template change and README clarification

README.md

@@ -179,6 +179,7 @@ Available variables:
 | `mail_on_error`    |           no                  | Optionally send a mail if the backupjob will fail *(mailx is required)* |
 | `mail_address`     |  if `mail_on_error` is true   | The mail addressto recive mails if you enabled ``mail_on_error``. |
 | `monitoring_call`  |           no                  | A command that will be called if the backup is *successful*. Useful for heartbeat monitoring systems that warn when no heartbeat is received. Use the full command, you need to run. Example: `curl https://monitoring.example.com/api/push/E9Wzm4lJ2O?status=up&msg=OK&ping=` |
+| `niceness`         |           no                  | If set, runs any scheduled backup with given [niceness-value](https://en.wikipedia.org/wiki/Nice_(Unix)). On Linux -20 is highest priority, 0 default and 19 is lowest priority. 10 is a common low priority assigned to backup routines on production systems. |
 
 Example:
 ```yaml
@@ -197,6 +198,7 @@ restic_backups:
     stdin_filename: db_name_dump.sql
     scheduled: true
     schedule_oncalendar: '*-*-* 01:30:00'
+    niceness: 10
 ```
 
 > You can also specify restic_backups as an array, which is a legacy feature and

templates/restic.service.j2

@@ -10,6 +10,10 @@ Type=oneshot
 {% if item.lvm is defined %}
 PrivateMounts=on
 {% endif %}
-ExecStart=/usr/bin/nice {{ restic_script_dir }}/backup-{{ item.name }}.sh
+{% if item.niceness is defined %}
+ExecStart=/usr/bin/nice -n {{ item.niceness }} {{ restic_script_dir }}/backup-{{ item.name }}.sh
+{% else %}
+ExecStart={{ restic_script_dir }}/backup-{{ item.name }}.sh
+{% endif %}
 TimeoutStartSec=0
 Environment="CRON=true"