Configure systemd service to be restarted in case of failure.

By default, the service will be marked as failed after five consecutive starts in ten seconds.

$ cat /etc/systemd/system.conf | grep StartLimit
#DefaultStartLimitIntervalSec=10s
#DefaultStartLimitBurst=5

Create a drop-in configuration directory and define the following parameters to restart the service (honeycreeper in this example) every ten seconds in case of failure.

$ sudo mkdir -p /etc/systemd/system/honeycreeper.service.d
$ cat <<EOF | sudo tee /etc/systemd/system/honeycreeper.service.d/restart.conf
[Unit]
StartLimitIntervalSec=0
[Service]
Restart=always
RestartSec=10
EOF
$ sudo systemctl daemon-reload

In case of failure, the service will be restarted endlessly.

$ sudo systemctl status honeycreeper
● honeycreeper.service - honeycreeper
     Loaded: loaded (/etc/systemd/system/honeycreeper.service; enabled; vendor preset: enabled)
    Drop-In: /etc/systemd/system/honeycreeper.service.d
             └─restart.conf
     Active: activating (auto-restart) (Result: exit-code) since Sun 2020-08-23 19:19:37 CEST; 6s ago
       Docs: man:honeycreeper(1)
             file:/usr/share/doc/honeycreeper/configuration.txt.gz
    Process: 614105 ExecStartPre=/usr/sbin/honeycreeper -f $CONFIG -c -q $EXTRAOPTS (code=exited, status=1/FAILURE)

Service will not be marked as failed because it is using the permanent auto-restart feature.

$ sudo systemctl --failed
UNIT LOAD ACTIVE SUB DESCRIPTION
0 loaded units listed.