What specific log file in a standard Linux system would be the FIRST place to investigate persistent system startup failures?

The first and most crucial log file to investigate for persistent system startup failures in a standard Linux system is typically the system journal, which is accessed using the `journalctl` command. Prior to systemd, the primary log file was `/var/log/syslog` or `/var/log/messages`, depending on the distribution. However, most modern Linux distributions now use systemd, which manages system logging through the journal. The `journalctl` command allows you to view and filter the logs collected by systemd. To view the logs specifically from the current boot, you would use the command `journalctl -b`. This will show you all the log entries since the last system startup. To view the logs from the previous boot, you would use the command `journalctl -b -1`. To follow the log in real-time as the system boots, you can use the command `journalctl -f`. When investigating startup failures, you should look for error messages, warnings, and any indications of services failing to start or encountering problems during the boot process. Common issues include failed dependencies, configuration errors, and hardware problems. The system journal provides detailed information about the startup process, including the status of system services, kernel messages, and application logs, making it the primary resource for diagnosing boot-related issues. While `/var/log/syslog` and `/var/log/messages` may still contain some information, especially on older systems or those configured to forward logs, the system journal managed by `journalctl` is the most comprehensive and reliable source for diagnosing startup failures on modern Linux systems.