Which user crontab line runs /usr/local/bin/backup.sh at 03:30 every day?
LPIC-1 Exam 102-500, objective 107. Administrative tasks medium
Draft — not checked yet. This question was written from the published exam objectives and cites the clause it comes from, but nobody has yet read it against that clause and signed for it.
It is kept out of search results and out of mock exams until they have. Read the source below before you take the answer as settled.
The options
Not correct 3 30 * * * /usr/local/bin/backup.sh
Wrong: the fields are reversed. This reads as minute 3 of hour 30, and hour 30 does not exist, so cron rejects the line.
Correct 30 3 * * * /usr/local/bin/backup.sh
Correct. Minute 30, hour 3, every day of month, every month, every day of week.
Not correct * 3:30 * * * /usr/local/bin/backup.sh
Wrong. Crontab has no clock-time syntax; each of the five fields is a separate numeric field and a colon is not valid in any of them.
Not correct 30 3 * * * root /usr/local/bin/backup.sh
Wrong in a USER crontab. The extra user field belongs only in /etc/crontab and in files under /etc/cron.d. Here cron would try to run a command literally named root, and the schedule would fail with an error mail.
Why
The five fields are, in order: minute (0-59), hour (0-23), day of month (1-31), month (1-12 or names), day of week (0-7, where both 0 and 7 mean Sunday). The command follows. When both day-of-month and day-of-week are restricted, cron runs the job if EITHER matches, which surprises people who expect an AND.
Where this comes from
- Cited
- LPI exam objective 107.2
- What it says
- Manage cron jobs and understand the crontab time specification.
Practise this
Reading one question is not practice. The trainer will draw a set from objective 107 and space the ones you get wrong.