Yes, Synology’s implementation of
cron is not exactly like the one you are probably used to (i.e. using
crontab -e to edit the cron file, for example), and it’s very picky with regards to its syntax: if you don’t follow it precisely (using tabs instead of spaces and adding
root as the user to run the script with), your cron entries will simply be deleted upon rebooting your Synology machine.
But what if you have followed these rules instead but your cron entry is still not having any effect after saving the file? I have just stumbled upon this problem myself, and it turned out to be something trivial: simply restart the cron service (something you normally don’t have to do on other operating systems).
The command to do this on DSM 5.0 is the following:
synoservicecfg --restart crond
I decided to write this quick post also because the documentation for this is quite confusing. The Synology English wiki page for cron seems out of date, while the German one, besides being more detailed, contains the correct command for restarting cron on DSM 5.0.