How to execute remote SSH command in background using PHP exec()?

Question

Is there a simple way to execute SSH commands in the background on remote machines from PHP without using ssh2_*? The PHP script is executed by the user from bash (no Apache involved), so it's not an issue of rights. I've tried doing this:

exec("ssh -f -o UnknownHostsFile=/dev/null -o StrictHostKeyChecking=no -i {$keyFile} {$user}@{$ip} {$remoteCommand} 2>&1 >/dev/null </dev/null");

For example:

exec("ssh -f -o UnknownHostsFile=/dev/null -o StrictHostKeyChecking=no -i /home/data/id_rsa user@192.168.0.19 '/home/user/script.sh ; exit' 2>&1 >/dev/null </dev/null");

All PHP variables have been escaped with escapeshellarg() and $remoteCommand is a bash script on the remote machine that sleeps for a few minutes and then starts executing some commands.

My problem is that if I execute that SSH command from bash, it gives control back to bash immediately. If I execute it from php using exec() it waits until the remote command executes. I've tried adding 2>&1 >/dev/null </dev/null after /home/user/script.sh, but the execution still doesn't return control to the PHP script.

I don't understand the problem with bash. Don't you want it to give control back to bash immediately? Aren't you trying to execute in the background? — davidethell, Dec 13 '11 at 10:19
If you don't mind elaborating, why don't you want to use ssh2_*? — favoretti, Dec 13 '11 at 10:20
@favoretti I have used it before and it is something I would like to avoid. — f.ardelian, Dec 13 '11 at 10:22
Have you seen this? http://stackoverflow.com/questions/45953/php-execute-a-background-process — favoretti, Dec 13 '11 at 10:31

score 1 · Answer 1 · answered Dec 13 '11 at 10:22

1

I think you are missing an & at the end of your command for sending the execution to the background.

answered Dec 13 '11 at 10:22

macjohn

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Yes, I was missing that, but it still didn't help. – f.ardelian Dec 13 '11 at 10:24

How to execute remote SSH command in background using PHP exec()?

1 Answers1