Problem with KDE Look and Feel and Desktop Theme page empty in KDE System Settings (Ubuntu-based distro)

If you're experiencing empty page of KDE Look and Feel and Desktop Theme (mine from KDE Neon beta), please do these steps:

sudo apt update
sudo apt dist-upgrade
sudo apt install qml-module-org-kde-kcm

It should work.

That's all there is to it.

Setup SSL for Jira

How to do it...

Perform the following steps to import an SSL certificate:

1. Open up a command window and go to the directory where the certificate file
resides.

2. Generate a Java KeyStore (JKS) for JIRA by running the

keytool -genkey -alias jira -keyalg RSA -keystore /opt/jks/jira.jks

3. Import the certificate into KeyStore repository
keytool -import -alias jira -keystore JIRA_INSTALL/jira.jks -file file.crt

where file.crt is the certificate file.

4. Open the server.xml file located in the /opt/atlassian/jira/conf directory in a text editor.

5. Locate and uncomment the following XML configuration snippet:

maxThreads="150"
minSpareThreads="25" maxSpareThreads="75"
enableLookups="false"
disableUploadTimeout="true"
acceptCount="100" scheme="https" secure="true"
clientAuth="false"
sslProtocol="TLS" useBodyEncodingForURI="true"
keystoreFile="/opt/jks/jira.jks"
keystorePass="mypassword"
keyAlias="jira"
keystoreType="JKS"/>




Letsencrypt

Install certbot ppa:

sudo add-apt-repository ppa:certbot/certbot

then install certbot:
sudo apt install certbot


 run certbot for manual installation of letsencrypt using challenge via DNS:

sudo certbot certonly --manual --preferred-challenges dns

openssl pkcs12 -export -in fullchain1.pem -inkey privkey1.pem -out cert_and_key.p12 -name tomcat -CAfile chain1.pem -caname root

keytool -importkeystore -srcstorepass ppz2017 -deststorepass ppz2017 

-destkeypass ppz2017 -srckeystore jira.siza.my/cert_and_key.p12 

-srcstoretype PKCS12 -alias tomcat 

-keystore jira.jks

TO see what contains in the keystore:

keytool -list -keystore /opt/jks/jira.jks

6. Restart JIRA to apply the changes.
sudo systemctl stop jira
sudo systemctl start jira

Navigate through bash history with page up/down key

Linux bash history with Page up / Page down

In linux you can configure the pgup/pgdown keys to navigate through commands you typed that begin with the string you just typed. Type "mysql" and then hit "Page up", and you will see nothing but mysql-related commands.

Unfortunately this has to be configured anew on every machine or server/vm I work on, and I always forget where this is configured (and it takes a while to find it in google), so I thought I should write it down.

In /etc/inputrc, uncomment:

# alternate mappings for "page up" and "page down" to search the history
"\e[5~": history-search-backward
"\e[6~": history-search-forward

Restart your shell or use Ctrl+X, Ctrl+R to tell it to re-read.
(thanks stackoverflow)

Yep, it's not ".bashrc" but "inputrc". Not sure why this one is not hidden, but so it is. You could try ~/.inputrc for a local, user-specific configuration.

Tried this in Ubuntu, and it works.

And I tried it in kde-neon and it works.

Credit goes to Andreas Hennings aka "donquixote". Visit his page about this here

Error mounting NFS volume

If you got error to mount NFS volume in CentOS like below:

#mount -t nfs  10.12.1.23:/volume1/test  /mnt/test                                             
mount: wrong fs type, bad option, bad superblock on 10.12.1.230:/volume1/test,
       missing codepage or helper program, or other error
       (for several filesystems (e.g. nfs, cifs) you might
       need a /sbin/mount. helper program)

       In some cases useful info is found in syslog - try
       dmesg | tail or so.




To solve this problem, you need to install nfs-utils package:

#yum install nfs-utils

In debian-based distros, you can try install nfs-common package:

#apt install nfs-common


That's all there is to it!

Have fun :)

perl: warning: Setting locale failed.

If you have error like the following:

perl: warning: Setting locale failed.
perl: warning: Please check that your locale settings:
        LANGUAGE = "en_US:en",
        LC_ALL = (unset),
        LC_MONETARY = "ms_MY.UTF-8",
        LC_ADDRESS = "ms_MY.UTF-8",
        LC_TELEPHONE = "ms_MY.UTF-8",
        LC_NAME = "ms_MY.UTF-8",
        LC_MEASUREMENT = "ms_MY.UTF-8",
        LC_IDENTIFICATION = "ms_MY.UTF-8",
        LC_NUMERIC = "ms_MY.UTF-8",
        LC_PAPER = "ms_MY.UTF-8",
        LANG = "en_US.UTF-8"
    are supported and installed on your system.
perl: warning: Falling back to a fallback locale ("en_US.UTF-8").
perl: warning: Setting locale failed.
perl: warning: Please check that your locale settings:
        LANGUAGE = "en_US:en",
        LC_ALL = (unset),
        LC_MONETARY = "ms_MY.UTF-8",
        LC_ADDRESS = "ms_MY.UTF-8",
        LC_TELEPHONE = "ms_MY.UTF-8",
        LC_NAME = "ms_MY.UTF-8",
        LC_MEASUREMENT = "ms_MY.UTF-8",
        LC_IDENTIFICATION = "ms_MY.UTF-8",
        LC_NUMERIC = "ms_MY.UTF-8",
        LC_PAPER = "ms_MY.UTF-8",
        LANG = "en_US.UTF-8"
    are supported and installed on your system.
perl: warning: Falling back to a fallback locale ("en_US.UTF-8").


The solution is to run this command:


sudo locale-gen en_US en_US.UTF-8 ms_MY ms_MY.UTF-8


The output :

Generating locales (this might take a while)...
  en_US.ISO-8859-1... done
  en_US.UTF-8... done
  ms_MY.ISO-8859-1... done
  ms_MY.UTF-8... done
Generation complete.



Run the command that produce the error. The error should not appear again.


That's all there is to it. Have fun!

KDE desktop with no taskbar

Depending on the cause of this issue in your case, you may be able to fix it by editing your plasma-org.kde.plasma.desktop-appletsrc file and then performing

kquitapp plasmashell && kstart plasmashell

One cause I've run into is the buggy multimonitor functionality sometimes "losing" the taskbar from my laptop screen after I've connected to an external monitor and later disconnected (this was in plasma 5.5 or 5.6, I think). In this scenario, I've found the problem to be the lastScreen setting in the taskbar configuration. To fix this, find the section of text in plasma-org.kde.plasma.desktop-appletsrc that looks like:

[Containments][1]
activityId=
formfactor=2
immutability=1
lastScreen=1
location=4
plugin=org.kde.panel
wallpaperplugin=org.kde.image

(Some of these lines may vary in your configuration. In mine, this section was only a dozen lines down in the file, but I have no idea how much that may vary.)

Setting lastscreen=0 fixed the problem for me. I assume that 0 represents my laptop screen, and 1 is the external monitor.

If in doubt, you can always perform the procedure in jozxyqk's answer, and compare the newly generated plasma-org.kde.plasma.desktop-appletsrc with your saved plasma-org.kde.plasma.desktop-appletsrc.bak before restoring an edited version of your saved copy.

Using bluetooth headset on Linux

I bought a bluetooth headset recently. I got to make it work with my Linux laptop. There are 2 tools that I found useful in my experience in making it works such as:

1. rfkill - let you know whether particular feature is blocked or not

Example: rfkill list

0: phy0: Wireless LAN

        Soft blocked: no

        Hard blocked: no

1: asus-wlan: Wireless LAN

        Soft blocked: no

        Hard blocked: no

2: asus-bluetooth: Bluetooth

        Soft blocked: yes

        Hard blocked: no

As you can see, the bluetooth is soft blocked. It means, you have to turn it on using software. Usually you can enable it using a GUI tool in your KDE or GNOME desktop. If it is hard blocked, it means you have to turn it on by pressing a combination of or a key on your keyboard or a switch. 

2. pavucontrol

Taken verbatim from here:

Pulseaudio volume control (pavucontrol) is a simple gtk+ based volume control tool (mixer) for the pulseaudio sound server. in contrast to classic mixer tools this one allows you to control both the volume of hardware devices and of each playback stream separately. it also allows you to redirect a playback stream to another output device without interrupting playback.

It is a powerful tool to control your input and output devices. If you want to use your bluetooth headset, you can change it here (see picture above).

That's all there is to it. Have fun!