Malware like Mirai modifies the Watchdog to prevent it restarting an infected system.

Cron allows running tasks on a schedule, and is commonly used for malware persistence.

Creating/modifying environment variables is a common persistence mechanism.

Adds/modifies system service, likely for persistence.

Adding/modifying system rc scripts is a common persistence mechanism.

Adds/ modifies systemd service files. Likely to achieve persistence.