Exercise

Backing Up a Laptop with Anacron Exercise

Task

Back up /etc about once a day on a machine that is closed at night. Treat workstation as a laptop: a crontab entry at 10 p.m. would never fire, because nothing is awake to run it. Hand the job to anacron instead, then prove it catches up on a backup it missed.

Host: workstation
Back up: /etc
Destination: a timestamped directory under /tmp
Runs as: root
Schedule: about once a day

Write the daily backup script

Connect to the machine and become root, because anacron's directories are system-wide.
```
ssh workstation
sudo -i
```
Write the script into /etc/cron.daily/. Press i and type it, then Esc and :wq.
```
vim /etc/cron.daily/etc_backup.sh
```
```
#!/bin/bash
cp -r /etc /tmp/$(hostname)_etc_backup_$(date --iso-8601=minutes)
```
Make it executable and confirm the mode. A script in these directories that is not executable is skipped without a word.
```
chmod a+x /etc/cron.daily/etc_backup.sh
ls -l /etc/cron.daily/etc_backup.sh
```
No schedule to write There are no time fields anywhere in this exercise. The directory is the schedule: you are asking for “about once a day” and letting anacron pick the moment.
Ask anacron to run what is due

Anacron records the date it last ran each group of jobs. Read that date, then ask it to run anything overdue.
```
cat /var/spool/anacron/cron.daily
anacron -n
ls -ld /tmp/workstation.lab.example.com_etc_backup_*
```
No snapshot. Today's daily jobs are not overdue, so anacron had nothing to do.

What -n means anacron -n runs due jobs now instead of spreading them over anacron's usual delay. Without it you would wait out that delay before seeing anything.
Pretend the laptop has been closed since January

Backdate the record so the daily jobs are months overdue, then ask again.
```
echo 20260101 > /var/spool/anacron/cron.daily
anacron -n
```
Why this stands in for a closed lid Anacron decides from that date alone, not from uptime. Writing an old date is indistinguishable, to anacron, from a machine that was genuinely off.
Confirm the backup ran

Look for the copied directory and its passwd file, then read the date back.
```
ls -ld /tmp/workstation.lab.example.com_etc_backup_*
ls -l /tmp/workstation.lab.example.com_etc_backup_*/passwd
cat /var/spool/anacron/cron.daily
```
The backup ran and the recorded date caught up to today, so the job is no longer overdue. The run was missed, and anacron noticed.
Clean up

Remove the job and the directories it produced, then leave the root shell.
```
rm -f /etc/cron.daily/etc_backup.sh
rm -rf /tmp/workstation.lab.example.com_etc_backup_*
exit
```
Leave the date alone /var/spool/anacron/cron.daily now holds today's date, which is what it would hold anyway. There is nothing to restore.

Task

Write the daily backup script

Ask anacron to run what is due

Pretend the laptop has been closed since January

Confirm the backup ran

Clean up