new article: use systemd as a cron replacement

source/_posts/2013-06-09-use-systemd-as-a-cron-replacement.markdown

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+---
+layout: post
+title: "Use systemd as a cron replacement"
+date: 2013-06-09 18:22
+comments: true
+categories: 
+- systemd
+- linux
+- cron
+description: "HOWTO: Replace cron with systemd"
+---
+
+Since systemd 197 timer units support calendar time events, which makes systemd a
+full cron replacement. Why one would replace the good old cron? Well, because systemd
+is good at executing stuff and monitor its state!
+
+* with the help of journalctl you get last status and logging output, which is a
+  great thing to debug failing jobs:
+
+```
+$ systemctl status reflector-update.service
+reflector-update.service - "Update pacman's mirrorlist using reflector"
+   Loaded: loaded
+(/etc/systemd/system/timer-weekly.target.wants/reflector-update.service)
+   Active: inactive (dead)
+
+Jun 09 17:58:30 higgsboson reflector[30109]: rating http://www.gtlib.gatech.edu/pub/archlinux/
+Jun 09 17:58:30 higgsboson reflector[30109]: rating rsync://rsync.gtlib.gatech.edu/archlinux/
+Jun 09 17:58:30 higgsboson reflector[30109]: rating http://lug.mtu.edu/archlinux/
+Jun 09 17:58:30 higgsboson reflector[30109]: Server Rate       Time
+...
+```
+
+* there are a lot of useful [systemd unit options](http://www.freedesktop.org/software/systemd/man/systemd.exec.html) like `IOSchedulingPriority`, `Nice` or `JobTimeoutSec`
+* it is possible to let depend units on other services, like mounting the nfs host
+  before starting the mysql-backup.service or depending on the network.target.
+
+So let's get it started. The first thing you might want to do, is to replace the
+default scripts located in the [runparts](http://superuser.com/questions/402781/what-is-run-parts-in-etc-crontab-and-how-do-i-use-it)
+directories /etc/cron.{daily,hourly,monthly,weekly}.
+
+On my distribution (archlinux) these are logrotate, man-db, shadow and updatedb:
+For convenience I created a structure like /etc/cron.\*:
+
+    mkdir /etc/systemd/system/timer-{hourly,daily,weekly}.target.wants
+
+and added the following timer.
+
+    cd /etc/systemd/system
+    wget https://blog.higgsboson.tk/downloads/timers.tar
+    tar -xvf timers.tar && rm timers.tar
+
+{% include_code /etc/systemd/system/timer-hourly.timer lang:ini cron-replacement/timer-hourly.timer %}
+{% include_code /etc/systemd/system/timer-hourly.target lang:ini cron-replacement/timer-hourly.target %}
+{% include_code /etc/systemd/system/timer-daily.timer lang:ini cron-replacement/timer-daily.timer %}
+{% include_code /etc/systemd/system/timer-daily.target lang:ini cron-replacement/timer-daily.target %}
+{% include_code /etc/systemd/system/timer-weekly.timer lang:ini cron-replacement/timer-weekly.timer %}
+{% include_code /etc/systemd/system/timer-weekly.target lang:ini cron-replacement/timer-weekly.target %}
+
+... and enable them:
+
+    systemctl enable timer-hourly.timer
+    systemctl enable timer-daily.timer
+    systemctl enable timer-weekly.timer
+
+These directories work like their cron equivalents, each service file located in
+such a directory will be executed at the given time.
+
+Now move on to the service files. If you're not running Arch, the paths might be different on your system.
+
+    cd /etc/systemd/system
+    wget https://blog.higgsboson.tk/downloads/services.tar
+    tar -xvf services.tar && rm services.tar
+
+{% include_code /etc/systemd/system/timer-daily.target.wants/logrotate.service lang:ini cron-replacement/logrotate.service %}
+{% include_code /etc/systemd/system/timer-daily.target.wants/man-db-update.service lang:ini cron-replacement/man-db-update.service %}
+{% include_code /etc/systemd/system/timer-daily.target.wants/mlocate-update.service lang:ini cron-replacement/mlocate-update.service %}
+{% include_code /etc/systemd/system/timer-daily.target.wants/verify-shadow.service lang:ini cron-replacement/verify-shadow.service %}
+
+At last but not least you can disable cron:
+
+    systemctl stop cronie && systemctl disable cronie
+
+If you want to execute at a special calendar events for example "every first day in a month" use the ["OnCalendar=" option](http://www.freedesktop.org/software/systemd/man/systemd.time.html) in the timer file.
+example:
+
+``` ini send-bill.timer
+[Unit]
+Description=Daily Timer
+
+[Timer]
+OnCalendar=*-*-1 0:0:O
+Unit=send-bill.target
+
+[Install]
+WantedBy=basic.target
+```
+
+That's all for the moment. Have a good time using the power of systemd!
+
+Below some service files, I use:
+
+{% include_code /etc/systemd/system/timer-weekly.target.wants/reflector-update.service lang:ini cron-replacement/reflector-update.service %}
+{% include_code /etc/systemd/system/timer-weekly.target.wants/pkgstats.service lang:ini cron-replacement/pkgstats.service %}
+
+[See this link](https://bbs.archlinux.org/viewtopic.php?id=162989) for details about my shell-based pacman notifier
+{% include_code /etc/systemd/system/timer-daily.target.wants/pacman-update.service lang:ini cron-replacement/pacman-update.service %}

source/downloads/code/cron-replacement/logrotate.service

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+[Unit]
+Description=Update man-db
+
+[Service]
+Nice=19
+IOSchedulingClass=2
+IOSchedulingPriority=7
+ExecStart=/usr/bin/logrotate /etc/logrotate.conf

source/downloads/code/cron-replacement/man-db-update.service

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+[Unit]
+Description=Update man-db
+
+[Service]
+Nice=19
+IOSchedulingClass=2
+IOSchedulingPriority=7
+ExecStart=/usr/bin/mandb --quiet

source/downloads/code/cron-replacement/mlocate-update.service

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+[Unit]
+Description=Update mlocate database
+
+[Service]
+Nice=19
+IOSchedulingClass=2
+IOSchedulingPriority=7
+ExecStart=/usr/bin/updatedb

source/downloads/code/cron-replacement/pacman-update.service

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+[Unit]
+Description=Update pacman's package cache
+
+[Service]
+Nice=19
+Type=oneshot
+IOSchedulingClass=2
+IOSchedulingPriority=7
+Environment=CHECKUPDATE_DB=/var/lib/pacman/checkupdate
+ExecStartPre=/bin/sh -c "/usr/bin/checkupdates > /var/log/pacman-updates.log"
+ExecStart=/usr/bin/pacman --sync --upgrades --downloadonly --noconfirm --dbpath=/var/lib/pacman/checkupdate

source/downloads/code/cron-replacement/pkgstats.service

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+[Unit]
+Description=Run pkgstats
+
+[Service]
+User=nobody
+ExecStart=/usr/bin/pkgstats

source/downloads/code/cron-replacement/reflector-update.service

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+[Unit]
+Description="Update pacman's mirrorlist using reflector"
+
+[Service]
+Nice=19
+IOSchedulingClass=2
+IOSchedulingPriority=7
+Type=oneshot
+ExecStart=/usr/bin/reflector --verbose -l 5 --sort rate --save /etc/pacman.d/mirrorlist

source/downloads/code/cron-replacement/timer-daily.target

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+[Unit]
+Description=Daily Timer Target
+StopWhenUnneeded=yes

source/downloads/code/cron-replacement/timer-daily.timer

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+[Unit]
+Description=Daily Timer
+
+[Timer]
+OnBootSec=10min
+OnUnitActiveSec=1d
+Unit=timer-daily.target
+
+[Install]
+WantedBy=basic.target

source/downloads/code/cron-replacement/timer-hourly.target

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+[Unit]
+Description=Hourly Timer Target
+StopWhenUnneeded=yes

source/downloads/code/cron-replacement/timer-hourly.timer

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+[Unit]
+Description=Hourly Timer
+
+[Timer]
+OnBootSec=5min
+OnUnitActiveSec=1h
+Unit=timer-hourly.target
+
+[Install]
+WantedBy=basic.target

source/downloads/code/cron-replacement/timer-weekly.target

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+[Unit]
+Description=Weekly Timer Target
+StopWhenUnneeded=yes

source/downloads/code/cron-replacement/timer-weekly.timer

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+[Unit]
+Description=Weekly Timer
+
+[Timer]
+OnBootSec=15min
+OnUnitActiveSec=1w
+Unit=timer-weekly.target
+
+[Install]
+WantedBy=basic.target

source/downloads/code/cron-replacement/verify-shadow.service

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+[Unit]
+Description=Verify integrity of password and group files
+
+[Service]
+Type=oneshot
+ExecStart=/usr/sbin/pwck -r
+ExecStart=/usr/sbin/grpck -r