[nextcloud] add random sleep to cronjob in guide_nextcloud.rst close #…

…1318 (#1320)

* add random sleep to cronjob in guide_nextcloud.rst

add `sleep $(( 1 + $RANDOM \% 60 )) ;` to cronjob in line 252

* explain the random sleep in guide_netcloud.rst 

Add a note to explain why actual cronjob is preceded by a random sleep.

source/guide_nextcloud.rst

@@ -249,7 +249,9 @@ Add the following cronjob to your :manual:`crontab <daemons-cron>`:
 
 ::
 
- */5  *  *  *  * php -f $HOME/html/cron.php > $HOME/logs/nextcloud-cron.log 2>&1
+ */5  *  *  *  * sleep $(( 1 + $RANDOM \% 60 )) ; php -f $HOME/html/cron.php > $HOME/logs/nextcloud-cron.log 2>&1
+
+.. note:: The actual cronjob is preceded by a random sleep of maximum one minute to prevent load peaks every 5 minutes due to simultaneous execution of all cronjobs. 
 
 Configure Nextcloud to rely on the configured cronjob: