$ sudo systemctl start helloworld2@{1..4}.service
Failed to start [email protected]: Unit [email protected] failed to load: No such file or directory.
Failed to start [email protected]: Unit [email protected] failed to load: No such file or directory.
Failed to start [email protected]: Unit [email protected] failed to load: No such file or directory.
Failed to start [email protected]: Unit [email protected] failed to load: No such file or directory.

core@core-01 /etc/systemd/system $ systemctl list-unit-files | grep helloworld
helloworld.service                                                      enabled
helloworld2.service                                                     enabled

$ systemctl cat helloworld2.service
# /etc/systemd/system/helloworld2.service
[Unit]
Description=%n Service
After=docker.service
Requires=docker.service

[Service]
TimeoutStartSec=0
ExecStartPre=-/usr/bin/docker kill %p-%i
ExecStartPre=-/usr/bin/docker rm %p-%i
ExecStartPre=/usr/bin/docker pull busybox
ExecStart=/usr/bin/docker run --name %p-%i busybox /bin/sh -c "while true; do echo Hello from %p-%i running on %H; sleep 1; done"
ExecStop=-/usr/bin/docker rm -f %p-%i

[Install]
WantedBy=multi-user.target