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Satanowski
Asked: 2010-05-12 02:37:08 +0800 CST

Apache+PHP problem: Cannot list processes other than apache's

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I have a quite fresh install of the Apache (2.2.3/Centos) + PHP(5.1.6) and following problem: I need to monitor life of one process and in order to do that I run:

$last_line = exec('ps -C snmpd');

and check its output.

Unfortunately I always get nothing. I've checked it with other process names and it seems it can 'see' only Apache's processes.

Any idea how to work this out?

UPDATE: Execution of the other command system('snmpget -v2c -c public localhost '.$oid, $retval); works great, there is only problem with the ps. What is strange (for me), when I log as apache user and run ps manually it works correctly (shows everything).

apache-2.2 process php5

4 Answers

  1. You will only be able to see the processes of the user under which the web server is running, as this is the user exectuing the command.

    If you require the ability to run commands as a different user, have a look at suexec. http://httpd.apache.org/docs/2.2/suexec.html

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  2. Try running a fuller ps call like:

    ps aux | grep -i snmpd | grep -v grep
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  3. You might also use backtick operator to achieve the same thing. I confirm it works while exec doesn't.

    $out = `ps -aux|grep pianobarfly|grep -v grep`;

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  4. Probably selinux. SELinux restricts the domain that httpd runs in so it can only view its own processes.

    You can either:-

    1. Turn off selinux (wouldnt recommend that) - setenforce 0
    2. Make httpd not use selinux (not recommend that either because httpd is a likely attack vector) setsebool -P httpd_disable_trans = 1. Restart httpd.
    3. Change the policy to permit seeing processes in /proc.

    This should do it:-

    policy_module(myhttpd,1.0.0)

gen_require(`
    type httpd_t;
')

kernel_read_system_state(httpd_t);

    Install selinux-policy-devel from yum.

    Then run the command "make -f /usr/share/selinux/devel/Makefile load" to insert the new module.

    You should see an immediate result.

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