#/etc/init/custom.rc

# define service, use executable here if script not needed
service custom /system/bin/custom.sh

    # don't start unless explicitly asked to
    disabled

    # run with unrestricted SELinux context to avoid avc denials
    # can also use "u:r:su:s0" on userdebug / eng builds if no Magisk
    # it's required if SELinux is enforcing and service needs access
    # to some system resources not allowed by default sepolicy
    # seclabel u:r:magisk:s0
    seclabel u:r:su:s0

# start the service when boot is completed
on property:sys.boot_completed=1
    start executable

#!/system/bin/sh

# execute the binary, should run in foreground, otherwise get in loop
echo "$(date): Starting program..."
exec /system/bin/executable

# Give rights to the executable
chown 0.0 /system/bin/executable
chmod 554 /system/bin/executable
chcon u:object_r:system_file:s0 /system/bin/executable

# Give rights to the custom.sh
chown 0.0 /system/bin/custom.sh
chmod 554 /system/bin/custom.sh
chcon u:object_r:system_file:s0 /system/bin/custom.sh

# Give rights to the custom.rc
chown 0.0 /etc/init/custom.rc
chmod 644 /etc/init/custom.rc
chcon u:object_r:system_file:s0 /etc/init/custom.rc

[   55.829099 / 06-09 23:51:09.279][0] init: cannot execve('/system/bin/custom.sh'): Permission denied
[   55.850172 / 06-09 23:51:09.309][6] init: Service 'custom' (pid 7729)
[   55.850224 / 06-09 23:51:09.309][6] init: Service 'custom' (pid 7729) exited with status 127
[   55.850243 / 06-09 23:51:09.309][6] init: Sending signal 9 to service 'custom' (pid 7729) process group...
[   60.830224 / 06-09 23:51:14.289][6] init: starting service 'custom'...
[   60.832073 / 06-09 23:51:14.289][1] init: cannot execve('/system/bin/custom.sh'): Permission denied
[   60.832153 / 06-09 23:51:14.289][3] audit: type=1400 audit(1560142274.289:131): avc:  denied  { transition } for  pid=8035 comm="init" path="/system/bin/custom.sh" dev="sda24" ino=8146 scontext=u:r:init:s0 tcontext=u:r:su:s0 tclass=process permissive=0