How to run a command remotely
 

I can run this command successfully over ssh.

#/usr/bin/mplayer [options]

I want to be able to do the same using PHP.

But doing the following inside a php script does not work:

exec("/usr/bin/mplayer [options]");

I know the php's exec() works, since the following worked when I tried it:

exec("echo '/usr/bin/mplayer [options]' > /tvoutput");

So, I concluded that it must be that apache, which my web server runs as must not have permission to run the command /usr/bin/mplayer.

I then added apache to sudoers file.

But then this still doesn't work:

exec("sudo /usr/bin/mplayer [options]");

If I can issue
/usr/bin/mplayer [options]
from an ssh terminal and get the desired effect, I'm just baffled as to why I can't do it via a PHP script.

This is obviously not a PHP issue, since the command is being handed to linux correctly.

Any ideas? Sorry about the long explanation.

Thx.

This sounds like SELinux saving you from yourself. To verify check your /var/log/messages or /var/log/audit/audit.log for AVC denied messages. You can also temporarily disable SELinux to test with (as root):

setenforce 0

If it works, then you can re-enable SELinux with:

setenforce 1

You'll either need to create a local policy to enable execution, or check the booleans under menu System->Administration->Security Level and Firewall on the SELinux tab, HTTPD Service. One of the booleans may allow you to do what you are trying to accomplish.

I'm having EXACTLY the same issue running a shell script from PHP, because the shell script needs to modify some of root's files.

# setenforce 0
setenforce: SELinux is disabled

You may look into modifying the sudoers file to allow a particular user on your system to temporarily run as root.

I think it goes something like this:

your_non_root_user ALL=(root) NOPASSWD: /command/to/run

Although people say it's not advisable to allow a user to run as root, but you can restrict the permission to just a single command as shown above.

OK, now that you have disabled SELinux, test your code.

It wasn't enabled before. That's why I posted the ouput of the command.

Sorry, I was distracted. I see that SELinux is disabled.

Thank you for trying.
If you have other ideas, please share.

Is there a way to know if an error message is returned?

tail /var/log/messages shows nothing related to it.

Well, if you are running through your web browser, the error logs in /var/log/httpd/ should indicate any errors that were encountered.

You're correct. /var/log/httpd/error_log has this

sudo: sorry, you must have a tty to run sudo

After a little searching online, I found out FC6 has added more restrictions to sudo:

Defaults requiretty

I commented that out, and am no longer getting any errors in error_log, although my command still won't run.

I'm one step closer, thanks to you, but not quite there yet.

The next question I would have is, are you specifying the display (apache doesn't have one)? For example, if you are sending the video to your TV, the second head on your video card:

...mplayer -display :0.1 ...

I've been using:
DISPLAY=:0.1 /usr/bin/mplayer

instead of your suggestion of:

/usr/bin/mplayer -dispaly :0.1

Anyway, after brooding over a few more hurdles, I finally go it to do what I wanted.

You've been a tremendous help. Not being formally trained in linux is a challenge for me. But with guys like you, and my resilience, it often works out in the end.