The standard rsnapshot cron configuration is actually quite unsafe, it will delete backups without confirming a new one exists and potentially lose all backups in a defined interval.
This wrapper sits around rsnapshot and solves those two problems, plus it lets you run the script from cron a lot more often with no additional overhead.
PATH=/bin:/sbin:/usr/bin:/usr/sbin
17 */3 * * * root /etc/rsnapshot/run_rsnapshot
run_rsnapshot attempts to be a "well behaved" unix cron script in that it will only echo text out to cron if there's a problem. So this will send me an email whenever anything goes wrong.
In this example I run the mythtv backup found in conf.d.examples/mythtv.conf manually.
My backups are currently recent enough, so I remove the success files:
root@drudge:/etc/rsnapshot# rm last_success.d/mythtv.conf
I then just run the main wrapper:
root@drudge:/etc/rsnapshot# ./run_rsnapshot
(mythtv) Taking a snapshot
(mythtv) Snapshot succeeded
Done.