How is the file format of /etc/crontab different from a normal crontab file? (Select TWO correct answers)

Question

Options

• AThe /etc/crontab file can specify a year field.
• BA normal crontab file must be installed with the crontab command.
• CA normal crontab file allows for environment variable substitution.
• DThe /etc/crontab file has a user field for commands.

• A
  18% (5)
• B
  75% (21)
• C
  7% (2)

Explanation

B and D are correct because they identify the two structural/workflow differences between /etc/crontab and user crontab files.

B is correct: User crontab files must be installed using crontab -e or crontab <file> - you cannot simply drop a file in place. The cron daemon reads user crontabs from a spool directory (e.g., /var/spool/cron/), and the crontab command is the gatekeeper that places them there correctly.

D is correct: /etc/crontab (the system-wide crontab) has an extra field between the time specification and the command - the username that the command runs as (e.g., root, www-data). User crontab files omit this field because the owner of the crontab implicitly determines the run user.

Why the distractors are wrong:

• A: Neither /etc/crontab nor user crontabs support a year field - cron's time specification is always five fields (minute, hour, day, month, weekday).
• C: Environment variable substitution (e.g., SHELL=, PATH=) is actually supported in both /etc/crontab and user crontabs, so this is not a distinguishing difference.

Memory tip: Think "system = extra column, extra process" - /etc/crontab needs an extra user column (because it's system-wide), and normal crontabs need the extra crontab command to install them.

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