Default applications

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Reason: It would be good to have detailed explanations for other DEs as well. (Discuss in Talk:Default applications#)

There are numerous places to configure default applications on Linux. This page will attempt to address problems related to the following issues:

  • You need to change a certain default application (e.g. after switching desktop environments), but there appears to be nowhere to configure it, or an application ignores your configuration
  • You regularly switch back and forth between several desktop environments, and need to configure some applications (e.g. file manager) on a per-desktop-environment basis, but need to configure others (e.g. web browser) globally

Changing a default application

xdg-open

xdg-open is a desktop-independent tool for configuring default applications.

Exactly how it works

This is currently very shaky because the standard in question (relevant freedesktop.org document, "Default application ordering" section) is still not finalised and it is even less correctly implemented.

What happens with the current version of xdg-open (extra/xdg-utils 1.1.0rc1-3) is the following: xdg-open uses xdg-mime (among other things; if you use a mainstream DE like GNOME, KDE or LXDE, xdg-open might try using their specific tools before xdg-mime) to find the MIME type of the file that is to be opened and the default application associated with that MIME type. xdg-mime looks for the default application in the following files:

/usr/share/applications/defaults.list      (global)
~/.local/share/applications/defaults.list  (per user, overrides global)

The syntax of these files is:

[Default Applications]
mimetype=desktopfile1;desktopfile2;...;desktopfileN

E.g.

[Default Applications]
text/html=firefox.desktop;chromium.desktop

The intent is to be able to specify applications in order of preference so the next would be selected if the previous is unavailable. However, xdg-open is currently broken and specifying more than one application for a single MIME type will result in none being used. Be sure to specify only one application per MIME type.

Also see xdg-open for more information on what affects its behaviour. This information is sufficient for a user to configure default applications on Arch currently.

How it should work

However, the behaviour described in the previous section is actually wrong according to the quoted standard draft. defaults.list should only be used by distributions/DEs to specify sane defaults for that particular environment. This file should only be placed in /usr/share/applications/, it should be a system-wide setting and it should not be changed by users. Instead, users should use the files /usr/share/applications/mimeapps.list (global) and ~/.local/share/applications/mimeapps.list (per user, overrides global) to specify custom file associations. The syntax of these files is as follows:

mimeapps.list
[Added Associations]
mimetype=desktopfile1;desktopfile2;...;desktopfileN
...
[Removed Associations]
mimetype=desktopfile1;desktopfile2;...;desktopfileN

The [Added Associations] section is used to specify preferred (default) applications in decreasing order of preference for the specified MIME type. The [Removed Associations] section is used to explicitly remove any previously inherited associations.

Note that the upstream, yet unreleased xdg-utils were fixed to use mimeapps.list instead of defaults.list but the xdg-open bug (specifying multiple applications breaks it completely) still remains.

Currently, the best option is to use mimeoAUR, which implements everything explained above correctly. There is also xdg-utils-mimeoAUR which provides a patched xdg-open to use mimeo. Both are available in AUR.

Gnome 3

The xdg-open settings are usually recognized by Gnome, but if they aren't, there are still other methods.

GConf

As far as I can tell, on Gnome 3, there are two configuration systems, GConf (older) and dconf (newer). GConf can be configured with gconf-editor; in particular, you can try messing with the /desktop/gnome/applications/ key, but changing settings there didn't fix any problems I had. dconf can be configured with the gsettings command.

Terminal

To configure the default terminal for the package nautilus-open-terminal to Konsole, use

$ gsettings set org.gnome.desktop.default-applications.terminal exec konsole
$ gsettings set org.gnome.desktop.default-applications.terminal exec-arg "'-e'"

The second command tells konsole to expect a command to be passed to it as part of the invocation. nautilus-open-terminal needs this because it passes a cd command in order to switch to the appropriate directory. For example, opening a terminal in your ~/Desktop directory will invoke something like

$ konsole -e cd "~/Desktop"

Web browser

To configure the web browser used by the AUR package gnome-gmail-notifier, run

$ gconf-editor

and edit the /desktop/gnome/url-handlers/http/ key. You may want to change https/, about/, and unknown/ keys while you're at it.

Custom File Associations

The following method creates a custom mime type and file association manually. This is useful if your desktop does not have a mime type/file association editor installed. In this example, a fictional multimedia application 'foobar' will be associated with all '*.foo' files. This will be done a per user basis (as opposed to system-wide).

  • First, create the file ~/.local/share/mime/packages/application-x-foobar.xml:
$ mkdir -p ~/.local/share/mime/packages
$ cd ~/.local/share/mime/packages
$ touch application-x-foobar.xml
  • Then edit ~/.local/share/mime/packages/application-x-foobar.xml and add this text:
<?xml version="1.0" encoding="UTF-8"?>
<mime-info xmlns="http://www.freedesktop.org/standards/shared-mime-info">
	<mime-type type="application/x-foobar">
		<comment>foo file</comment>
		<icon name="application-x-foobar"/>
		<glob-deleteall/>
		<glob pattern="*.foo"/>
	</mime-type>
</mime-info>

Note that you can use any icon, including one for another application.

  • Next, edit or create the file ~/.local/share/applications/foobar.desktop to contain something like:
[Desktop Entry]
Name=Foobar
Exec=/usr/bin/foobar
MimeType=application/x-foobar
Icon=foobar
Terminal=false
Type=Application
Categories=AudioVideo;Player;Video;
Comment=

Note that Categories should be set appropriately for the application type (in this example, a multimedia app).

  • Now update the mime database with:
$ update-mime-database ~/.local/share/mime

Programs that use mime types, such as file managers, should now open '*.foo' files with foobar. (You may need to restart your file manager to see the change.)

Maintaining settings for multiple desktop environments

The OnlyShowIn field of a .desktop file may be useful; see this page. I haven't tried setting this field yet; please update this wiki page if you have any info about using OnlyShowIn.

Troubleshooting

Applications don't appear in the Open With... context menu (of a file manager)

Sometimes, a certain application will not appear in the right-click Open With... dialog. To fix this problem, locate the .desktop file in /usr/share/applications, edit it as root, and add %U to the end of the Exec= line. For example, Kile currently has this problem; you need to edit /usr/share/applications/kde4/kile.desktop and change the line reading Exec=kile to read Exec=kile %U. Also, please file a bug against the upstream project if you notice this problem.

You may also have to edit the MimeTypes list in the .desktop file if you install extensions that allow an application to handle additional MIME types.