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

[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_svn.conf monthly 
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ERROR: Could not write lockfile /var/run/rsnapshot.pid: File exists