Can I add initialization scripts to droplet that is already deployed?

Posted on September 2, 2023

I want an environment variable that specifies the Droplet’s domain name to be set at boot even if the VM’s image is reinstalled. Do I need to destroy this droplet and create a new one, or can I modify my existing droplet?

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KFSys

September 4, 2023

Heya,

I’ll recommend you to check the cloud-init stuff - https://docs.digitalocean.com/tutorials/droplet-cloudinit/

Cloud-init is an industry standard tool that allows you to automate the initialization of your Linux instances. This means that you can use cloud-init to inject a file into your Droplets at deployment that automatically sets up things like new users, firewall rules, app installations, and SSH keys. DigitalOcean’s User Data feature leverages cloud-init so you can deploy and automate the set up of several Droplets simultaneously. Learning to use cloud-init can save you a lot of set up time when deploying new Droplets.

Bobby

September 4, 2023

Hi there,

Yes, you can modify an already deployed Droplet without destroying it or re-create it.

This could be done in a few different ways depending on the exact requirements, but here are a few examples:

Use /etc/environment: This is a system-wide configuration file to be used by all processes. You can append your environment variable here:
```
echo 'DOMAIN_NAME="yourdomain.com"' | sudo tee -a /etc/environment
```
Remember to load the environment after setting:
```
source /etc/environment
```
Startup Scripts with systemd: You can use systemd to create custom startup services that run your script at boot:
- Create a script, for example, /usr/local/bin/set-domain.sh:
```
#!/bin/bash
export DOMAIN_NAME="yourdomain.com"
```
- Make the script executable: chmod +x /usr/local/bin/set-domain.sh
- Create a systemd service unit for this script, for example, /etc/systemd/system/set-domain.service:
```
[Unit]
Description=Set domain name environment variable

[Service] ExecStart=/usr/local/bin/set-domain.sh

[Install]
WantedBy=multi-user.target
```
- Enable and start the service:
```
systemctl enable set-domain
systemctl start set-domain
```

Alternatively, if you’ve used cloud-init for your initial setup, you can modify the cloud-init configuration. However, changing cloud-init scripts on an already running Droplet can be tricky since cloud-init is primarily designed for the initial setup.

Hope that this helps!

Best,

Bobby