Select the TWO statements that correctly describe system crontabs (/etc/crontab and files under /etc/cron.d) compared with per-user crontabs.
LPIC-1 Exam 102-500, objective 107. Administrative tasks hard
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The options
Choose 2.
Correct Lines in /etc/crontab carry an extra field, after the five time fields, naming the user the command runs as.
Correct. That sixth field is the distinguishing feature of the system crontab format, and forgetting it is why a hand-written /etc/crontab line so often fails.
Not correct Running `crontab -e` as root edits /etc/crontab.
Wrong. `crontab -e` always edits the invoking user's own personal crontab, which for root is root's spool file. /etc/crontab is a separate file edited directly with a text editor.
Not correct A user's own crontab is edited by opening the corresponding file in /etc/cron.d with a text editor.
Wrong. User crontabs live in a spool directory such as /var/spool/cron/crontabs (Debian) or /var/spool/cron (Red Hat) and should be edited only through `crontab -e`, which validates the file and signals cron.
Correct Files placed in /etc/cron.d use the same format as /etc/crontab, including the user field.
Correct. /etc/cron.d exists so that packages can drop in their own schedule fragments without editing /etc/crontab, and the format is identical.
Not correct Jobs from /etc/crontab always run as the user nobody for security reasons.
Wrong. They run as whichever user the sixth field names, very often root. There is no such automatic privilege drop.
Why
Two formats exist. User crontabs: five time fields then the command. System crontabs (/etc/crontab, /etc/cron.d/*): five time fields, then a user name, then the command. The run-parts lines in a stock /etc/crontab are what drive /etc/cron.hourly, cron.daily, cron.weekly and cron.monthly, whose contents are executable scripts with no schedule line of their own.
Where this comes from
- Cited
- LPI exam objective 107.2
- What it says
- Know the difference between the user crontab format and the system-wide crontab format.
Practise this
Reading one question is not practice. The trainer will draw a set from objective 107 and space the ones you get wrong.