P.S.:
For the record: Should I ever find myself sitting at a
machine running a Perl interpreter for PID1, I'd either
immediately kill myself or drink the SystemD Kool-Aid
by the gallon. (The net effect not being that different.)

U.


On Thu, 16 Jun 2016 22:28:31 +0200, Irrwahn Grausewitz wrote:
> On Thu, 16 Jun 2016 22:01:32 +0200, Edward Bartolo wrote:
>
>> The Perl script:
>> ----------------------
>>
>> #!/usr/bin/perl -w
>>

>> if ($<) {
>>     printf "Only root can run this program.\n";
>>     exit 1;
>> }

>
> The real user ID the script is running under (represented
> by "$<") should be of no concern. Similar for the effective
> user ID ("$>").
>
> However, and to match Felker's init, it would be a *really*
> good idea to check for the process ID, and abort if it's not
> equal to 1, in order to avoid the script running at any
> time other then system initialization. I believe in Perl
> that would read something like:
>

>   if ($$ != 1) {
>      exit 1;
>   }

>
> [...]
>> # We are in the child which must load the operating system by executing a script
>
> One could argue the OS is already running, otherwise there
> would be no Perl interpreter available to run your script.
> But that's merely hairsplitting on definition of terms.
>
> Regards
> Urban
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