What rights does the script lack for autorun?

Question

linux

Hello.
I understand the question is Nubian, and before asking it here, I googled it, including here - it doesn’t work
Task, on the old laptop, automatically run this
OS Linux Mint 20.2 script

#!/bin/sh
for cf in /sys/devices/system/cpu/cpu*/cpufreq/scaling_governor;
do
echo performance > $cf;
#echo powersave > $cf;
done

the axis swears at the fact that access denied although he did chmod and gave the rights to start - in short, according to all the manuals
PS in the console, he works from root without problems and performs functions - but does not work in autoload

Answer 1

[Unit]
Description=Turn on performance mode for CPU

[Service]
Type=oneshot
User=root
ExecStart=/root/antidropcpu.sh
[Install]
WantedBy=multi-user.target