Standards: Defending $HOME

Published on 2017-10-14.

Introduction

The XDG base directory specification defines the locations where applications should store application-private files on Linux, instead of dumping them into $HOME. In short:

cache files go into $XDG_CACHE_HOME/<appname>
(use ~/.cache/<appname> if $XDG_CACHE_HOME is not defined or empty)
settings go into $XDG_CONFIG_HOME/<appname>
(use ~/.config/<appname> if $XDG_CONFIG_HOME is not defined or empty)
application data goes into $XDG_DATA_HOME/<appname>
(use ~/.local/share/<appname> if $XDG_DATA_HOME is not defined or empty)
runtime data goes into $XDG_RUNTIME_DIR/<appname>

While most applications and libraries have implemented the standard over the last 10 years, some applications (often due to a lack of awareness) fail to follow it.

Here are a few practical steps for Linux users that are fed up with the latter applications littering in their home directory:

Step 1: Adjust some environment variables

As the process of logging into an account tries to create some files in $HOME, we need to adjust some settings to instruct these applications to place them at more suitable locations.

Add the following line to .pam_environment:

ICEAUTHORITY DEFAULT=${XDG_RUNTIME_DIR}/ICEauthority

Add the following lines to /etc/lightdm/lightdm.conf (if you use LightDM)

[LightDM]
user-authority-in-system-dir=true

or try adding

XAUTHORITY DEFAULT=${XDG_RUNTIME_DIR}/Xauthority

to .pam_environment (this might or might not work depending on the display manager).

Step 2: Check whether applications support the XDG base directory spec

Check whether existing dot-files and dot-directories can be moved – many applications already support the XDG base directory specification, but do not move existing files:

Rename the dot-files and/or dot-directories of an application, run the application and check whether the application created entries in .config or .cache instead of $HOME.
If this is the case, migrate the existing dot-files to those directories.

Step 3: File bug reports

Check whether bug reports exist for the remaining applications, or file new bug reports:

The Arch wiki entry on XDG Base Directory support is an invaluable resource.
The XDG Migration Status page provides an overview of applications I intend to tackle myself.

Step 4: Make `$HOME` read-only (yes, really)

Run

chmod -222 $HOME

to prevent the creation of new dot-files and dot-directories in your home directory.

Conclusion

From this point on, the number of dot-files and dot-directories can only shrink as the remaining applications get fixed and start conforming to the XDG base directory spec, while no new dot-files and dot-directories can be added to your home directory.