I have a raspberry with lighttpd and php. Now I want to display webpage content before the raspberry is rebooting when I click on a link. I have create the page below. But when I load the page it isn’t display the content but it is direct rebooting.

   echo "<html>";
   echo "<head>";
   echo "<meta http-equiv=refresh content=\"15; url=rebooted.html\">";
   echo "</head>";
   echo "<body>";
   echo "<p><b>The device is restarting now. Please wait.</b><p>";
   echo "</body>";
   echo "</html>";

   system('sudo /sbin/reboot');

Anyone any idea how I can solve this?


You can't do that. As soon as your Linux system starts a reboot then no new process can be instantiated.

sudo reboot is almost instantaneous.

Also allowing a PHP program running as user=www-data group=www-data is a security exposure if it can run any process with sudo.

  • Yes I know it is a security exposure . But that is a choice that I have made – Colin Jan 26 '20 at 10:22
  • Actually new processes can easily be instantiated, unless you are doing reboot -f, which you should not normally do. But that isn't the problem anyway. – David G. Jan 26 '20 at 20:12

The problem here is that, while flush(); tells it to send, it doesn't actually finish sending instantaneously. If you put a sleep(0.5); after the flush, there is a much better chance of finishing.

A better solution might be to write a program to use in place of sudo reboot that closes its input and output, sleeps half a second, and invokes the sudo reboot. This will allow the web page output to actually finish before the reboot starts. Perhaps something like:

#include <unistd.h>
#include <stdlib.h>
#include <fcntl.h>
int main()
    int i;
    for (i=0; i<1024; i++) close(i);
    open("/dev/null", O_RDONLY);
    open("/dev/null", O_WRONLY);
    open("/dev/null", O_WRONLY);
    /* system("/usr/bin/sudo /sbin/reboot"); */
    execl("/usr/bin/sudo", "sudo", "/sbin/reboot", NULL);
    return 0;

Wouldn't this do the job ?

sudo shutdown -r -t 5

Reboot after a delay of 5 seconds.


Thank you all for your responses. I solved it with:

 exec("sudo reboot > /dev/null 2>/dev/null &");

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