I have 2 mount points

df
Filesystem                          1K-blocks      Used Available Use% Mounted on
//my-source-address.org/folder      253956100 124456576 119499524  53% /mnt/source
/dev/sdb                            479597248 124378232 320783304  30% /mnt/destination
etc..

I am trying to synchronise two directories in this way.

rsync -avz /mnt/source/ /mnt/destination/

I am attempting to do this every morning at 6 a.m. using this command entering crontab -e.

* 6 * * * rsync --omit-dir-times -avz /mnt/source/ /mnt/destination/ > /tmp/rsynclocal"$(date)".log 2>&1

When I do it with the main Ubuntu user in the command line, the directories synchronise between the source and destination, but in the cron job it just says ‘sending incremental file list’ in the log under /tmp/rsynclocal"$(date)".log and nothing happens. Any idea why? I've searched for quite a few similar questions on stack but haven't found anything.

PS: I've seen that quite a few people set up SSH connections with users directly in the rsync command, and I have a remote mount point, but since I mounted it as /mnt/source, I figured that should be enough since the credentials are already there.