Shell Programming and Scripting

Hi all,
I want to execute a shell script in which I call ssh to execute a remote command.

Everything works fine from command line but when I try to call from PHP (with exec or whatever function) it fails.

After some time I came to the root cause: when www-data execute the ssh command it asks for key-exchange/password even if "ssh -l myuser R_HOST ...".

I'm not a pro with ssh, can you help with some tip?

Thanks,
Evan

The -l myuser flag says, which user to use on the remote end, not the local end. Also, since the directory ~/.ssh is not group/world readable, www-data would not be able to read myuser's private key.

You have to generate a keypair for www-data on the local host and paste www-data's public key into myuser's autothorized_keys file on the remote host.

Thank you hergp for quick reply.
It works but ...

Is it possible to use the -i option specifiyng the myuser id_rsa.pub file?
I tried but I get some errors about file permissions and even copying the id_rsa into www-data .ssh's directory it doesn't work.

This way I can prevent www-data to access remote host unless I specify the id_rsa.pub right? Does this make sense?

By design, the ~/.ssh directory must not be readable by anyone else but the owner. So www-data would not be able to read my_user's private key. If the permissions are set differently, ssh refuses to use the key.

You could copy my_user's keypair into www-data's ~/.ssh directory (changing the owner of the file to www-data). But then you could no longer tell www-data apart from my_user on remote computers and www-data would have access wherever my_user has access. So I advise against doing this, unless you exactly know what you are doing. By the way, it is not such a big effort to create a keypair for www-data and put the public key in my_user's authorized_keys file on the remote computer.

Ok thanks hergp, I followed your advice.

Kind Regards,
Evan