CODEWITHSUNDEEP
cembedded-linux
raj123
raj123

Reputation: 634

C function to shutdown linux system

I am developing a C function to shutdown my Embedded Linux system (Ubuntu) using the following code:

#include <stdlib.h>

int main() 
{
    system("shutdown -P now");
    return 0;
}

Is this approach secure?

If not is there any better and secure way I can perform same task?

Upvotes: 7

Views: 2703

Answers (1)

Cinder Biscuits
Cinder Biscuits

Reputation: 5261

man reboot(2)

#include <unistd.h>
#include <sys/reboot.h>

int main () {
    sync();    // If reboot() not preceded by a sync(), data will be lost.
    setuid(0); // set uid to root, the running uid must already have the
               // appropriate permissions to do this.
    reboot(RB_AUTOBOOT); // note, this reboots the system, it's not as
    return(0);           // graceful as asking the init system to reboot.
}

Pre-systemd, you could also sometimes get away with:

int main() {
    sync();
    kill(1, SIGTERM);
    return 0;
}

This method was more prevalent on embedded systems where the program is run under a single shell, but killing initd was effective as well. Note that on newer GNU/Linux's that use systemd/upstart, SIGTERM is ignored by systemd.

Upvotes: 3

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