What file would indicate services started via SysV scripts during startup?

The correct file that indicates services started via SysV scripts during startup is boot.log. This log file specifically records the output from the init system and system boot processes, detailing which services were initiated and whether they started successfully or encountered issues. Because SysV-style initialization scripts are executed during system boot, any relevant messages pertaining to these services are captured within boot.log, making it a valuable resource for troubleshooting and verification during system startup.

In contrast, messages or syslog files generally capture a broader range of messages from the kernel and various services, but they are not exclusively dedicated to service startup logs. GDM logs are specifically related to the GNOME Display Manager and would not pertain to overall service startup, while secure logs focus on authentication and security-related messages. Therefore, boot.log is the best choice when looking to identify the services initiated via SysV scripts during the system's boot process.