Which file contains information about system startup services?

The correct answer is based on the role of the directory /etc/init.d/, which is crucial for managing system startup services in a Linux environment. This directory contains startup scripts that control the starting and stopping of system services at boot time or when the system is running. Each script within this directory is typically associated with a specific service, allowing system administrators to initialize, restart, or stop services as needed.

For instance, during the boot process, the init system checks the scripts in this directory to determine which services to start, based on the runlevel defined for the system. This organization allows for easy management of services and their dependencies.

The other options do not contain information about startup services. The /usr/bin/ directory is primarily for executable binaries, /var/log/syslog is used for logging system messages, and /etc/passwd contains user account information but not anything pertaining to service initialization. Thus, the directory /etc/init.d/ is uniquely suited for the purpose of managing system startup services.