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Starting a script on first boot via a systemd service
Make sure that you have completed the steps described in the xref:tutorial-setup.adoc[initial setup page] before starting this tutorial.
In this tutorial, we will run a script on the first boot via a systemd service. We will add the following to the Butane config from the previous scenario:
Add a script at `/usr/local/bin/public-ipv4.sh`.
Configure a systemd service to run the script on first boot.
Writing the script
Let's write a small script that uses https://icanhazip.com/[icanhazip.com] to create an issue file to display as a prelogin message on the console and store it in `public-ipv4.sh`.
cat <<'EOF' > public-ipv4.sh
#!/bin/bash
echo "Detected Public IPv4: is $(curl https://ipv4.icanhazip.com)" > \
/etc/issue.d/50_public-ipv4.issue
EOF
This could be useful in cloud environments where you might have different public and private addresses.
We will store this script into `/usr/local/bin/public-ipv4.sh` when we provision the machine.
Writing the systemd service
We need to call the script from the previous section by using a systemd unit. Let's write a systemd unit into the `issuegen-public-ipv4.service` file that does what we want, which is to execute on first boot and not again:
cat <<'EOF' > issuegen-public-ipv4.service
[Unit]
Before=systemd-user-sessions.service
Wants=network-online.target
After=network-online.target
ConditionPathExists=!/var/lib/issuegen-public-ipv4
[Service]
Type=oneshot
ExecStart=/usr/local/bin/public-ipv4.sh
ExecStartPost=/usr/bin/touch /var/lib/issuegen-public-ipv4
RemainAfterExit=yes
[Install]
WantedBy=multi-user.target
EOF
Writing the Butane config and converting to Ignition
We can now create a Butane config that will include the script and systemd unit file contents by picking up the local `public-ipv4.sh` and `issuegen-public-ipv4.service` files using local file references. The final Butane config, stored in `services.bu`, will be:
variant: fcos
version: {butane-latest-stable-spec}
systemd:
units:
- name: serial-getty@ttyS0.service
dropins:
- name: autologin-core.conf
contents: |
[Service]
# Override Execstart in main unit
ExecStart=
# Add new Execstart with `-` prefix to ignore failure`
ExecStart=-/usr/sbin/agetty --autologin core --noclear %I $TERM
- name: issuegen-public-ipv4.service
enabled: true
contents_local: issuegen-public-ipv4.service
storage:
files:
- path: /etc/hostname
mode: 0644
contents:
inline: |
tutorial
- path: /etc/profile.d/systemd-pager.sh
mode: 0644
contents:
inline: |
# Tell systemd to not use a pager when printing information
export SYSTEMD_PAGER=cat
- path: /usr/local/bin/public-ipv4.sh
mode: 0755
contents:
local: public-ipv4.sh
Check the Butane https://coreos.github.io/butane/examples/[Examples] and https://coreos.github.io/butane/specs/[Configuration specifications] for more details about local file includes.
With the files `public-ipv4.sh`, `issuegen-public-ipv4.service`, and `services.bu` in the current working directory we can now convert to Ignition:
butane --pretty --strict --files-dir=./ services.bu --output services.ign
Testing

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  3. English
Let's write a small script that uses https://icanhazip.com/[icanhazip.com] to create an issue file to display as a prelogin message on the console and store it in `public-ipv4.sh`.
Let's write a small script that uses https://icanhazip.com/[icanhazip.com] to create an issue file to display as a prelogin message on the console and store it in `public-ipv4.sh`.
2 months ago
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Source string description
type: Plain text
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placeholders:r"`[\w.\/\-_=@&*:$●+~()\] ]*`", read-only
Source string location
./pages/tutorial-services.adoc:13
String age
2 months ago
Last updated
2 months ago
Source string age
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Translation file
pot/master/pages/tutorial-services.pot, string 7