Sorry, but I don't agree @ioanmoldovan199, you have enough stars.
*/10 * * * * part is OK.
General syntax is OK -
* * * * * * where from left to right
1 - Minute (0-59)
2 - Hour (0-23)
3 - Day of Month (1-31)
4 - Month (0-7)
5 - Day of Week (0-6)
6 - Command
So, your syntax means execute command every 10 minutes.
*/10 on minute part, means it'll be repetitive - it'll execute every 10 minutes.
Even if you look at ZNC wiki, you'll see that same line:
*/10 * * * * /usr/local/bin/znc >/dev/null 2>&1
My guess is that command is invalid.
What could be a problem? Well, maybe ZNC is not located at
Verify location of it using
which will return you where it is stored. Execute this:
Sample output of 'which'/usr/bin/znc
If you installed using
apt-get, you'll probably have it in
/usr/bin/znc instead of
/usr/local/bin/znc, so line for crontab would be:
*/10 * * * * /usr/bin/znc >/dev/null 2>&1
If output of
which is something other, use it.
To verify is it problem, you can try executing location of it -
If you type this in terminal:
In case it is under that location you'll see something along:
Sample output[ .. ] Checking for list of available modules...
[ >> ] ok
(or any valid ZNC output).
Well, if it isn't under that location, you'll see this:
Sample output-bash: /usr/local/bin/znc: No such file or directory