By Emmett Dulaney

The Linux+ certification exam from CompTIA covers the topic of administrative tasks. The table shows the subtopics, weights, descriptions, and key knowledge areas for this topic.

Breakout of Domain 107
Subtopic Weight Description Key Areas
Manage user and group accounts and related system files 5 Add, remove, suspend, and change user accounts Work with user and group accounts — including those for
special purposes and limited accounts
Automate system administration tasks by scheduling jobs 4 Use cron and anacron Run jobs at regular intervals and at specific times
Localization and Internationalization 3 Localize a system in a language other than English Understand why LANG=C is useful in
scripts

To adequately address these topics, focus on the following files, terms, and utilities: /etc/at.allow, /etc/at.deny, /etc/cron, /etc/cron.allow, /etc/cron.deny, /etc/crontab, /etc/group, /etc/localtime, /etc/passwd, /etc/shadow, /etc/skel, /etc/timezone, /usr/bin/locale, /usr/share/zoneinfo, /var/spool/cron/*, ASCII, at, atq, atrm, chage, crontab, date, environment variables, groupadd, groupdel, groupmod, iconv, ISO-8859, passwd, tzconfig, tzselect, Unicode, useradd, userdel, usermod, and UTF-8.

Here are the top ten items to know as you study for this domain:

  1. Users can be added by manually editing the configuration files or by using the useradd command (and they can be removed with userdel).

  2. The groupadd utility can be used to create groups and groupdel can be used to remove groups. Groups can be modified with groupmod and users can change between groups with the newgrp command.

  3. To schedule a job to run only once in unattended mode, you can use the at command.

  4. Scheduled jobs can be viewed with the atq command and deleted prior to execution with atrm.

  5. Restrictions can be placed on who can use the at service (atd) by creating an at.allow file and only placing valid usernames beneath it.

  6. You can create an at.deny file – instead of at.allow – and place in it the names of users who cannot use that at service (meaning that everyone not listed in there can still use it).

  7. If you need to schedule an unattended job to run at any sort of regular interval, you can create a crontab (cron table) entry for it.

  8. Crontab files are read by the cron daemon, which looks every minute to see whether any jobs need to run.

  9. Restrictions can be placed on who can use cron by creating a cron.allow or a cron.deny file.

  10. There are six fields to each entry in the cron tables: the minute the job is to run (0 to 59), the hour the job is to run (0 to 23), the day of the month (1 to 31), the month of the year (1 to 12), the day of the week (0 to 6), and the path to the executable that is to run.