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Question

Owner of NGINX process

Posted November 7, 2017 33.4k views
NginxUbuntuSecurityUbuntu 16.04

Hi there!

I’ve just installed nginx and wondering why there are two processes.
One process is owned by root, the other one is owned by www-data.

PID  USER      PR  NI    VIRT    RES    SHR S %CPU %MEM     TIME+ COMMAND
7017 root      20   0  124972   1432     80 S  0.0  0.3   0:00.00 nginx                                                                                       
7018 www-data  20   0  125332   3168   1588 S  0.0  0.6   0:00.00 nginx

I didn’t changed the nginx.conf yet, so the configured user is still www-data.

Is it correct that one process is owned by root? Is that a security risk I need to worry about?

Thank you very much!

  • Matthias
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mhampel
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mhampel

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3 answers
acicali May 16, 2020

A bit of clarification - only the root user can listen on ports less than 1024. This is for security reasons, otherwise system users could eavesdrop on each other.

Since web traffic is typically hosted on ports 80 and 443, a web server actually needs to run as root in order to listen on and server traffic over those ports.

To reduce the attack surface, increase stability (and probably other reasons) NGINX runs one parent process as root. The parent process manages spawning child processes as well as passing requests off to them. This means that the actual process that handles each request is non-root and less privileged.

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jonleibowitz November 7, 2017

The process owned by root is the nginx parent process. This process forks worker processes which are run by the user defined in nginx.conf.

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Elizine November 8, 2017

The nginx process is running as www-data, so, the root:www-data ownership would only work with group write permissions set. There is no major issue with running with your web files owned by www-data:www-data but if you are concerned you could give ownership of wp-content to www-data and leave the rest of the install as root:www-data.

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