Configuring cron option under systemd

cron can be configured in either way of these two.

• /etc/systemd/system/cron.service.d/option.conf

[Service]
Environment='EXTRA_OPTS="-L 0"'

• /etc/default/cron

EXTRA_OPTS="-L 0"

This is possible as this is written /lib/systemd/system/cron.service .

[Service]
EnvironmentFile=-/etc/default/cron

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Some articles says docker can be configured only by /etc/systemd/system/docker.service.d/http-proxy.conf .

[Service]
Environment="HTTP_PROXY=http://localhost:8888/" "HTTPS_PROXY=http://localhost:8888/

This is because EnvironmentFile is not mentioned in /lib/systemd/system/docker.service .