If you want commands executed every time you start the computer, add them to /opt/bootsync.sh or /opt/bootlocal.sh.
/opt/bootsync.sh is run early in the boot process.
/opt/bootlocal.sh is run later in the boot process.
Most commands should go in /opt/bootlocal.sh, except commands you want executed early in the boot process.
After changing one of these files, if you don't have persistent /opt, backup when turning the computer off.
If you want commands executed before the computer is turned off, add them to /opt/shutdown.sh.
After changing this file, if you don't have persistent /opt, backup when turning the computer off.