tl;dr

The summary of all the following is roughly this:

• Remove or move the directory /usr/share/help/C/gnome-help.
• Run the command sudo apt reinstall gnome-user-docs gnome-getting-started-docs ubuntu-docs.
• The missing directory and its contents must come back.

This works OK in one of my 20.04 system, but not on another 20.04 system. Both systems are up-to-date.

I want to find out what makes this difference.

After upgrading from 19.10 to 20.04 the GNOME Help application (yelp) cannot find GNOME help files. For example, when I am in the GNOME Files application (nautilus) and press F1 I get the following error message in the yelp window:

Document Not Found
The URI ‘help:gnome-help/files’ does not point to a valid page.

The same thing occurs in other GNOME applications, like gedit, gnome-calculator etc.

yelp can display the man pages OK. The problem is only with the "help" pages. Is there any package that needs to be installed?

I tried to install package gnome-user-guide, but it didn't help. Packages:

gnome-getting-started-docs
gnome-user-docs
ubuntu-docs
xorg-docs-core

are already installed and up-to-date.

It seems* that the files needed are the ones under /usr/share/help/C/gnome-help/ and the package gnome-user-docs is the one that provides these (https://packages.ubuntu.com/focal/all/gnome-user-docs/filelist). However, even removing, purging and re-installing this package does not bring these files to my system.

*Note: dpkg -S /usr/share/help/C/gnome-help/files.page output is this:

gnome-user-docs: /usr/share/help/C/gnome-help/files.page

Also ls -lisad /usr/share/help/ /usr/share/help/C output is:

8651957 4 drwxr-xr-x 59 root root 4096 May 14 19:55 /usr/share/help/
8651631 4 drwxr-xr-x 31 root root 4096 May 17 17:39 /usr/share/help/C

and permissions and ownership of the files within these directories is -rw-r--r-- root root.

Similarly, other GNOME packages (for example, gnome-calculator) when (re)installed, they do not populate the relevant directory under /usr/share/help/C/.

I tested by copying /usr/share/help/C/gnome-help/ directory and its contents from another system and then reinstalling the gnome-user-docs package. The re-installation deleted the necessary files which I just copied there! Before doing the re-installation, but after copying these files manually, yelp was able to display its home screen and the relevant help screens OK. After the re-installation, the above mentioned problem occurs.

I have tried with various locales with the installation of gnome-user-docs package. Every time the same thing occurs. The files that I copied manually under /usr/share/help/C/ are being deleted:

# LANG=en_US.UTF-8 apt --reinstall install gnome-user-docs
# LANG=en_GB.UTF-8 apt --reinstall install gnome-user-docs
# LANG=C.UTF-8     apt --reinstall install gnome-user-docs

My locale output is this:

LANG=C.UTF-8
LANGUAGE=
LC_CTYPE="C.UTF-8"
LC_NUMERIC=en_GB.UTF-8
LC_TIME=en_GB.UTF-8
LC_COLLATE="C.UTF-8"
LC_MONETARY=en_GB.UTF-8
LC_MESSAGES="C.UTF-8"
LC_PAPER=en_GB.UTF-8
LC_NAME=en_GB.UTF-8
LC_ADDRESS=en_GB.UTF-8
LC_TELEPHONE=en_GB.UTF-8
LC_MEASUREMENT=en_GB.UTF-8
LC_IDENTIFICATION=en_GB.UTF-8
LC_ALL=

(Note that I tested with LANG=en_US.UTF-8 also; result was the same.)

The output of check-language-support --show-installed is:

firefox-locale-en gimp-help-en hunspell-en-au hunspell-en-ca hunspell-en-gb hunspell-en-us hunspell-en-za hyphen-en-ca hyphen-en-gb hyphen-en-us language-pack-en language-pack-gnome-en libreoffice-help-en-gb libreoffice-help-en-us libreoffice-l10n-en-gb libreoffice-l10n-en-za mythes-en-au mythes-en-us poppler-data thunderbird-locale-en thunderbird-locale-en-gb thunderbird-locale-en-us wamerican wbritish

Currently installed packages:

# apt --installed list | grep -i "docs"

gnome-getting-started-docs/focal,focal,now 3.36.1-0ubuntu1 all [installed]
gnome-user-docs/focal,focal,now 3.36.1-0ubuntu1 all [installed]
ubuntu-docs/focal,focal,now 20.04.2 all [installed]
xorg-docs-core/focal,focal,now 1:1.7.1-1.1 all [installed,automatic]

More Information

(1)

The output of sudo apt-cache depends yelp is like this:

yelp
  Depends: libc6
  Depends: libglib2.0-0
  Depends: libgtk-3-0
  Depends: libwebkit2gtk-4.0-37
  Depends: libyelp0
 |Depends: dconf-gsettings-backend
  Depends: <gsettings-backend>
    dconf-gsettings-backend
  Depends: python3-distro
  Depends: yelp-xsl
  Depends: man-db
    man-db:i386
  Recommends: docbook-xml

Note: This is the same output as on another system which does not have this problem.

(2)

The checksums for the yelp package are OK:

$ debsums yelp | wc -l
230
$ debsums yelp | grep 'OK$' | wc -l
230
$ debsums -a yelp | grep 'OK$' | wc -l
230

However, the checksums for the gnome-user-docs package show inconsistent results. On the system with this problem:

$ debsums gnome-user-docs | wc -l
4
$ debsums gnome-user-docs | grep 'OK$' | wc -l
4
$ debsums -a gnome-user-docs | grep 'OK$' | wc -l
4
$ debsums gnome-user-docs
/usr/share/doc/gnome-user-docs/NEWS.gz                                        OK
/usr/share/doc/gnome-user-docs/README                                         OK
/usr/share/doc/gnome-user-docs/changelog.Debian.gz                            OK
/usr/share/doc/gnome-user-docs/copyright                                      OK

Whereas on a system without this problem:

$ debsums gnome-user-docs | wc -l
465

and the difference is in the /usr/share/help/C/gnome-help/ and /usr/share/help/C/system-admin-guide/ files: The files I am talking about throughout this post.

I switched from MacOS to Ubuntu this weekend .

I'm used to a functionality I had with MacOS I want for all my apps in Ubuntu.

For any app in MacOS, you can search through the different commands within the app thanks to their names, as follow:

Here for instance, I searched for Close a tab in Chrome. Furthermore, Chrome gives me what is the corresponding shortcut for what I search, if it exists, and where it is in the different panes.

How can I add it to all my Ubuntu apps?

For instance, in LibreOffice Writer, I wanted to search for rounding corners of an image, but I couldn't find it thanks to the app.

I have LibreOffice 6.2.2.2 installed as a Flatpak. Everything works fine but when I go to the menu Help -> LibreOffice Help I get the message:

LibreOffice Help Not Installed

How can I install the offline help for the Flatpak LibreOffice?

I managed to download the help package there: http://download.documentfoundation.org/libreoffice/stable/6.2.2/deb/x86_64/LibreOffice_6.2.2_Linux_x86-64_deb_helppack_en-US.tar.gz (link found on the LibreOffice download page https://www.libreoffice.org/download).

The help package contains subfolders /opt/libreoffice6.2/help/en-US/ and /opt/libreoffice6.2/help/media/ with *.html help files and some other *.js files.

Is there a way one can use this package to install the offline help for the Flatpak LibreOffice installation?

PS: I'm aware that I need the help version for the corresponding LibreOffice version, and that the help language must match the LibreOffice UI language.

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

  

• Scrollkeeper - shows empty page:

  

• 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

  

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

I have both Ubuntu 16.04 LTS and Ubuntu 18.04 LTS installed.

I want to search for documentation and read it off-line (as it is included to the installed packages in /usr/share/help and other locations). As far I can understand it has three formats:

• HTML - .page (dpkg -S .page | grep -E /usr/share/help | awk '{print $1}' | sort | uniq | wc -l returns 12 results)
• DocBook - .docbook (dpkg -S .docbook | grep -E /usr/share/help | awk '{print $1}' | sort | uniq | wc -l returns 21 results)
• ManPage (many from manpath = /usr/local/man:/usr/local/share/man:/usr/share/man)

These files are rendered by Yelp program (from yelp package) with executables yelp and gnome-help.

Notes:

1. here on AskUbuntu was similar question about ScrollKeeper database (provided by rarian-compat package) without answer;

2. there is a bug 726439 named "Search for document returns an Unknown error: 'URI xref:search=' could not be parsed" on LauchPad.net (from 2011 year) about broken(?) search in Yelp. If I press CtrlS to search searchterm in current version of Yelp it still returns

   Unknown Error
   The URI ‘xref:search=searchterm’ could not be parsed.

Of course I can run the grep over all these files, but is it possible to run such search from Yelp?