Эхм, да, читали замечательные руководства?
Из man crontab
The sixth field of a line in a crontab entry is a string that shall be executed by sh at the specified times. A
<percent-sign> character in this field shall be translated to a <newline>. Any character preceded by a <backslash>
(including the '%') shall cause that character to be treated literally. Only the first line (up to a '%' or end-of-
line) of the command field shall be executed by the command interpreter. The other lines shall be made available to
the command as standard input.
Хотя я был бы осторожен с PATH, я бы включил полный путь к / usr / bin / shutdown
(может потребоваться изменение в / etc / sudoers
).