I have Ubuntu 18.04 LTS installed.

I want to search for documentation and read it off-line (as it is included to the installed packages).

Yelp does not work for this purpose.

So I tried to use KHelpCenter. I installed it with sudo apt install khelpcenter.

When I started it, it have various information sources:

  • KDE-related stuff
  • UNIX manual pages - renders with error:

    The requested operation could not be completed
    Cannot Initiate the man Protocol
    Technical Reason: Unable to Create io-slave

    man protocol error in khelpcenter

  • Scrollkeeper - shows empty page:

    scrollkeeper empty page in khelpcenter

  • Browse Info Pages - renders with error:

    The requested operation could not be completed
    Cannot Initiate the info Protocol
    Technical Reason: Unable to Create io-slave

    info page error in khelpcenter

How to fix all these errors? Do I need to install some dependency or configure already installed?


Problems with info: and man: links are gone after installation of these packages (idea from this answer):

sudo apt-get install kinit kio kio-extras kded5

Then we need to install Oxygen theme to have nice look-and-feel:

sudo apt-get install plasma-theme-oxygen oxygen-icon-theme

To remove warning kf5.kservice.services: KServiceTypeTrader: serviceType "QImageIOPlugins" not found we need to install other package:

sudo apt-get install libkf5kdelibs4support-data

As the result we will be able to search on 18.04 LTS in Application Manuals (KDE-documentation) and man-pages.

KHelpCenter internally use ScrollKeeper's component scrollkeeper-get-content-list (located in rarian-compat package), so we need to install it:

sudo apt-get install rarian-compat

To add content to Scrollkeeper category we need to install some application which has documentation in /usr/share/omf:

 sudo apt-get install synaptic diffuse

But its installation does not help. ScrollKeeper category contains very small amount of objects, their pages fail to render.


  1. This instruction seems to be universal for 16.04 LTS and 18.04 LTS, but in 16.04 LTS we do not have search toolbar.
  2. On Ubuntu 14.04 LTS khelpcenter has version 4.13, works out the box but does not have search functionality. ScrollKeeper functionality is poor as in newer releases.

Conclusion: use Yelp to view desktop documentation (but without full-search).

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