diff --git a/docs/source/faq.rst b/docs/source/faq.rst
index 74cd50042..64b44c905 100644
--- a/docs/source/faq.rst
+++ b/docs/source/faq.rst
@@ -129,9 +129,13 @@ One of the first settings that usually needs to be bumped is the maximum number
 of open file descriptors for a given process. For the confused out there,
 remember that Unices treat sockets as files.
 
-::
+.. warning:: ``sudo ulimit`` may not work
+
+Considering non-privileged users are not able to relax the limit, you should
+firstly switch to root user, increase the limit, then run gunicorn. Using ``sudo
+ulimit`` would not take effect.
 
-    $ sudo ulimit -n 2048
+Try systemd's service unit file, or an initscript which runs as root.
 
 How can I increase the maximum socket backlog?
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