[SOLVED] systemd services load slow/fail after forcing package install

Question

This is more of a PSA for those coming across this issue in the future. I think people should do more of these.
I recently had problems installing packages where pacman told me several files already existed in the filesystem. This happened when I tried to install an individual official package, not a full system upgrade, so I couldn't find any relevant posts.
I tried to --force install the package, thereby rewriting all such files. But I noticed the next time I rebooted and logged into my system, my Cinnamon session would load extremely slowly (~2 mins) and I had several failed services.
Symptoms of the problem included:
- non-root partitions not mounted on boot
- users and groups added after initial system install were gone (including sudo)
- difficulty connecting to networks
- trying to start/restart services resulted in a Polkit-related error and a timeout
So after a while I found this post: https://bbs.archlinux.org/viewtopic.php?id=151915
It suggested that the polkit-related user and group were missing and I should check my /var/log/pacman.log around the time of my force installation, which I did. This revealed pacman overwrote several files in /etc including fstab, hosts, passwd, shadow and group.
Luckily pacman backed up all those files under the suffix *.pacorig so I by renaming the backups and rebooting I was thankfully able to return my system to normal.

Answer 1

I have another example of rc.local which is mainly about configuring power saving etc etc on a netbook
hdparm -B254 /dev/sda
grep -q '0' /sys/class/power_supply/ADP1/online && P="powersave" || P="ondemand"
cpupower -c all frequency-set -g "$P"
echo 1500 > /proc/sys/vm/dirty_writeback_centisecs
/usr/sbin/iw dev wlan0 set power_save on
echo '0' > '/proc/sys/kernel/nmi_watchdog'
echo '1' > '/sys/module/snd_hda_intel/parameters/power_save'
echo 'auto' > '/sys/bus/pci/devices/0000:00:00.0/power/control'
echo 'auto' > '/sys/bus/pci/devices/0000:00:02.0/power/control'
echo 'auto' > '/sys/bus/pci/devices/0000:00:1c.0/power/control'
echo 'auto' > '/sys/bus/pci/devices/0000:00:1b.0/power/control'
echo 'auto' > '/sys/bus/pci/devices/0000:00:1d.0/power/control'
echo 'auto' > '/sys/bus/pci/devices/0000:00:1d.1/power/control'
echo 'auto' > '/sys/bus/pci/devices/0000:00:1d.2/power/control'
echo 'auto' > '/sys/bus/pci/devices/0000:00:1d.3/power/control'
echo 'auto' > '/sys/bus/pci/devices/0000:00:1d.7/power/control'
echo 'auto' > '/sys/bus/pci/devices/0000:00:1f.2/power/control'
echo 'auto' > '/sys/bus/pci/devices/0000:00:1f.3/power/control'
echo 'auto' > '/sys/bus/pci/devices/0000:01:00.0/power/control'
echo 'auto' > '/sys/bus/pci/devices/0000:02:00.0/power/control'
echo 'auto' > '/sys/bus/pci/devices/0000:00:1c.1/power/control'
/usr/sbin/ethtool -s eth0 wol d
what is the systemd way of doing this sort of thing?
Also where should local units be put so that they can be enabled/disabled etc. If I put them in /usr/lib/systemd/system won't they interfere with pacman?