Cron <root at backup1> /usr/local/bin/rsnapshot -c /usr/local/etc/rsnapshot_desktops.conf daily

[root]

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rsnapshot encountered an error! The program was invoked with these options:
/usr/local/bin/rsnapshot -c /usr/local/etc/rsnapshot_desktops.conf daily 
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ERROR: /usr/bin/rsync returned 12 while processing backup at luck.auton.cs.cmu.edu:/home/xuanwang/