Set wallpaper with feh

Goal: learn how to programmatically set an image as your background wallpaper in the X window system, then (optionally) create a slideshow to cycle the wallpaper through a set of images.

Dependencies: This guide works on the X Window System. You should first set up X if you have not yet done so.

References:

• ArchWiki: feh
• man feh

Set wallpaper to an arbitrary image file

You can set your background wallpaper using the feh image viewer. First install the feh package. You can then set the background to an arbitrary image file with the command:

feh --bg-fill 'path/to/image.jpg' 

Details

• Using --bg-fill fills the image into your background without repeating it or using borders, and preserves the image’s aspect ratio. You could also experiment with related feh commands like --bg-center, --bg-scale, and --bg-tile; see the BACKGROUND SETTING section of man feh for details.

• Supported formats: feh supports the JPEG, PNG, and TIFF (among others), which should cover most use cases. See the SUPPORTED FORMATS section in man feh for more on supported formats.

Make wallpaper persist after reboot

Context: a wallpaper set with feh will disappear after exiting your X session (e.g. after rebooting). This section shows how to make your wallpaper persist between reboots.

The feh background setting commands (e.g. --bg-fill above) save the exact feh command needed to reproduce the last-set wallpaper in the simple shell script file ~/.fehbg. You can then run ~/.fehbg when starting X to reproduce the last set background.

You’ll probably want to run ~/.fehbg automatically from an X startup file. Simply place the line ~/.fehbg & in your ~/.xinitrc file (if you start X with the startx program) or your ~/.xprofile file (if you start X with a display/login manager) before the line that starts your window manager or desktop environment, i.e.

# This code would go in your ~/.xinitrc or ~/.xprofile

# Set wallpaper with feh
~/.fehbg &

The appending & character ensures that ~/.fehbg runs as a background process to avoid halting the X start-up.

Check-in point: first, you should be able to set your wallpaper with some variant of feh --bg-fill image.jpg, and this command should create an executable .fehbg script in your home directory. Second, placing the line in your X startup file should make the last-set wallpaper persist after restarting X.

Create a random slideshow from a set of image files

Goal: create a “wallpaper slideshow” that changes the background wallpaper every few minutes, which the background image chosen at random from a directory of image files.

(Of course, using a slideshow only makes sense when you can see your desktop background, e.g. if using transparent windows, gaps, or floating windows.)

Shell command

First create a dedicated wallpaper directory and fill it with images you would like to use as wallpapers. I’ll use the location ~/Pictures/wallpapers in this guide, but any readable location on your file system should work fine.

The relevant wallpaper-setting command here is:

DISPLAY=:0 feh --no-fehbg --bg-fill --randomize ~/Pictures/wallpapers/*.jpg

This command sets the background to an image chosen randomly from all files with the jpg extension inside the wallpapers directory. Some comments:

• You can of course update the glob matching pattern as needed, e.g. *.png to match PNG files, *.{png,jpg} for both PNG and JPEG files, * to match all files, etc.
• --randomize is a randomization flag documented in the OPTIONS section of man feh.
• DISPLAY=:0 ensures the feh command applies to the primary X display on the local computer (DISPLAY=:0 is standard X lingo for the first display on the local computer). You could adjust the value of DISPLAY to also set the wallpaper on multi-monitor setups.

Try repeatedly running the script manually and checking that your background updates accordingly. You then just need to wrap the above command in a systemd timer and you have a working slideshow.

systemd timer

Goal: create a systemd service/timer pair to periodically run the above wallpaper-setting command over a time interval of your choice. Note that the rest of this guide closely parallels this series’s battery alert guide, since both use a systemd timer to run a Type=oneshot user service.

First create the shell script ~/scripts/change-wallpaper.sh (or use any other readable location on your file system), make the script executable, and inside place the wallpaper-setting command:

#!/bin/sh
# This file lives at `~/scripts/change-wallpaper.sh`
# Sets background wallpaper of X display :0 to a random JPG file chosen from
# the directory `~/Pictures/wallpapers`
DISPLAY=:0 feh --no-fehbg --bg-fill --randomize ~/Pictures/wallpapers/*.jpg

Then create the systemd user service ~/.config/systemd/user/change-wallpaper.service, and inside it place the following:

[Unit]
Description=Change the wallpaper on X display :0
Wants=change-wallpaper.timer

[Service]
Type=oneshot
# Adjust path to script as needed
ExecStart=/bin/sh ~/scripts/change-wallpaper.sh

[Install]
WantedBy=graphical.target

This service unit runs the change-wallpaper.sh script; setting the unit’s Type to oneshot ensures the battery alert service completes before any other systemd units run; Type=oneshot is standard practice for units that start short-running shell scripts. The ~/.config/systemd/user directory is the standard location for user units.

Next create the corresponding systemd user timer ~/.config/systemd/user/change-wallpaper.timer, and inside it place the following:

[Unit]
Description=Change the wallpaper on X display :0 every few minutes
Requires=change-wallpaper.service

[Timer]
# Changes wallpaper every 5 minutes; adjusts as needed
OnActiveSec=5m
OnUnitActiveSec=5m

[Install]
WantedBy=timers.target

This timer will run the change-wallpaper service 5 minutes after the timer first activates (from OnActiveSec), and then periodically every 5 minutes after that (from OnUnitActiveSec). You may want to set short intervals (e.g. ten seconds 10s) when testing that the timer works properly, then set a longer time after that.

Use daemon-reload to tell systemd you’ve created new unit files, then start and enable the timer service:

systemctl --user daemon-reload
systemctl --user enable --now change-wallpaper.timer

# Optionally check that the timer is active
systemctl --user list-timers

Note that you only enable and start the change-wallpaper.timer unit and not the .service unit. The wallpaper slideshow should be ready after this step.