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I have installed the Dolphin file manager under Ubuntu 18.04/Gnome (with apt install). It doesn't show thumbnails for any file, neither in the folder nor in the information panel (to the right). See screenshot. How can I fix it?

enter image description here

Also, in the Dolphin Preferences I noticed that under General > Previews > Show previews for: there is a blank list, which I am not allowed to edit. I believe I should have a list of file types there. See screenshot.

enter image description here

I have tried deleting the content of ~/.cache/icon-cache.kcache and ~/.cache/thumbnails.tar, then logging out and in again, but no change.

I also tried the fix that should address video clip thumbnails, but got an error in the process:

-> sudo apt install ffmpegthumbs mplayerthumbs kffmpegthumbnailer
[sudo] password for fanta: 
Reading package lists... Done
Building dependency tree       
Reading state information... Done
Package mplayerthumbs is not available, but is referred to by another package.
This may mean that the package is missing, has been obsoleted, or
is only available from another source

E: Package 'mplayerthumbs' has no installation candidate

Note the issue is not limited to thumbnails of video clips, it applies to all files, including images (Jpeg, PNG, etc.).

Update: I have tried adding the KDE Plasma repository

deb http://archive.neon.kde.org/user bionic main

then run a sudo apt upgrade and re-booted. I didn't actually install KDE Plasma. Now the thumbnails are working, but I am getting other malfunctions, including the Software & Updates app that doesn't start (software-properties-gtk issues "aptsources.distro.NoDistroTemplateException: Error: could not find a distribution template for neon/bionic"). Therefore I am undoing the changes.

  • See askubuntu.com/questions/411891/dolphin-does-not-show-thumbnails. If that older Q&A doesn't solve your issue, please update the question. – Justice for Monica Sep 3 at 8:46
  • @DKBose I have tried the fix from the older post you mention, which addresses video thumbnails only, and got an error. Updated my issue with the information. – Fanta Sep 3 at 9:54
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    I just checked my Ubuntu 18.04 with Dolphin installed. I can see previews of .jpg and .png file and a .webm video file. The panel which is blank in your case, is populated with entries for me. So I don't know what's missing in your case. – Justice for Monica Sep 3 at 10:20
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    Please try installing kio-extras and kio-extras-data. I assume you already have ffmpegthumbs and kdegraphics-thumbnailers installed. Log out and log in again. Do things work? – Justice for Monica Sep 3 at 10:36
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    After re-installing Ubuntu 18.04, I have installed dolphin, kio-extras and kio-extras-data, as per your recommendation. Dolphin now shows thumbnails, and the related file types are listed in Dolphin Previews Preferences. – Fanta Sep 4 at 5:25
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In Dolphin does not show thumbnails from 2014, the following additional packages are recommended:

  • ffmpegthumbs: video thumbnail generator using ffmpeg
  • mplayerthumbs: video thumbnail generator using mplayer (no longer needed and not in the bionic repos)
  • kffmpegthumbnailer: video thumbnailer for KDE (doesn't appear necessary in KDE Plasma5)

A more recent answer from 2016 there indicates that kio-extras is also needed.


I had recently installed dolphin on Ubuntu 18.04 and could view thumbnails and also had the Show Previews pane that was missing on your system.

I looked through the appropriate history.log file in /var/log/apt to see what thumbnail-related packages were installed along with dolphin. I found two:

  • ffmpegthumbs and
  • kdegraphics-thumbnailers

Indeed, these were the only two packages with "thumb" in their names on my system:

$ apt list --installed | grep -i thumb

WARNING: apt does not have a stable CLI interface. Use with caution in scripts.

ffmpegthumbs/bionic,now 4:17.12.3-0ubuntu1 amd64 [installed,automatic]
kdegraphics-thumbnailers/bionic,now 4:17.12.3-0ubuntu1 amd64 [installed,automatic]
$ 

kio-extras, the package recommended by the second answer, along with kio-extras-data, was installed on my system, not along with dolphin but when I installed gwenview, Kubuntu's image viewer.

Anyway, this is what dolphin looks like:

Dolphin showing thumbnails and the pane to select which previews are shown

Dolphin with thumbnails and preview pane


Edit:

kio-extras is a "recommends" for dolphin in Kubuntu 19.04.

  • Thanks, the Previews Preferences not appear in antiX 19 (Buster 10), with this kio-extras working fine – Indacochea Wachín Oct 21 at 11:04

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