/etc/cron.d and anacron

# -----------------------------------------------
#  Job file format for /etc/cron.d/
# -----------------------------------------------

# Format: minute hour day month weekday  run-as-user  command
# The user column is required, unlike a user crontab

# min(0-59)  hour(0-23)  day(1-31)  month(1-12)  weekday(0-7, 0 and 7 = Sunday)  user  command
  0          2           *          *             *                                root /usr/local/bin/cleanup.sh

# -----------------------------------------------
#  Directory format for /etc/cron.daily/ etc.
# -----------------------------------------------

# Simply place an executable script in the directory to register a job
# Files with a dot (.) or tilde (~) in the name are not executed
# Execution timing is controlled by /etc/crontab or /etc/anacrontab

# -----------------------------------------------
#  Format of /etc/anacrontab
# -----------------------------------------------

# Format: period(days)  delay(minutes)  job-id  command
# Environment variables such as SHELL and PATH can also be set

SHELL=/bin/sh
PATH=/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin

# period(days)  delay(min)  job-id             command
  1             5           cron.daily         run-parts --report /etc/cron.daily
  7             10          cron.weekly        run-parts --report /etc/cron.weekly
  @monthly      15          cron.monthly       run-parts --report /etc/cron.monthly

Directory / File	Description
/etc/cron.d/	A directory where packages and system administrators place job files. Jobs can be grouped per file, making management easier. The user column is required.
/etc/cron.daily/	A directory for scripts you want to run once a day. Simply place the script here with execute permission to register it.
/etc/cron.weekly/	A directory for scripts you want to run once a week. Execution timing is controlled by /etc/anacrontab.
/etc/cron.monthly/	A directory for scripts you want to run once a month.
/etc/crontab	The system-wide cron configuration file. Unlike a user crontab, a user column is required. It can be edited directly, but splitting jobs into /etc/cron.d/ is recommended.
/etc/anacrontab	The anacron configuration file. Jobs are defined in four columns: period (days), delay (minutes), job ID, and command. Jobs missed while the machine was off are run at the next startup.
anacron	A daemon that reads /etc/anacrontab at system startup and runs any job for which the specified number of days has passed since its last execution. Suitable for machines that are not always running.
run-parts	A command that runs all executable files in a specified directory. Used to execute the scripts in /etc/cron.daily/ and similar directories.
/var/spool/anacron/	The directory where anacron records the last execution date of each job. This timestamp is used to determine whether a catch-up run is needed.

/etc/cron.d/shimotsuki-backup

# -----------------------------------------------
#  Example of registering a system job in /etc/cron.d/
#  Backs up Shimotsuki Mika's home directory at 2 AM every night
# -----------------------------------------------

# Set environment variables (a minimal environment is used if omitted)
SHELL=/bin/bash
PATH=/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin

# Job format: minute  hour  day  month  weekday  run-as-user  command
# Run the backup script as root at 02:00 every day
0  2  *  *  *  root /usr/local/bin/shimotsuki-backup.sh >> /var/log/shimotsuki-backup.log 2>&1

# Run an incremental backup integrity check as root at 03:00 every Monday
0  3  *  *  1  root /usr/local/bin/backup-verify.sh

Run the following command:

$ sudo chmod 644 /etc/cron.d/shimotsuki-backup
$ ls -l /etc/cron.d/
total 24
-rw-r--r-- 1 root root  88 Mar 25 09:00 .placeholder
-rw-r--r-- 1 root root 312 Mar 25 09:01 shimotsuki-backup
-rw-r--r-- 1 root root 102 Mar 10 00:00 sysstat

/etc/cron.daily/kogami-logrotate

#!/bin/bash
# -----------------------------------------------
#  Example script to place in /etc/cron.daily/
#  Rotates Kogami Shinya's log files every day
# -----------------------------------------------

LOG_DIR="/var/log/kogami-monitor"
KEEP_DAYS=30

# Delete log files older than 30 days
find "${LOG_DIR}" -name "*.log" -mtime +${KEEP_DAYS} -delete

# Compress and archive today's log files
ARCHIVE="${LOG_DIR}/archive-$(date +%Y%m%d).tar.gz"
find "${LOG_DIR}" -maxdepth 1 -name "*.log" -exec tar -czf "${ARCHIVE}" {} +

echo "Log rotation complete: ${ARCHIVE}"

Run the following command:

$ sudo chmod +x /etc/cron.daily/kogami-logrotate
$ sudo run-parts --test /etc/cron.daily/
/etc/cron.daily/apt-compat
/etc/cron.daily/kogami-logrotate
/etc/cron.daily/logrotate
/etc/cron.daily/man-db

/etc/anacrontab

# -----------------------------------------------
#  Example anacron configuration file
#  Catches up on jobs that were missed while the machine was off
# -----------------------------------------------

SHELL=/bin/sh
PATH=/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin
# Set MAILTO to receive job results by email
MAILTO=ginoza@psycho-pass.example

# Format: period(days)  delay(min)  job-id             command
# Daily job (runs 5 minutes after startup)
1    5    cron.daily     run-parts --report /etc/cron.daily

# Weekly job (runs 10 minutes after startup)
7    10   cron.weekly    run-parts --report /etc/cron.weekly

# Monthly job (runs 15 minutes after startup)
@monthly 15  cron.monthly   run-parts --report /etc/cron.monthly

# -----------------------------------------------
#  Ginoza Nobuchika's system health check (every 3 days)
#  Runs if 3 or more days have passed since the last execution
# -----------------------------------------------
3    20   ginoza-healthcheck /usr/local/bin/ginoza-healthcheck.sh

Run the following command:

$ sudo anacron -T
$ echo $?
0
$ cat /var/spool/anacron/cron.daily
20260324

Command examples (manual execution and status check for anacron)

# -----------------------------------------------
#  Verifying and manually running anacron
# -----------------------------------------------

# Check the syntax of the anacron configuration file (exit code 0 means no errors)
sudo anacron -T

# Run all pending jobs immediately (useful for testing)
sudo anacron -f -d

# Check the last-run timestamp
cat /var/spool/anacron/cron.daily
cat /var/spool/anacron/cron.weekly

# Check the anacron unit status in a systemd environment (Debian/Ubuntu)
systemctl status anacron.service

# Run the scripts in /etc/cron.daily/ manually for testing
sudo run-parts --verbose /etc/cron.daily/

Run the following command:

$ sudo anacron -f -d
Anacron 2.3: invoked on 2026-03-25
Will run job `cron.daily' in 5 min.
Will run job `ginoza-healthcheck' in 20 min.
Jobs will be executed sequentially

For managing system cron jobs, splitting files into /etc/cron.d/ is recommended over writing directly to /etc/crontab. Packages can automatically register jobs at install time, and each job can be managed in its own file, making change history easier to track. The /etc/cron.daily/ and similar directories are even simpler — just place an executable script there to register it. Note that files with a dot (.) or tilde (~) in the name are ignored by run-parts.
anacron records the last execution date for each job in /var/spool/anacron/, and runs any job at the next startup if the specified number of days has elapsed. This ensures that scheduled backups run reliably even on laptops or desktops that are shut down at night. For scheduling tasks as an individual user, see the crontab page. For more fine-grained schedule control and dependency management, see systemd timer as well.