I'm trying to send input to a screen session from php. So far I have followed the steps explained here Is running GNU Screen suid root the only way to make multiuser mode work? And I have set "multiuser on" and "acladd www-data" in the screenrc file (or well, no. in another file that I use by the -c option but still) My problem now is that whenever i try to acess screen by php exec('screen -S user/session -p 0 -X stuff "test"'."\n", $ret); I get the error: Cannot opendir /var/run/screen/S-user: Permission denied