I've recently came back to Ubuntu from Kubuntu, but I really like Dolphin. Is there any way how to set it up as default file manager?
6 Answers
To view the current default for opening directories:
xdg-mime query default inode/directory
To set Dolphin as default:
xdg-mime default org.kde.dolphin.desktop inode/directory
To set Thunar as default:
xdg-mime default thunar.desktop inode/directory
Run either on the terminal as regular user. If you want to set the default to another file manager, install the file manager, and find the correct .desktop file by searching in /usr/applications/ on the command-line.
Related files:
- /usr/share/applications/defaults.listsystem-wide defaults
- $HOME/.local/share/applications/mimeapps.list
- $HOME/.config/mimeapps.listwhere- xdg-mimesaves configuration
Sources:
Steps:
- Open a terminal, e.g. using Ctrl+Alt+T 
- Install - exo-utilsby running the following command in the terminal:- sudo apt-get install exo-utils
- Run the following command in the terminal: - exo-preferred-applications
- In the window that opens, click on Utilities 
- On the File Manager section, click the drop-down menu arrow + Other... 
- Find - /usr/share/applicationsdirectory
- Adjust to show all files and select - dolphin.desktop(wherever you find it)
- Click close 
 
    
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Adding to Rucent88 answer:
For me the dolphin desktop file was stored in /usr/share/applications/org.kde.dolphin.desktop. So 
xdg-mime default org.kde.dolphin.desktop inode/directory
did the trick.
Keep in mind to have a look where the desktop link is located. Have a look at the file list of your installed file manager to see how the desktop link is called if you can't find it.
 
    
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As exo-preffered-applicatiosn from exo-utils have been depreciated and moved to xfce4-settings. Use the following steps:
- Open the terminal Ctrl+Alt+T.
- Install xcfe4-settings sudo apt install xfce4-settings
- Type xfce4-mime-settingsin terminal.
- A window will appear, click on Utilities in it.
- Go to File Manager section and click on others
- Open /usr/share/applications directory and set from exectuable files to all files.
- Select for org.kde.dolphin.desktop and open it.
- Close
also it works only with:
xdg-mime default dolphin.desktop inode/directory application/x-gnome-saved-search
From: http://www.fandigital.com/2013/01/set-nemo-default-file-manager-ubuntu.html
In My, Ubuntu 20.04.2 LTS below solution worked. Not sure, is there are any consequences for this approach.
In file /usr/share/applications/defaults.list modified entry inode/directory=org.gnome.Nautilus.desktop to inode/directory=org.kde.dolphin.desktop
 
    
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