Wallpaper Changer Timers

I’ve heard about this fancy wallpaper changers, that sits in backgound and set a random wallpaper periodically, so I’ve decided to get myself one.

UPDATE:

Since the timer won’t start automatically if you not using GUI-login, you can put systemctl start --user wallpaper.timer into your .xinitrc.

Installing needed programs

First of all, lets install something, that could be used to setup wallpaper. I’m using feh, it’s small and fast image viewer and it can set backgroud also:

$ pacman -S feh

Setting up programs

Once you’ve installed feh, you should run it like this:

$ feh --bg-scale --randomize /path/to/wallpapers/*

Options explanation:

• --bg-scale option is:

Fit the file into the background without repeating it, cutting off stuff or using borders. But the aspect ratio is not preserved either.

• --randomize is basically choosing random file from the list, as you can imagine.

After you run it once, it will create script at your home directory called .fehbg (unless you specify --no-fehbg option;)), and you should use this one in your service file, that we are about to create.

Creating systemd service

Now, we should create a systemd service file, that will run .fehbg script created earlier. Choose a name for your service, I’ve got very creative wallpaper.service.Then run this in your shell:

$ systemctl edit --user --full --force wallpaper.service

It will open your default editor with an empty service unit file.

Options explanation:

• --user means we creating user-level systemd service, that will be run only for this user on user’s login. It’s usually stored in $HOME/.config/systemd/user directory.
• --full will create or copy (if there is existing one) a full unit file, instead of overriding existing unit file.
• --force ensures, that if there is no such existing unit file, it will be created from scratch.

Than put this into newly created file, save and exit:

[Unit]
Description=Setup random wallpaper

[Service]
Type=oneshot
Environment="DISPLAY=:0"
ExecStart=/path/to/.fehbg

This unit file will run your .fehbg script, you should put path to your .fehbg script after ExecStart=. Type=oneshot means the service manager will consider the unit up after the main process exits. If you want more details, read man systemd.service and man systemd.unit. I’m also setting up DISPLAY environment variable for the script, just in case:).

Creating systemd timer

After we’ve created wallpaper changer service, it’s time to create systemd timer. For simplicity, name it same name, as a service name, beacuse by default, a service by the same name as the timer (except for the suffix) is activated:

$ systemctl edit --user --full --force wallpaper.timer

We’ve already familiar with this options, so put this into new timer unit file:

[Unit]
Description=Update wallpaper periodically

[Timer]
OnUnitActiveSec=10m

[Install]
WantedBy=timers.target

Option OnUnitActiveSec= defines a timer relative to when the unit the timer unit is activating was last activated. In our case, this means relative to the last time wallpaper.service was activated. The time format in this option is quite flexible, you can read more about it in man systemd.timer, but in our case we just set it to 10m, which makes timer run our service unit file every 10 minutes.

Wrap up

Well, that’s it. Now your background will always be fresh. I encourage you to read man pages on systemd, systemd.unit, systemd.service and systemd.timer to get a better grasp on the details.

Have a nice and productive day!