like a minor upgrade to go from version 0.75 to 0.76. In the case of Courier Mail Server, it’s a huge change in the orchestration of services.

Courier Mail Server has a very good modular architecture which allows independent control of each aspect of mail delivery. You can separately restart or change each service like MTA, POP or IMAP. Even encrypted variants of servers are available as separate services. The version 0.76 is pushing it even further in the fashion of micro services.

There is new service ‘courier’ which is responsible for scheduling mail delivery after mail was accepted via SMTP or SMTP-SSL. If you’re not aware of this new service you might wonder why is Courier not logging any activity after accepting email. Just make sure that service is running. You can start it by:

service courier start

After the start of the service, you may see that emails are being processed, but they’re not delivered to local mail users. In the log, you can find many error messages like:

/usr/bin/maildrop: Unable to change to home directory.

The other major change is the switch from courier-maildrop to common maildrop. That might seem like a minor change, but it could render your server completely useless. Emails won’t be simply delivered to user’s mailbox:

/usr/bin/maildrop: Unable to change to home directory.

The problem is that maildrop is accepting different parameters than courier-maildrop. Package maintainers recommends to change line with maildrop in /etc/courier/esmtpd from:

DEFAULTDELIVERY='|/usr/bin/maildrop'

to:

DEFAULTDELIVERY='|/usr/bin/maildrop -w 90 -V 1 -d ""'

If you do not have time to play with maildrop, you can change to default configuration:

DEFAULTDELIVERY=./Maildir

Here is the explanation of changes from package maintainers (click image for detail):

Restart services and delivery should start. It might happen that services do not shut down, because upgrade changed user from ‘daemon‘ to ‘courier‘. Then the solution is to terminate services by:

pkill -9 -f courier

Then you can start services and everything should work ok.