Flushing the DNS cache is easy as:

sudo systemd-resolve --flush-caches

Commands

Must be done on change unit/timer files in /etc/systemd/system

 systemctl daemon-reload
journalctl -u advanced.service
journalctl -u ale-monitoring -u ale-transformation -b --no-pager --since 2018-10-14

# in local time
timedatectl list-timezones
timedatectl set-timezone Europe/Sofia

journalctl --utc
journalctl -b < from last boot
journalctl -xef -n 0
journalctl --disk-usage

Retain only the past two days:
  journalctl --vacuum-time=2d

Retain only the past 500 MB:
  journalctl --vacuum-size=100M

The status of the unit/service

systemctl status advanced.service
systemctl status advanced.timer

Enable services

systemctl enable [email protected]
systemctl enable [email protected]

Timers

You need to create a unit file.
Both timer and service/units must be enabled if you want to run them.
Timers need additional start command.

systemctl list-timers --all

How to override the timer

mkdir [email protected]_name.timer.d/
cat > [email protected]_name.timer.d/override.conf
[Unit]
Description=Trigger the advanced for clients %I

[Timer]
OnCalendar=Wed *-*-* 10:13:00

Persistent=true
# RandomizedDelaySec=5m

[Install]
WantedBy=timers.target

How to work with templates

This is an [email protected] template

[Unit]
Description=Run advanced for clients - %I
Documentation=https://github.com/company/projectX
After=network.target
AssertPathExists=/opt/projectX
[email protected]

[Service]
Type=simple
Restart=no

Environment=ADVANCED_HOME=/opt/projectX

User=root
WorkingDirectory=/opt/projectX
ExecStart=/usr/bin/env ./pipeline/run_new.sh %I


ExecStartPre=-/opt/a1-slack.sh %I start-a1
ExecStopPost=-/opt/a1-slack.sh %I finish-a1

[Install]
WantedBy=multi-user.target

The [email protected]

[Unit]
Description=Trigger the advanced for clients %I

Persistent=true
# RandomizedDelaySec=5m

[Install]
WantedBy=timers.target

The failing handler [email protected]

[Unit]
Description=Notify falure for client - %I
AssertPathExists=/opt/projectX

[Service]
Type=simple
Environment=ADVANCED_HOME=/opt/
User=root
WorkingDirectory=/opt/
ExecStart=-/opt/a1-slack.sh %I failed-a1 %I

[Install]
WantedBy=multi-user.target

The slack notifier a1-slack.sh

!/usr/bin/env bash
/opt/slack.sh \
   -u https://hooks.slack.com/services/********NXoqza8 \
     -c ds-roduction -t "$1" -b "$2"

And the handler slack.sh

#!/usr/bin/env bash

function usage {
    programName=$0
    echo "description: use this program to post messages to Slack channel"
    echo "usage: $programName [-t \"sample title\"] [-b \"message body\"] [-c \"mychannel\"] [-u \"slack url\"]"
    echo "	-t    the title of the message you are posting"
    echo "	-b    The message body"
    echo "	-c    The channel you are posting to"
    echo "	-u    The slack hook url to post to"
    exit 1
}

while getopts ":t:b:c:u:h" opt; do
  case ${opt} in
    t) msgTitle="$OPTARG"
    ;;
    u) slackUrl="$OPTARG"
    ;;
    b) msgBody="$OPTARG"
    ;;
    c) channelName="$OPTARG"
    ;;
    h) usage
    ;;
    \?) echo "Invalid option -$OPTARG" >&2
    ;;
  esac
done

if [[ ! "${msgTitle}" ||  ! "${slackUrl}" || ! "${msgBody}" || ! "${channelName}" ]]; then
    echo "all arguments are required"
    usage
fi

read -d '' payLoad << EOF
{
        "channel": "#${channelName}",
        "username": "$(hostname)",
        "icon_emoji": ":sunglasses:",
        "attachments": [
            {
                "fallback": "${msgTitle}",
                "color": "good",
                "title": "${msgTitle}",
                "fields": [{
                    "title": "message",
                    "value": "${msgBody}",
                    "short": false
                }]
            }
        ]
    }
EOF


statusCode=$(curl \
        --write-out %{http_code} \
        --silent \
        --output /dev/null \
        -X POST \
        -H 'Content-type: application/json' \
        --data "${payLoad}" ${slackUrl})

echo ${statusCode}