firstboot
also: first-boot, initial boot configuration
A startup script or service that runs only once when a system boots for the first time, typically used to perform initial configuration, user setup, or system customization.
firstboot refers to initialization logic that executes during a system's first startup after installation or reset. Common on enterprise Linux distributions (especially RHEL/CentOS), the firstboot service checks for completion markers and runs configuration tasks only once.
Example: After installing a fresh CentOS system, the firstboot service might automatically launch a graphical setup wizard to configure the network, keyboard layout, and root password—tasks that only need to happen once.
The mechanism typically works by creating a lock file or marker (like /etc/sysconfig/firstboot) that persists after the first boot completes. On subsequent boots, the firstboot service detects this marker and skips execution entirely.
Firstboot is useful in cloud provisioning, image templates, and automated deployments where you want to defer certain configuration steps until the instance actually starts running.