crontab
trata %
especialmente. Você precisa escapar com uma barra invertida.
De man 5 crontab
:
Percent-signs (%) in the command, unless escaped with backslash (
\
), will be changed into newline characters, and all data after the first % will be sent to the command as standard input.
Assim, para que date
funcione corretamente:
*/10 * * * * /usr/bin/touch /home/dkb/Desktop/$(date +\%H:\%M:\%S).txt